MAIN\nENGINE STATUS REPORT September 24, 2002<\/strong><\/p>\n\n\n\n Jan A. Verbruggen<\/p>\n\n\n\n <\/p>\n\n\n\n Contents<\/strong><\/p>\n\n\n\n Note on edition<\/a> This\nreport supersedes the December 18, 2001 version. Nontrivial changes are in red.\nIt has been prepared in English to facilitate international discussion.<\/p>\n\n\n\n The\nproject was essentially completed when the engine was officially restored to\nmotion at an inauguration ceremony on 4 June 2002. As a consequence, this\nstatus report is now finalized; future changes will mainly correct errors or\nclarify aspects.<\/p>\n\n\n\n No\napology is made for the length of the report. It is intended as a coherent\nrecord and \u2013 judging from past experience \u2013 future generations are more likely\nto find it lacking in detail than anything else …..<\/p>\n\n\n\n The\nCruquius engine stopped working in November 1932. On 10 June 1933 she was\nsteamed one last time, for a closing and preservation ceremony. In March 1982\nthe Cruquius Trust council agreed to establish a working group to study the\nfeasibility of making the engine move again. First of all, various ways to drive\nthe engine were compared. It was decided to attempt hydraulic drive. Next, a\nnumber of aspects of the building and engine were investigated to see if these\nwould permit motion. In a number of cases this entailed quite extensive\ncleaning or dismantling operations.<\/p>\n\n\n\n All\nactivities and findings were fairly extensively recorded, both photographically\nand in writing. This report is primarily the written record of the\ninvestigating, cleaning, repair, and restoration activities. Most details of\nthe hydraulic project will eventually be the subject of a separate document.<\/p>\n\n\n\n It\nis assumed that the reader has some knowledge of how a Cornish engine works, so\nthe following account is kept very brief. A Cornish engine is a single-acting\nnonrotative vertical steam engine, in which steam and vacuum lift a dead weight\nduring the first half of the stroke. During the second half of the stroke the\nsteam piston is in equilibrium (i.e. the spaces on both sides communicate via\nthe open equilibrium valve<\/em>) and the weight descends, using its\ngravitational energy to operate the pumps. In the most widespread type of\nCornish engine, widely used for mine drainage, the steam cylinder and the\nweight are at opposite ends of a rocking beam<\/em> or bob<\/em>. The weight\n(consisting mostly of the pump rod hanging down a deep shaft) is at the beam’s\n\u201coutdoor\u201d end and is pulled up<\/em> by admitting steam above<\/em> the\npiston at the other end (indoor<\/em> or steam <\/em>stroke). During the\nfollowing outdoor<\/em> or equilibrium <\/em>stroke the descending weight \npushes down<\/em> the plungers of force pumps which, in a mine, are arranged\nin series for additive lifts.<\/p>\n\n\n\n Cruquius\nhas lift (bucket) pumps in parallel for additive capacity, and the weight must pull<\/em>\ntheir pistons up<\/em>; consequently it is at the indoor<\/em> end of the beams, above the\nsteam cylinder. To lift the weight, steam must now be admitted under<\/em> the\npiston, i.e. the engine is inverted<\/em>. Another peculiarity of this engine\nis, that there are two cylinders: a 213 cm (84″) HP cylinder built inside<\/em> \na 366 cm (144″) annular LP one. During the ‘equilibrium’ stroke only the\nHP piston is actually in equilibrium; the downward pressure differential on the\nLP piston is added to the gravity action of the weight. Because the steam\nexpands in two stages, this is a combined<\/em> or compound<\/em> \nengine and, strictly speaking, no longer fully single acting [1].<\/p>\n\n\n\n In\nthe course of the preliminary studies in the early 1840’s, the consultants\nGibbs & Dean produced 25 drawings, most of which survive in the polder\narchives; these are historically important, but certainly not representative of\nthe Cruquius engine as built.<\/p>\n\n\n\n In\n1988 P. van Putten found an incomplete set of ‘contract drawings’ for Cruquius\nand Lynden in the polder archives. These had probably been made by the\nconsultants, and the manufacturers (Harvey, Fox and van Vlissingen) would\nprobably have produced their own shop drawings. Nevertheless, these contract\ndrawings \u2013 which show signs of heavy use \u2013 are undoubtedly a close\napproximation of the Cruquius as built. They confirmed many observations made\nduring recent inspections, and they revealed several hitherto unknown details.<\/p>\n\n\n\n After\nthe Harvey & Co. works in Hayle (Cornwall) closed in the last quarter of\nthe 19th century, the drawing office seems to have been left largely\nundisturbed until its contents (including many drawings) were destroyed in the\n1950’s. It must be assumed, that workshop drawings of Cruquius no longer exist.<\/p>\n\n\n\n In\n1988 A.J. Engel found a little notebook [2] with operating and\nmaintenance notes for the period 1924-1932. The polder archives may hold more\nsimilar notes.<\/p>\n\n\n\n At\nthe outset of restoration work of any kind this is an important question. Any\nobject has a history of modifications, and so it has existed in more than one\nstate. One of these must usually be selected as a basis for restoration.\nFortunately, for Cruquius the choice is easy. Modifications to the engine have\nbeen few and minor. Issues such as \u201cShould we reconnect the 8th pump ?\u201d or\n\u201cWill we shift the steam slide back to its original position ?\u201d are not\nfundamental. The only major changes occurred in the boiler house: two wings\nadded in 1860, full reboilering in 1888\/1890, cleared out c.1936. Restoring the\nboiler house to any of the states prior to 1936 is virtually out of the\nquestion, so here the selection problem is largely academic.<\/p>\n\n\n\n Four\nalternatives were considered: steam, compressed air, hydraulic and electric\ndrive. Each of these is discussed below. Eventually modern mineral oil\nhydraulics (see 1.4.2) was chosen.<\/p>\n\n\n\n This\nwould obviously be historically ideal, technically attractive, and spectacular.\nIt would also mean installing a substantial steam supply, restoring all<\/em><\/strong>\nparts of the engine to full working order, and the need for qualified (and\nprobably paid) operating and maintenance staff. Apart from the steam supply,\nmajor hurdles would be the soft piston packings, the piston rods and\n(possibly) the entire condenser. The cost \u2013 both initial outlay and annual\noperating expenses \u2013 would be very high, and there would be serious space\nproblems as well: how can a steam supply be housed, without sacrificing a\nsubstantial part of the museum space, in a way acceptable from preservation,\nmuseum, engineering and planning viewpoints ? <\/p>\n\n\n\n Would\nnon-condensing operation be feasible? Possibly, but it would mean exhausting to\nthe atmosphere, i.e. making a hole in the condenser and a pipe from there to\noutside the house, a modification which \u2013 apart from being impractical and\nunsightly \u2013 would unacceptably damage the engine. Occasional steaming, as practised at several steam\nmuseums, would necessitate addressing the problem of conservation during idle\nperiods, e.g. by filling the system with nitrogen. Driving a Cornish engine is\na highly skilled job, mistakes can seriously damage the engine and building.\nTraining facilities for Cornish engines are not available in Holland; a course\nat Kew Bridge Steam Museum in London would appear to be the only possibility.\nFor occasional steaming, at least two or three fully qualified drivers would\nhave to be available.<\/p>\n\n\n\n As\na consequence, steam is considered not to be a realistic short or intermediate\nterm goal. However, an important touchstone for any other solution must be,\nthat it not block the way for possible future steam plans. Some measures had to\nbe taken, and modifications made, which would have to be undone if steam\noperation were to be attempted in future. These are listed in Sect. 11.<\/p>\n\n\n\n Additional\nnote 1998\/1999 about steam supply.<\/em> In view of recent discussions and\nchallenges, some aspects of the steam supply may be further elaborated.<\/p>\n\n\n\n Like\nmost Cornish pumping engines, Cruquius worked at stroke rates of a few up to\nseven or eight per minute, at steam (gauge) pressures in the 2 to 4 bar range.\nSteam was wet or saturated (certainly not superheated), at c.140-160 \u00b0<\/sup>C. Steam would be\nadmitted only during the steam half-stroke, for about one second, i.e. for\nabout 10% of the ten-second full-stroke duration (at six strokes\/minute). In\nthe Cruquius engine the quantity of steam admitted would originally have been\nc.50% of the HP or central cylinder volume, later almost doubled. For this\nlater case, the average steam consumption of Cruquius has been estimated at c.7\nto 10 tons per hour, as a consequence the peak rate would be about\n70-100 t\/h. Steam was supplied by coal-fired boilers of the Cornish or\nLancashire type: 1849 six Cornish, c.1860 ten Cornish, 1888 six larger\nLancashire. These boilers have a large water space. Their combined steam space\nis also considerable \u2013 a rough estimate would be 70-80 m3<\/sup> \u2013\nproviding some buffering for the irregular steam consumption, but not enough.\nOver the boilers, occupying the full width of the boiler house was a steam receiver\nof c.2 m diameter, roughly doubling the buffering capacity. Even so, the\nstrokes of the engine were reputedly reflected in level fluctuations in the\nboilers\u2019 water gauges.<\/p>\n\n\n\n The\nfinal set of boilers was removed c.1935; only vestiges of their foundations\nremain. The boiler house was eventually converted to museum space.<\/p>\n\n\n\n Re-creating\na close approximation to the original (1849, 1860 or 1888?) steam supply would\nmean moving the museum elsewhere. Obtaining a suitable set of boilers\nsecond-hand is out of the question. New boilers would have to be made, their\ndesign necessarily a compromise between \u201cold\u201d appearance and modern safety\nrequirements. <\/p>\n\n\n\n Forget\nabout recreating a 19th-century boiler house, then, and supply steam with\nmodern boilers? Such boilers are more compact, and they invariably have much\nhigher pressure, e.g. 15-40 bar. Special throttling valves can reduce pressure,\nbut the result would be superheated steam at temperatures unsuitable for a\nCornish engine (packing, gaskets, condenser etc.). Steam conditioning by water\ninjection is probably possible (special \u2013 and expensive \u2013 reducing valves). The\nirregularity problem could most likely be solved by adding an immense steam\naccumulator (c.50 m3<\/sup> would appear to be a minimum). A modest-sized\nboiler and reducing valve would then suffice, but the space needed for the\nentire steam plant would be huge. As an aside, it may be noted that a type of\naccumulator exists, which stores steam in the form of pressurized water at\nboiling point. This is much smaller, but only suitable for highly fluctuating\nsteam input and fairly constant output \u2013 just the reverse of what is needed\nhere.<\/p>\n\n\n\n The\nsteam supply alternatives discussed above, all appear to be technically\nfeasible (but each would need considerable further study). Other aspects, such\nas planning and cost, are much more problematic.<\/p>\n\n\n\n Air\nhas similar supply and space problems. An advantage would appear to be, that a\nfully functional condenser is not needed, but \u2013 as for non-condensing steam \u2013 a\nsubstantial exhaust would have to be made. It might be considered to release\nthe exhaust air indoors, and then one way to do this might be to remove one or\nboth covers on the connecting ducts between the condenser and air pump barrels\n(in the condenser cistern; these covers provide maintenance access to condenser\nfoot valves). Apart from the condenser, however, all engine parts must be\nrestored to full working order, as for steam. P. Stokes [3] has proposed\nthe use of vacuum via the exhaust. Conceivably, a vacuum pump could be\nconnected to one of these foot valve access openings. This would create\ndifferent (but not easier) space problems. Otherwise such vacuum operation\nwould not differ much from the use of low-pressure compressed air. The relative\nmerits of air and vacuum might be analyzed via computer simulation (which may\none day become available).<\/p>\n\n\n\n There\nis one Cornish engine which is occasionally operated on air for the\npublic : Parkandillick engine near St. Austell, Cornwall. This 1,26 m\n(50″) engine pumped china clay slurry from a rather shallow shaft, using\nan outdoor bucket (lift) pump. This mode of operation, where the steam stroke\nis also the power stroke of the pump, differs fundamentally from the more usual\n\u201csteam lifts weight, weight operates pump\u201d mode. The (outdoor) surplus weight\non this engine serves mainly to return the pump and steam pistons, and\nconsequently it is much less than on a mine pumping engine.- there was even a\nbalance bob to partly compensate for the excess pump rod plus piston weight.\nThis balance bob has been removed, and the pump rod cut, leaving an outdoor\nweight surplus of c.4 tons. The Parkandillick engine now runs quite well\non air of very low pressure (c.0.3 bar or 4 psi). The speed can be reasonably\nrealistic, because the moving mass is now quite low. This or a similar approach\ndoes not appear feasible for Cruquius.<\/p>\n\n\n\n An\nelectromechanical drive to a reasonably central point does not appear to be\npossible without unacceptably destructive intervention (such as making a big\nhole in the double cylinder bottom). An advantage would be, that engine\ncomponents would not have to be fully functional or tight, just movable.<\/p>\n\n\n\n Hydraulics with standard components offers the same advantage, and requires less space than an electric drive for the actual drive components (cylinders), and there is considerable freedom in the location of the power pack and associated components. Finding a suitable and not-too-conspicuous location for the long drive cylinders would be quite a problem, however. It has been suggested that they be concealed in the outdoor pump barrels; other considerations apart, however, these are standing directly on the wooden foundation floor (see Sect.2.1), and cannot take the required upward force. Therefore two other possibilities have been considered.<\/p>\n\n\n\n 1.4.1<\/strong><\/p>\n\n\n\n Use part of the existing passive hydraulic (buffer) system, see fig.1. This subsystem was installed to prevent shock due to uncontrolled closing of the water pump bucket valves at the end of the steam stroke when the weight has reached its top position. This position is \u2018locked\u2019 for a suitable period (a couple of seconds) to allow the bucket valves to close. During the up (steam) stroke, two 225 mm (9″) dia. plungers or rams, attached to the ears of the central weight, draw water from standpipes via check valves. The water column locks the weight in its top position until a bypass valve is opened simultaneously with the engine’s equilibrium valve. A butterfly type governor valve in the bypass connection may have aided control of the equilibrium stroke speed. This valve is now fully open, and its operating control was removed long ago (see also Sect.3.3 and Sect.10). <\/p>\n\n\n\n If\nthis system could be connected to a (water) hydraulic power source via nozzles\nto be made on the HP and LP connecting pipes, it might be possible to use the\nexisting plungers to move the engine. The plungers would have to be fully\noperational and all hydraulic joints and packings would have to be tight. The\nexisting hydraulic valves would have to be secured in their closed positions\nand made reasonably tight. Closing shut-off valves on the nozzles, and freeing\nthe check and bypass valves, would restore the original situation and enable\nthe system to be used for its original purpose, e.g. in a future steam scheme.<\/p>\n\n\n\n 1.4.2<\/strong><\/p>\n\n\n\n Mount\nstandard hydraulic cylinders \u201cparallel\u201d to the buffer rams, i.e. between the\nengine foundation and the weight ears, and use standard mineral oil hydraulics.<\/p>\n\n\n\n Much\neffort has been put into investigating the water hydraulics scheme, and the\nfindings have been extensively recorded. Eventually, and partly due to the\nproblems envisaged, this idea was abandoned in favour of mineral oil\nhydraulics. The design etc. of this solution is documented elsewhere. <\/p>\n\n\n\n The\n1846 building specification called for the engine building basement to be\nconstructed as a dry tub<\/em> with bottom and walls executed as watertight\nmasonry (brick in tarras mortar).<\/p>\n\n\n\n The\nentire building structure rests on pile foundations at two levels: the boiler\nhouse \/ exit channel level (high, not further discussed), and the engine-house\n\/ pump \/ chimney stack \/ retaining wall level (low). The tops of the piles are\ncoupled by a massive timber grid: capping beams<\/em> (running E-W, or\nparallel to the polder dike, Dutch kespen<\/em>) link the tenoned top ends of\nthe piles, N-S running grating beams<\/em> (Dutch kloosterhouten<\/em> or schuifhouten<\/em>)\nare cross-cogged to the capping beams and link them to form a sturdy grid\n(note: the terms in various dictionaries differ). Between these grating beams a\n10 cm thick floor is laid in two layers on the capping beams, about\n1.5 m below polder level. All masonry rests on this floor. The density of\nthe piles (and of the coupling grid) is increased where the loads are heaviest,\ni.e. under the central engine house and the chimney stack, and under the eight\noutdoor pumps. Here, also, the timber structure is part oak, the remainder\nbeing pine.<\/p>\n\n\n\n From\nthe illustrations in [17] it would appear that the height of the grating\nbeams exceeds the floor thickness, i.e. those beams would stand proud of the\nfloor, and where these \u201cridges\u201d interfere with the pump supports (lantern\npieces, see Sect.8) the grating beam top portion would be cut away. The\nbuilding specification is not fully clear on this, close inspection in\nconnection with work on the pumps (see Sect.8) does indeed reveal the\nridges.<\/p>\n\n\n\n The\nbrick floor of the lower engine house basement is c.0.5 m thick, and is\nthus about 1 m below polder level. On this floor stands the central engine\nfoundation block with inspection access to the bottom ends of various\nanchor bolts via tunnels (see Sect.2.2). This c.5 m tall brick pedestal\nis of oblong shape and is covered by a stone slab (in several pieces) which is\nthe cylinder loading or bedstone. At the long ends recesses have been left to\nmount the hydraulic plunger housings abt. 1 m lower than the cylinder. The\nspace in these recesses between the housings and the main block was later\nlargely filled with brick masonry; this was much deteriorated and the\noriginal shape and purpose of this brick infill can only be guessed at (see\nSect.3.1). Most of it has been removed for inspection of the plunger\nhousings.<\/p>\n\n\n\n The\noblong pedestal stands within the circular engine house wall and leaves two\nlarge and two smaller crescent-shaped basement sections; one of the large ones\nis largely occupied by the condenser cistern, which is supported by three brick\nconnecting walls. The space between these appears to be inaccessible.<\/p>\n\n\n\n In\n1983 the other three basement sections were found to be largely filled with\n‘rubbish’, which turned out to be mainly a thin black mud drying to dark\ngrey. About 1 m above polder level an overflow hole in the outer wall was\nfound. The ‘dry tub’ had apparently become a rubbish dump and a water\ncollecting basin, where everything up to the overflow level was immersed in\n(somewhat corrosive) mud. As a result access to the inspection tunnels was\nblocked, and even the position of the entrance to these tunnels could no longer\nbe located.<\/p>\n\n\n\n In 1985 volunteers removed, bucket by bucket, about ten m3<\/sup> of mud and rubbish, and uncovered the inspection tunnels. Very few objects were found: a small elliptical cast iron weight which used to keep the equilibrium pipe drain cock normally closed, a larger one for a long-disused spindle lever on the hydraulic valve body (see Sect.3.3 for details), a spanner, a glass bottle, fragments of gaskets, shoes etc. <\/p>\n\n\n\n The following sequence of events appears likely:<\/p>\n\n\n\n Nothing\nhas yet come to light to ascribe these events to anything but technical ignorance.\nIt should be borne in mind that the mechanical engineering staff of even a\nlarge polder such as Haarlemmermeer was minimal. <\/p>\n\n\n\n R.L.\nHills has commented [6], that the steam jacket could not do much for the\ncentral HP cylinder anyway, so that its beneficial effect was at best marginal,\nand disconnecting would not have had much detrimental effect on efficiency.<\/p>\n\n\n\n The\ndrains no longer operate, and the rainpipe has now been rerouted. To make the\nbasement once more the ‘dry tub’ it was designed to be, all that needs to be\ndone is to close two cracks in the basement wall at the North (canal or boiler\nhouse) side, through which some water still seeps. Final cleaning could then be\ncarried out.<\/p>\n\n\n\n The\ncylinder foundation is an oblong block of brick masonry about 4 m high, capped\nby a 0,4 m thick stone slab (built up of several pieces) measuring about\n4,5 by 6 m overall. The complex cylinder bottom casting (with steam jacket\nspace, and steam and equilibrium conduits) rests on this loading. At its outer\ncircumference this carries the LP cylinder, the double bottom flange of which\nis held down by thirteen wrought iron 1-1\/2″ bolts of about 4,5 m long.\nThe HP-LP separating wall is secured by four similar bolts. The latter would\nseem to be rather light anchoring for an engine this size, but it should be\nremembered that this is an inverted engine where the working load on the\ncylinder foundation is always downward (the permanent condenser vacuum under\nthe annular piston tends to pull the bottom up, but the weight of the\ncylinder-plus-covers by itself is more). On the same grounds, frequent\ninspection and retightening of these bolts seems less essential than in Cornish\npractice. Some of the bolts are hidden, e.g. between the cylinder and the\ncondenser cistern, and are not accessible for maintenance or retightening. All\nbolts extend down through cast iron plates embedded in the masonry. At their\nbottom ends they are fitted with cotters, at the top they are tightened with\nnuts. Under the LP bolts is an annular inspection tunnel approx. 1,1 m high and\n0,6 m wide. The HP bolts are in recesses in the central cylindrical inspection\nspace of about 1,6 m diameter which extends over the full height of the\nfoundation block. It is not possible to replace them with the cylinder in\nplace. Clearly the designer intended the bolts to last the life of the engine.\nThe foundation block itself is built on a 0,5 m thick brick floor, which rests\non the wooden pile foundation structure.<\/p>\n\n\n\n Due\nto the circumstances described in Sect. 2.1 the water\/mud level in the\nbasement had blocked access to the inspection spaces, and had immersed the\nbottom half meter or so of the bolts, since about 1890. It was not surprising\nto find, after the cleanout operation, two corroded anchor bolt bottom ends standing\non the floor of the inspection tunnel<\/em>. As it was not possible to assess the\ncondition of the other eleven with certainty, it was decided for safety reasons\nto remove as many as possible. The top ends were cut \n(oxyacetylene), the bolt was forced down, and meter after meter was cut off in\nthe tunnel. The top ends of the 3 bolts at the south side are behind the\ncondenser cistern and thus inaccessible for cutting. All that could be done\nhere was hammering and trying to pry loose the bottom end, to try and make sure\nthat the bolt was still hanging by more than a ‘hair’.<\/p>\n\n\n\n Eventually\nsome or all of the anchor bolts will have to be replaced; a suitable method\nappears to be: use 1 m lengths of standard threaded rod with coupling muffs not\nexceeding 1 1\/4″ dia., build these upward from the inspection tunnel and\nfit them with replica top and bottom ends. Commercially available M24 rods and\nmuffs appear suitable. Strength is not an important issue, and modern bolt\/rod\nmaterials such as 8.8 are far stronger than wrought iron anyway.<\/p>\n\n\n\n The cylinder foundation block carries two pairs of cast iron columns (see fig. 2) which support the two main beams at the cylinder floor level, plus upper columns. Between each pair, the wooden beam is reinforced by two iron plates. This reinforced section supports the cast iron pedestal which carries the crosshead (weight cap) parallel guide rods and holds the lower buffer stop. The lower columns are pre-compressed by 125 mm (5″) dia. tension rods which run from this pedestal down into the foundation block. Their cottered bottom ends \u2013 now rather corroded \u2013 are in recesses in the outer wall of the inspection tunnel.<\/p>\n\n\n\n A\ndetailed assessment of the condition of these tension rods has not been made,\nas they seem not to be overly important for the engine operation\nenvisaged.<\/p>\n\n\n\n As\nfig. 2 shows, the column ends are ‘cradle’-shaped. At the cylinder floor level,\nhowever, most of the cradle sides are broken off; at the southeast column a\nrepair with clamps and straps has been carried out, elsewhere nothing was done.\nThe damage would appear to have been caused by severe shocks. Overstroking\ncomes to mind (see the remarks in Sect.9 about starting problems to be\nexpected for a late cutoff engine), but vertical jolts would have to be violent\nindeed, to cause fractures in these places. See Sect.10.9 for the likely\ncause.<\/p>\n\n\n\n The\noutdoor pumps (see Sect.8) stand on the\nfoundation floor (see Sect.2.1), their upper portions\nprotruding through a 10 cm (4\u201d) thick oak floor, which is the bottom of a\nlaunder running around the pump side of the engine building. This collar\nlaunder<\/em>, connects to two channels running to the front of the building and\nthrough the dike into the encircling canal of the polder. The pumps discharge\nonto this collar launder, where the level is normally the same as in the canal,\ni.e. c.1.5 m (5ft) above the floor. The potential breach in the dike \u2013\nwhich might cause canal water to flow back into the polder in case of a serious\nstructural collapse \u2013 is secured by two sets of automatic sluicegates<\/em> at\nthe junctions between collar launder and channels. One gate of each set has a paddle<\/em>,\nand can also be latched in the open position. We reckon this provision probably\nserved two purposes:<\/p>\n\n\n\n The\ncollar launder floor, which had deteriorated rapidly after the closing down of\nthe pumping station, has been restored in simplified form, without hatches,\nwith reduced thickness (8 cm) and fewer supports, allowing water-filling\nit to a depth of c.50 cm (20\u201d). One of the quite badly deteriorated\npaddled gates has been removed and cut up, with the intention of discarding\nit. Volunteers have rescued the seriously damaged remains, and are currently\nrestoring this gate. It should be noted, that the discharge channel to the\noutside canal was largely filled in, as a safety measure after Cruquius had\nbeen decommissioned in 1932, so the sluices can no longer perform their\nfunction.<\/p>\n\n\n\n Note:\nmuch of this Section resulted from the investigation of the feasibility of\nwater hydraulic drive (see Sect.1.4.1). The later decision in favour of\noil hydraulics results in many of these findings and observations now having\nmainly historical interest, and less practical value for restoration.<\/p>\n\n\n\n The\npurpose and operation of the hydraulic has been explained in Sect.1.4.1.\nIn the operational period the static pressure in the system would be about 80\nbar (assuming a weight of 65 tons); peaks of about 120 bar have reputedly been\nobserved. By reducing the load, it should be possible to move the engine with a\npressure of less than 50 bar (note that a Cornish engine cannot be operated\nwith zero load). In the course of the activities discussed below, the entire\nhydraulic system has been high pressure jet cleaned by the firm of Groenheide.\nEvidently the system can never be as clean as a modern hydraulic system has to\nbe.<\/p>\n\n\n\n For\nwater hydraulic drive, the 225 mm (9″) dia. plungers must be fully\nfunctional. A first endoscopic inspection via the air relief cock, just below\nthe stuffing box, revealed a surface that is somewhat rough, but not seriously\ncorroded. Surface inspection with a microscope confirmed the material to be\ncast iron. The surface is rather hard, but the coherence of the grains has\ndeteriorated in places, as chips can be chiselled off with surprising ease.<\/p>\n\n\n\n The\ntwo-tier bronze junk rings were easily lifted, but the bronze stuffing boxes\ncould not be removed from the tops of the housings: the 6 radial fixing screws\nresisted all attempts (brute force, penetrating oil, heat) at removal; one bolt\non the east housing eventually fractured. Subsequently the stuffing boxes were\nemptied, partly because it was hoped to create enough swing at the top for\nlifting out the 1 ton cast iron plunger at an angle (some 35 cm swing would be\nneeded). The approx. 15 mm wide stuffing chamber yielded mainly tightly\ncompressed braided hemp and asbestos fabric. A few layers further down, strips\nof leather were found. At a depth of about 140 mm a cup-shaped sheet brass ring\nrested on two more brass rings. These three metal rings were split; the two\nhalves of the bottom one were interlocked, the second ring was held together by\nsoft copper wire in a circumferential groove, locating pins on the top surface\nof this ring held the sheet ring halves in place.<\/p>\n\n\n\n The\nbottom of the stuffing box slopes inward. This indicates, that initially there\nwere no bottom rings. The first ring is shaped to fit this sloping bottom.\nAccording to [2] ‘the worn bottom rings were filed flat and two\n1\/8″ brass ring halves fitted on top’<\/em> in 1924.<\/p>\n\n\n\n These\nplunger packings, which had to seal against about 100-120 bar (1400-1700 psi)\nwater pressure, probably constituted one of the major maintenance and repair\nproblems of the engine. The notes in [2] show that, even during the\nstandby period, experiments with packing materials and arrangements were still\nbeing carried out. It is somewhat surprising that for a plunger with fairly\nrapid motion at high (cold) water pressure a hemp stuffing box should have been\nchosen. Hydraulic machinery \u2013 often working at similar water pressures \u2013 had been\nusing leather cup packings from the start (Joseph Bramah, c.1795), building on\npumping practice of at least 60 years standing [7]. The cup seal had\nproven reliability, did not require frequent retightening, and according to\ntextbook sources friction amounted to as little as one fifth of that of a\nstuffing box seal.<\/p>\n\n\n\n For\nthe time being, modern soft packing has been fitted, but if water hydraulic\noperation should turn out to be feasible, modern equivalents of the cup seal\nshould be considered.<\/p>\n\n\n\n Each\nplunger has an axial hole in its top end to receive a wrought iron bolt, fixed\nwith cotters. This bolt passes through a hole in one of the weight cap ears,\nand at the top a ‘head’ is formed by a ring secured with cotters. Both plungers\nwere disconnected from the bolts and lowered. The east bolt had been sealed so\nwell, that portions of its surface looked as if machined only yesterday. The\nswing obtained at the top was only about 1 cm, however. After raising the\nweight to its top position (see Sect. 4.1), the increased exposed length\n(and correspondingly reduced length in the housing), still allowed only about 5\ncm sideways movement. This means that the plunger cannot be lifted out and that\nit will have to be cleaned and dressed in place as far down as practicable; for\nwater hydraulic drive this implies a stroke shortening of about 20 cm to keep\nthe remaining rough parts of the surface below the stuffing box.<\/p>\n\n\n\n Most\nof the visible plunger surface is fairly smooth, with slight and quite evenly\nspread pitting, but with the remainder of the original surface substantially\nintact. The diameter varies slightly over the length (about 1 mm), but the\nvariations are very gradual; no circumferential ridges or steps are observed.\nThe obvious cause is wear.<\/p>\n\n\n\n Two\ndiametrically opposed faintly discernible ridges extend the full length and\nremind one of casting lines. This would be surprising, as these plungers were\nsurely machined after casting? The portion which was in the stuffing box when\nparked, shows circumferential areas of heavier pitting.<\/p>\n\n\n\n Near\nthe lower end, both plungers have a number of longitudinal ‘furrows’ of varying\nlength and depth. The largest is a few mm deep, about 1 cm wide and some 60 cm\nlong. Their cross section is rounded, and in some the deepest part has a rough\nsurface. The most likely cause of these furrows is erosion by water spurting\nthrough packing flaws during the short period at the end of the steam stroke,\nwhen the hydraulic is under high pressure (80 bar or more). (In [8]\nproblems with longitudinal grooves are mentioned for the large cast iron rams\nof the Anderton boat lift in the 1880’s; a report ascribed these to\nelectrochemical causes.)<\/p>\n\n\n\n Repair\nis essential to avoid excessive stroke shortening. Three methods have been\ndiscussed:<\/p>\n\n\n\n Regardless\nof the method chosen, substantial surface dressing would be required\nafterwards.<\/p>\n\n\n\n Flame\nspraying was chosen, and was performed by the firms of Metco and Griekspoor\nusing a high-nickel compound with chrome and moly. Subsequent dressing was done\nby volunteers, mainly by filing, using a three point bridge gauge set on an\nundamaged portion. The compound turned out to be not too hard, but very tough\nand difficult to file. Filing sounds like anathema for high pressure hydraulic\nparts, but in this case there seemed to be no other option short of dismantling\nthe entire weight structure. The results appear to be no worse than the\nundamaged areas. Remaining minor cracks and blemishes were filled with ‘liquid\nsteel’ epoxy, and dressed.<\/p>\n\n\n\n The\nsurface is far from ideal by modern hydraulic standards; in addition there is a\nslight alignment error which manifests itself by 1-2 mm lateral movement of the\nram in the gland over the stroke length. The following measures have been\ndiscussed. These may be combined, and they are relevant only for direct use of\nthe water hydraulic system as discussed in Sect.1.4.1.<\/p>\n\n\n\n 3.1.1<\/strong> Resurface the rams by\nmetallizing, by plating, or by fitting a sleeve. The latter might conceivably\nbe done in situ, although this has not been thought through in every detail,\nand may present unforeseen problems. Removal of the rams to a workshop is to be\npreferred, and this involves either dismantling of much of the superstructure,\nor cutting and rejoining the rams. The latter appears technically feasible.<\/p>\n\n\n\n 3.1.2<\/strong> Re-alignment of ram and\nhousing would involve extensive dismantling (i.e. disconnect, remove and\nre-align both the rams and their housings), or fitting a seal which can absorb\nthe lateral motion.<\/p>\n\n\n\n The\nhousings have a 60 mm thick bottom flange, with a 150 mm (6″) thick cover\nbolted on. The bolts have square heads which fit flush in square holes in the\ncover, with square nuts at the top. At least one of the bolts is missing. The\nforce to be withstood by this connection is the hydraulic pressure acting on\nthe narrow (5 mm) ring gap between plunger and housing, minus the weight of the\nhousing, plus the stuffing box friction. A crude estimate would be 50 to 100\nkN.<\/p>\n\n\n\n There\nare signs of corrosion everywhere, but mainly at the west side. The lower half\nmeter or so of the housing has lost about 10 mm wall thickness; the 5″\ntension rods are quite heavily corroded; the covers of the check valve housings\nare full of fairly deep valleys. Only pyramid-shaped vestiges remain of many of\nthe bottom cover nuts. Water from the plunger stuffing box probably gushed all\nover, and the brick masonry infill discussed in Sect. 2.1 would provide\nsome protection for the housings and tension rods by deflecting the water to\nthe basement. From the film sequence data (Sect. 10.7) the total leak\nrate of the hydraulic system during the locking period can be very crudely\nestimated at 100 litres (20 gallons) per minute, or the equivalent of six\npowerful home showers. Of course, the locking period would last for only two to\nthree seconds, but still some 5 litres (1 gallon) per stroke would leak from\nthe system at each stroke.<\/p>\n\n\n\n The two check valves shown in fig.1 are in fact two dual valves. Contemporary illustrations do not show these in much detail; some give the impression of a simple ‘ball-in-cone’ arrangement. The east valve body looks different from the west one: cover shape, casting surface, nuts etc., and it is less corroded. This valve has obviously been replaced (see Sect.10.9).<\/p>\n\n\n\n Both dual valves were dismantled; the\nvalves are hemispherical and mounted on stems guided in bushings above and\nbelow (see fig.3). All internals are of bronze. The covers are fitted with a\nrubbery compound about 5 mm thick, probably an early form of liquid gasket. Why\nso thick ? The flange and cover have mating grooves and ridges, suggestive of a\nthinner gasket more suitable for high pressure. The answer may lie in the way\nthe internals are kept in place. The cage with the top stem guide was pressed\ndown by a central bolt in the cover. This screwdown is an eyebolt which thus\ndoubled as a lifting eye. A locknut with a gasket washer secured the\nadjustment. This gasket could not, however, prevent water entering the thread\ngap from inside. Any further adjustment soon became impossible. Maintenance\nwork may have altered the position of the top guide (e.g. renewal of seat);\nmaybe the thick gasket simply bridged an adjustment gap which the bolt could no\nlonger manage.<\/p>\n\n\n\n For\nhydraulic drive these valves are not needed, and for water-hydraulics they\nshould be permanently closed. Minor leakage would seem acceptable, but even\nthat could be avoided by fixing the valves to their seats with some\neasy-to-remove glue or liquid gasket compound. The seating surfaces of three of\nthe valves and of all four seats are in good condition; there is evidence of\nrepeated grinding and occasional trueing up. The seating surface of the fourth\n(northwest) valve is severely pitted. It is difficult to say if this is due to\ncorrosion or to cavitation. It is surprising that the corresponding seat is\nperfectly smooth. After careful cleaning the pitted surface was filled with\nepoxy. This would not be suitable for normal operation, but it will hopefully\ndo for a static seal.<\/p>\n\n\n\n The\nvalve seats have an external rim to position the upper stem guide cage (see\nfig.3). There is thus a channel around the seat which, after the cleaning\noperation, held some water. After a few days the water had to be cleared out of\nthree of the channels; the SW one was dry, so the fit of the seat in the\nhousing had to be leaky. After careful cleaning, this was treated with a thin\nLoctite which would hopefully penetrate the (invisible and obviously narrow)\ngap. The channel will now hold water. The NW valve developed similar problems\nwhen the pressure was first raised to 40 bar, probably as rust and dirt were\nblown from an existing crack. The same remedy was applied.<\/p>\n\n\n\n The\nsouthwest housing has a crack in the gasket seating surface, which would\nprobably cause leakage (and would have done so in the past); this was also\ntreated with Loctite.<\/p>\n\n\n\n Surprisingly,\nthe southwest cage ring had to be enlarged slightly (by filing) to fit around\nthe corresponding valve seat. This cannot have been caused by corrosion, and\nexchanging the northwest and southwest cages only made matters worse. No\nexplanation has been found.<\/p>\n\n\n\n The\nvalves have now been re-assembled with elastic plugs (made of reinforced rubber\nhose) between valve stem top and guide end, and between guide cage and cover;\nthese will not keep the valve shut against pressure, but they will assist the\nassembly process, at least while the liquid gasket is setting.<\/p>\n\n\n\n This\nis a valve assembly in two parts. The upper part of the housing connects the\ntwo branches of the HP connecting pipe and contains the bypass valve. To this\nis flanged the lower part which connects the LP branches, and contains the\nbutterfly governor valve. The bottom is a flat cover bolted to a flange; at the\ncenter of this cover is a hole, surrounded by four screwed-in studs and\nvestiges of a gasket. As this is the lowest point of the hydraulic, this was\nprobably the drain connection. The drain cock (no doubt discharging into the\nbasement, see Sect. 2.1) is gone, probably removed when – some time\nafter 1933 – rainpipes were arranged to discharge into the standpipes. As a\nresult, rainwater from the roof, rich in oxygen and lately in acid, flowed via\nthe LP pipes of the hydraulic into the basement and thence via the\noverflow hole in the wall to the polder outside. This detour has been\nrectified, the rainpipes now run directly outside.<\/p>\n\n\n\n The\nsingle-seat bypass valve is balanced by a plunger. The double-lip rubber ring\nbetween this plunger and the sleeve lining the housing, is the only sliding\nseal in this valve being subjected to the HP-LP pressure differential. The\nremains of this seal, which had certainly been replaced a number of times\n(lastly in May 1930, viz.[2]), were deformed, had worked down into the\ngap, and then deteriorated and hardened. An ordinary rubber gasket ring lay on\ntop of it, probably to fill the space in the chamber. This seal was probably\nthe main cause of the great difficulties experienced in disassembling. It is\nnot known if this is the original form of seal. In 1849 such a seal would often\nbe made of leather. However, there is some indication that this one may\noriginally have been a stuffing box: there is no supporting ring (which would\nhave prevented a lip seal working down into the gap), the compensating plunger\nshows considerable wear, and the main hydraulic plungers also have plain\nstuffing boxes (see Sect. 3.1).<\/p>\n\n\n\n For\nwater hydraulic drive with pressurized connecting pipes, this valve should be\nsecured in the closed position. While some leakage would be acceptable,\ninadvertently opening the valve could send the weight crashing down. Preventing\nthis is essential, and any measures taken should be proof against accidental\ntampering. The operating lever has been disengaged from the stem, and a short\nlength of pipe has been fitted over the stem between the top guide and the\nlever engagement section. As with the check valves, ‘glueing’ the valve to its\nseat (reversibly, of course) was resorted to; the lip seal was replaced\nby soft packing, probably adequate as a static seal. No cover gasket or stem\npacking were fitted, as the LP space will remain atmospheric and (in principle)\ndry. If the HP connecting pipe is not used (and is sealed off at the check\nvalves) no functional restoration of the bypass valve will be needed. Note:\nthe eventual decision to use oil hydraulics has made these provisions\nredundant. <\/em><\/p>\n\n\n\n The\nbutterfly governor valve probably served only to provide better pump stroke\nspeed control during the initial stages of the drainage, when even the minimum\nweight was too large for the low (initially even zero) lift, and the\nequilibrium pipe governor alone was insufficient (see Sect.10). It was\nprobably left open permanently afterwards, and the control rod and weight were\nremoved. The weight was found in the basement. The spindle, its stuffing box,\ngland and bolts are all heavily corroded.<\/p>\n\n\n\n In\nprinciple, closing this valve would be an extra safeguard, but it would mean\nrenewing the entire spindle and stuffing box structure, preferably in situ.\nThis does not seem to be really necessary.<\/p>\n\n\n\n The\nstandpipes appear to be in good order, and only need cleaning to be suitable\n(if needed) for their original purpose. The cisterns at the top are constructed\nof 5 mm plate, and bolted\/gasketed to the top flanges of the standpipes in an\nextremely eccentric position, dictated by the structure of the building. The\neast one is riveted, the west one (renewed in 1924 [2]) is welded. The\nbottom and the lower 20 cm of the sides are badly corroded with big holes, but\nthe remainder of the plates are in good condition. During a normal engine\nstroke the cistern level would fluctuate about 15 cm, so the corroded part is\nobviously the ‘wind-and-water’ portion. But for the poor accessibility, repair\nwith e.g. reinforced plastic patches would be fairly straight\u00adforward. For\nsafety reasons, the cisterns are now secured to nearby wooden beams.<\/p>\n\n\n\n The two principal pipes (HP and LP connection between the check valves\/standpipes) are U-shaped. Internal pressure would tend to straighten such a pipe. To prevent this, the check valve housings have substantial radial supports to the engine house outer wall. The east one also has an axial support.<\/p>\n\n\n\n The LP pipe segments are joined with\nregular bolted flanges, probably fitted with flat gaskets. The HP pipe joints\nare, as far as could be made out, of the ‘spigot in socket’ type. The mating\nends each have four hefty ‘lobes’ with square boltholes in lieu of a continuous\nflange. Each pair of lobes is drawn together by a square bolt with cotters at\nboth ends. There would be gasket material between the spigot and socket\n(fig.4a).<\/p>\n\n\n\n One\nof the lobes on the first segment west of the bypass valve is broken. Repairs\nwere made (at an unknown date) as follows:<\/p>\n\n\n\n This\njoint exhibited serious leakage during the first attempts at hydrostatic\ntesting (see Sect.3.6 below). As a provisional measure, Loctite and\npolyester were applied, but if the HP connecting pipe is to be pressurized,\nmore permanent repairs will have to be made.<\/p>\n\n\n\n First\nattempts at hydrostatic testing revealed the flange leak discussed above, and\nthe new plunger packing showed some leakage as well, which could be reduced –\nbut not completely suppressed – by tightening. A pressure of about 40 bar (550\npsi) has been attained. For parts to be subject to pressure, tightness will\nhave to be confirmed at 50-80 bar (700-1100 psi) for water hydraulics\noperation.<\/p>\n\n\n\n For\nprovisional filling, a hose will be connected to one of the deaeration cocks on\nthe plunger housings. Eventually a more permanent fill\/drain connection with\nassociated valves and piping (to water supply and to outside) will have to be\nmade to a low point of the HP portion of the water hydraulic system.<\/p>\n\n\n\n One\nrespect in which the proposed active hydraulic drive will differ from the\noriginal steam drive is, that a single central – albeit distributed – upward\nforce is replaced by two concentrated forces applied symmetrically with respect\nto the center. This might conceivably cause binding. Vertical guidance is\nprovided by the following :<\/p>\n\n\n\n The\nvarious guides are spaced widely apart, both horizontally and vertically, so\nbinding is not expected to become a problem.<\/p>\n\n\n\n Additional\nnote 1996. When the mineral hydraulics system was planned, the risk of binding\nwas looked into again. It was found that skewing would have to be limited to a\nfew mm, and that positive synchronizing of the motion of the weight cap ears\nwill be needed as a further safeguard.<\/em><\/p>\n\n\n\n The\nspace above the pistons is accessible via four manholes in the cover (two for\nthe central cylinder, two for the annular one). These are rather badly aligned\nwith the corresponding openings in the false cover. For convenient removal of\nthe manhole covers, and for easy access (particularly to the HP cylinder) the\n1000 kg false cover should be lifted. This turned out to be relatively easy,\nbut replacing it requires accurate positioning. In the early days the false\ncover would probably be tied to the weight, which was then lifted by steam.\nReplacing it would require inching down the hydraulic. This is a cumbersome\nmethod, considering that even now \u2013 with three chain hoists \u2013 accurate setting\ndown remains a trial and error procedure. The false cover shows signs of\nserious damage and repairs, see Sect. 10.9.<\/p>\n\n\n\n The\nstroke between the stops is about 3 m (10 ft), the top clearance between piston\nand cylinder cover is appr. 20 cm, one may assume the bottom clearance to be\nsimilar, or maybe a bit less.<\/p>\n\n\n\n The\nindoor weight surplus was \u2013 acc. to one common interpretation of Simons [4],\nbut see Sect.10.5 and below \u2013 assumed to\nbe about 85 tons, producing a gravitational force of abt. 850 kN to drive the\npumps. For a first attempt at raising this weight the beam apertures in the\nwindows were cleared (see Sect.7), the outdoor water pumps were\ninspected and their pistons freed (see Sect.8), one hydraulic ram\npacking was removed (see Sect.3.1), and most guides were soaked with\nparaffin and oil.<\/p>\n\n\n\n Eight\nhydraulic jacks of 200 kN each were installed under the weight ears using a\nspecially designed modular support structure. The maximum upward force of\n1600 kN did, at the first attempt, not produce any motion at all. After\nremoval of the piston packing (see Sect.4.2), motion started at 1200 kN.\nA considerable fraction of this was obviously due to friction and initial\nsticking. Experiments with alternately lowering and raising the weight a few cm\nthen appeared to indicate a net weight surplus of about 70-80 tons or 700-800\nkN.<\/p>\n\n\n\n The\npiston was eventually raised about 153 cm, that is to slightly above its normal\nlimit.<\/p>\n\n\n\n After\nseveral inspection and maintenance\/repair activities (including the flame\nspraying of the plungers reported in Sect.3.2) the piston was lowered to\nabout 90 cm from the lower limit stop. This left enough working clearance above\nthe cylinder cover. Besides, the jacking arrangement will not allow further\nlowering. Only after the hydraulic cylinders had been fitted early in 1998, the\nweight could be lowered to its bottom position. Up-and-down experiments now\nappeared to indicate a net weight force of about 600 kN. In view of what has\nbeen noted in Sect.10.6 this was originally thought to be surprisingly\nlow. Re-reading Simons [4], and some further thought and discussions, resulted\nin the more likely figure of c.600-650 kN for recent times.<\/p>\n\n\n\n In\norder to keep the center of gravity low, the pistons are designed as hollow\nbodies, to be loaded with part of the unbalance weight. Simons wrote in [4]\n\u2013 published in 1848, i.e. before Cruquius was ready \u2013 that Cruquius and Lynden\nwere to have more piston load than Leeghwater. Cruquius’ supervisor, writing to\nhis superior in 1858 [9], seems so take Simons’ word for it. Probably\nnobody ever bothered to look. In view of the plans for decreasing the load, it\nis obviously important to know how much weight is present.<\/p>\n\n\n\n Several\npiston covers were lifted. Some of the fixing bolts came out in one piece. Many\neventually sheared off, badly necked by corrosion. The piston is indeed loaded\nto capacity; most of the space is filled with (evidently purpose-made) iron\nblocks of varying sizes, weighing 30 to 70 kg each. Each block has holes for\nlifting with hammerhead bolts. Grease and water have penetrated the\ncompartments of the annular piston, and fill most of the remaining space. In\nthe central piston (which was much hotter) there is little grease, no water,\nbut a lot of rust. Quantity and removal of this weight are discussed in Sect.6.2.<\/p>\n\n\n\n The\ncontract drawing of the pistons shows two diametrically opposed manholes in the\nannular piston, providing access to the space below. This location is not very\nconvenient, as these manholes would be hidden under the piston’s top cover, and\nburied under weight blocks. Both have been uncovered, but repeated attempts at\nlifting – with up to 20 kN force – failed. Probably the gap between the\ncover’s bottom rim and the hole is filled with tightly compressed rust. No\nmanhole is indicated in the central piston; maybe access to the space under it\nis via the equilibrium duct (after removing the valve, of course). These\nengines were certainly not designed with convenient maintenance in mind.<\/p>\n\n\n\n The\ntotal packed piston circumference is about 25 m. With c. 400 mm packing contact\nheight the contact surface area would be about 10 m2<\/sup>. This might well cause\nsufficient friction or sticking to explain the problems reported in Sect.\n4.1, as a very modest contact shear stress of about 0,1 N\/mm2<\/sup> would suffice to\ngenerate 1000 kN friction force. It was decided to attempt removal of the\npacking. This packing is described in [4] as of the usual type,<\/em>\nwhich would be plaited junk (hemp), compressed by a junk ring. The plates in [4]\nshow a section through the pistons for both Leeghwater and Cruquius\/Lynden, but\nthe six packing arrangements depicted are all different and some look unlikely\n(this turned out to be an artist’s interpretation of the contract drawings\nmentioned in the preface). Pole [10] does not discuss piston packing at\nlength, his plates show just a fairly deep chamber with the bottom sloping down\ntoward the cylinder wall, evidently to be filled with junk only. Later (after\nconsiderable progress had been made with packing removal) the following\nstatement was found in [11] : ‘The internal and external packings of\nthe pistons consist of hard cast iron segments at bottom, with gasket above,\npressed down by glands, also in segments’<\/em>. This segmented bottom ring,\ntriangular in shape, 100 mm deep and 25 mm wide, had indeed been found at the\nbottom of the appr. 415 mm deep and 50 mm wide chamber. K.Brown expressed the\nopinion [12] that the purpose of these rings was to assist in keeping\nthe piston central in the bore during packing renewal. Correct alignment is\nimportant to keep the piston from rubbing against the cylinder wall. Once good\nalignment has been achieved by carefully positioning the initial narrow coils\nof hemp behind the segmented ring, the remainder of the task would be easier.\nAnother effect of these segments would be to prevent the packing material from\nworking down into the gap.<\/p>\n\n\n\n Still\nlater, the contract drawing of the piston was found to show the packing chamber\nof the central HP piston as described above. For the annular piston, however, a\nsecond inverted metal ring is shown under a flat<\/em> junk ring. This would\nmuch reduce the wear surface of the packing, which would to a large extent\nserve as an ‘elastic’ cushion behind the segmented rings. This top ring was\nobviously removed later (and the junk ring given a sloping underside), perhaps\nas packing materials evolved.<\/p>\n\n\n\n Fig. 5 gives a general idea of the packing arrangement. The chamber is 50 mm wide and about 415 mm deep. The junk ring is held and tightened by nuts on hammerhead bolts (c.265 mm long,1-1\/4″ thread) fitted in recesses in the chamber wall. Total piston depth has been measured (by inserting a wire hook down the gap between piston and wall) to be about 665 mm. At the inner circumference of the annular piston there is a 130 mm deep recess so that the piston in its lowest position clears the flange with which the HP\/LP separating wall is bolted to the bottom casting. The depth of the piston edge below the packing chamber is thus 120 mm (LP inner) or 250 mm (others). The contract drawings have confirmed this. <\/p>\n\n\n\n The\ngeneral procedure was to completely remove the junk by ‘digging’ it out with a\nvariety of chisels, crowbars etc., then loosen and lift out the bottom ring,\nand finally to clear the gap below the chamber by passing a sawblade through\nit. The following observations were made for the individual packing chambers:<\/p>\n\n\n\n l Outer chamber of\nannular piston.<\/strong> The junk ring consists of five segments and could be\nfairly easily removed (both this and the wear on the bolts confirmed, that\nmaintenance was quite frequent here). Much variation in gasket type was found:\nnear the top, square sinnet was most common, with a rubber core in one layer\n(an experiment ?). Further down, the gasket consisted mostly of flat sinnet,\nmuch of it badly worn (on the outside, of course) so that it had been reduced\nto short strands. Behind the bottom ring little or no wear would occur, but\nhere the junk had deteriorated to a rather amorphous and only vaguely fibrous\nmass which was tightly compressed, and very difficult to remove. The cast iron bottom\nring consists of 7 segments, each 1,5 m long, with joints at an angle. As the\ntotal length of this chamber is 11 m, a section of about 0,5 m is not covered.\nHere the junk had been most difficult to remove. Most of the segments were\nstuck to the cylinder wall and it took a lot of prying to dislodge them. The\npiston.cylinder gap below the chamber is narrow; the sawblade could only be\npassed with difficulty.<\/p>\n\n\n\n l Inner chamber of\nannular piston.<\/strong> The junk ring is in one piece. Down to the bottom\nring all layers were square sinnet in relatively good condition, suggesting\nthat at some time this packing had been replaced in its entirety. An entry in [2]\nconfirmed this: renewed in November 1927. The space behind the bottom ring was\nfilled with a compact mass as described before. The cast iron bottom ring is in\n6 segments, and was difficult to dislodge. The gap was again very narrow, and\nin one place the sawblade could only pass after the piston had been pushed over\nslightly by driving a wedge in the packing chamber.<\/p>\n\n\n\n l Chamber of central\npiston.<\/strong>\nThe one-piece junk ring was broken, and had been repaired with iron strips\nbolted to the top. The gasket type varied, more or less as in the outermost\nchamber, and much of it was difficult to remove. Surprisingly, the two layers\nbehind the bottom ring were in fairly good condition; the narrow bottom layer\nconsisted of twisted rope instead of plaited sinnet. A few pieces of flat\nsinnet, obviously saturated with graphited grease, were solidified to a hard\nand brittle mass. This packing was, of course, exposed to fresh boiler steam.\nThis may also have been a reason to make the bottom ring of bronze, and to fit\nit quite accurately. There is no appreciable gap between the four segments. It\nis not known whether this bronze ring is original. The gap below the chamber is\nabout 7-10 mm wide. A sawblade was passed all around all the same, to make\ncertain the gap is open.<\/p>\n\n\n\n Bootsgezel\nwrites in [13] : The engine could work seven full days with one set\nof packings. In years past a kind of spun yarn packing boiled in tallow with\nblack lead was used of rectangular cross section of 80×80 mm <\/em>, but he gives\nno source for this statement. The size appears on the large side, and the many\ndifferent layers found would seem to indicate a practice of just adding a layer\nor two when the junk ring could not be tightened further, and to (wholly or in\npart) renew only if unavoidable. A seven day period seems more likely as a\ntightening interval than as the total life of a set of packings. Findings of\nMiddelkoop [14] and repair notes [2] confirm that packing\nmaintenance was a major activity.<\/p>\n\n\n\n The\nwrought iron rods are quite badly corroded in places, particularly the portion\nwhich is in the stuffing box when the engine is parked. Extensive and costly\nrepairs would be needed for smooth and tight running, which adds to the\nproblems of steaming. The relative ease with which the annular piston could be\npushed over (slightly) by wedges has already been mentioned. While\nreplacing the gland of the central piston slight lateral movement was also\nobserved. As the weight-plus-piston-rods structure is quite rigid, this may\nindicate slight play of the rods in their stuffing boxes. <\/p>\n\n\n\n The\nstuffing boxes have been emptied and cleaned. Most of the packing consisted of\nplaited hemp (square sinnet), but rubber cores and lead fabric wrapping was\nalso found. The bronze sleeves of the box and gland, and the bronze lantern\nring, ensure reasonable guidance. At the position of the lantern rings the\nstuffing box walls were heavily corroded, in places to a depth of 1 cm or more.<\/p>\n\n\n\n l The two air pumps <\/strong>have double-beat cast\niron discharge valves at the top, which constitute the bottoms of two hot\nwells. The valve seats are formed by rings of woodblocks. The hot wells have\noverflow ducts to a common collecting ‘box’ which in turn discharges to the\ncollar launder outside. This ‘box’ is of iron plate riveted to angles. Much of\nthe original construction is heavily corroded (the top is completely gone), and\nrepairs had been effected by lining the box with brick. After 1933 the\ndischarge duct provided convenient entry and shelter for pigeons, until the box\nwas filled with builders’ rubbish; this has now been removed. In the side wall\nof each hot well are four one-inch holes, slightly below the overflow duct\nlevel, and now plugged with wood. If open, these holes would have returned some\nof the hot condensate to the cistern (heating it up), with the duct serving as\na secondary overflow. The reasons for making (or plugging !) these holes are\nnot known.<\/p>\n\n\n\n The\nbronze piston rods are in excellent condition; their stuffing boxes in the hot\nwell bottom have been emptied. The rods and pistons are quite free to move.<\/p>\n\n\n\n The\nbuckets are really bucket-shaped, quite deep, with a bronze double beat valve\nsimilar in shape to the discharge valve, and a packing chamber with a junk ring\nat the rim. Tightening is quite difficult (lift the discharge valve, and reach\nthrough the valve opening). For replacing the packing the entire hot well would\nprobably have to be removed. The hot well fixing bolts were submerged, and are\nstuck and badly corroded. Still, [2] reports frequent renewal of (or\nadding to) these packings, as late as December 1928. The reasons for the deep\nbucket shape are not known, nor are those for making some of the submerged\nparts of bronze\/brass and others of iron.<\/p>\n\n\n\n Both\nair pumps have been overhauled (dismantled, cleaned, Molykote lubricated,\nassembled) to ensure smooth motion without pumping function This means that\ne.g. the wooden valve seatings were left as they were.<\/p>\n\n\n\n l The hot well pump<\/strong> pumps water (condensate\nplus injection water) from the east hot well to a feedwater cistern in the\nboilerhouse. Probably this pump was not part of the original design; in the\nearly years the engineer experimented with various arrangements to keep the\ncondenser cold, to recycle (or not) the condensate, etc. The present pump is\ndriven from beam #3. It draws from the east hot well via perforations just\nbelow the overflow duct level; the top row of perforations has been plugged\nwith wood.The effect of this would be that the remaining perforations are\nalways below the hot well level. This cannot have been done to prevent the\ndrawing of air, as the pump inlet is further down; maybe it would prevent dirt\nfloating in the hot well from entering and fouling the pump. The plunger has a\nwrought iron core to which a cast iron sleeve has been fitted with a nut at the\nbottom and a cotter at the top. The pump body has a long vertical crack (water\nhammer or valve blocking ?), jury-repaired with clamps, angle irons and\npacking material. The condensate pump’s stuffing box has been emptied. All\nbearings and guides have been overhauled and long-term lubricated.<\/p>\n\n\n\n l The condenser cistern<\/strong> has been inspected,\nalthough its condition is of no immediate importance to the moving of the\nengine. The cistern is constructed of cast iron plates bolted together. The two\nair pump barrels are supported by brackets cast integral with these plates. The\nbottom ends of these barrels are connected to the condenser barrel through\nducts, each with a rectangular cleaning cover at the top, which provides access\nto the condenser foot valves. The injection water is admitted from the cistern\nto the condenser jet by a system of three valves :<\/p>\n\n\n\n There\nis a thick layer of rust, dust and rubbish on the bottom but it appears that,\nif necessary, the cistern could be restored to function. Cleaning has been\nstarted (March 2001) as a non-urgent activity.<\/p>\n\n\n\n l The end stops<\/strong> for emergencies work on\nthe ears of the weight cap. These ears slide on the guide rods, and they also\ncarry the rams of the hydraulic (see Sect.3) and the air pump beams\n(earlier in this chapter). The bottom stops are contained in the pedestals (see\nSect.2.3). When it was decided in 1995 to look into the feasibility of\nlocating the add-on hydraulic cylinders here, the buffers were removed. A 19th\ncentury sketch indicated a horizontal partition at about half-height, with some\nsort of buffer elements stacked on. The first guess was, that these might\nconsist of felt and\/or leather, as rubber buffers were unknown at the time. As\nit turned out, the partition did not exist, and the buffer consisted of blocks\nof wood stacked on the cast iron bottom. There was some leather or hide\ninterposed, but too little to add appreciably to the very limited buffering\naction of the wood.<\/p>\n\n\n\n The\ntop stops, keyed to the guide rods, have not been touched, they would appear to\nbe of similar (but much lighter) construction.<\/p>\n\n\n\n The\npedestals have been emptied, and a large hole has been made in the cast iron\nbottom (and a supporting wrought iron plate under it) to accommodate a\nhydraulic cylinder.<\/p>\n\n\n\n l The park props<\/strong> supported the\nweight\/crosshead in the half-stroke position during long idle periods. They\nwere 1,5 m long oak timbers, 20 x 30 cm with iron bands at the ends.\nThe original props were inspected and judged unreliable (some woodworm). They\nare also unwieldy (80 kg) so, with the possible need for more frequent\nhandling, a lighter alternative was sought. The load per prop would be about\nhalf the indoor overweight or about 320 kN (or less, as some weight\nobservations seem to indicate), assume conservatively about 500 kN.<\/p>\n\n\n\n Mild\nsteel pipe c.200×4,5 mm would weigh in at 33 kg, high-strength steel\nc.200×2,5 mm would be 18 kg, aluminium c.200×4,5 mm is 12 kg. For\nbuckling, the lower specific weight of aluminium would be more than offset by\nits also much lower modulus of elasticity \u2013 but buckling is not the determining\nfactor, as the following summary shows.<\/p>\n\n\n\n Data:\nlength l <\/em>=1500 mm, diameter D <\/em>=200 mm, compressive load F <\/em>=500 000 N<\/p>\n\n\n\n Aluminium\npipes with welded end plates have been installed. For still more handling\nconvenience, handles might be clamped on (no welding !!) in a suitable\nlocation. If desired, a mockup wood casing might be made, adding about 10 kg to\nthe weight.<\/p>\n\n\n\n Note:\nthe decision to put the add-on hydraulic cylinders inside the pedestals\nnecessitates a new solution for parking support. The props described had to be\ndiscarded. Following are the calculations for an alternative.<\/em><\/p>\n\n\n\n Consider\ntwo props, each consisting of two aluminium channels 160x80x10 mm clamped\naround one of two diagonally opposed guide rods (to center the support). Weight\nc.12 kg per channel. <\/p>\n\n\n\n Data:\nlength l <\/em>=1500 mm, diameter D <\/em>=200 mm, compressive load F <\/em>=500 000 N,\nassume that (due to uneven support surface) load is taken by a single channel.<\/p>\n\n\n\n The\ncentral weight or ‘great cap’ now consists of a hollow cylindrical open-top\nmain section with two ‘ears’ clamped and bolted on Originally the ears were\ncast integrally, what we see now is a repair (see Sect 10.9). These ears\nslide on vertical guide rods, and outer projections carry the hydraulic rams\n(see Sect.1 and Sect.3.1). The central section is divided into\nsix compartments which can be loaded with purpose-made cast iron weights,\nclamped to prevent rattling etc. In four of these compartments, openings are\nleft for the beam connecting rods which extend down to bearing blocks fitted to\nthe underside of the weight and covered by two conspicuous copper pans which\nprovided oil-bath lubrication. The remaining two compartments have loose plate\ncovers. In later times scrap etc. has been added to the weight in all\ncompartments.<\/p>\n\n\n\n An\nindoor weight surplus is essential for the operation of this type of single\nacting nonrotative engine, and remains so for hydraulic drive. This surplus\nmust be sufficient to overcome friction etc. and \u2013 should it be decided to\noperate one or more of the outdoor water pumps \u2013 to provide the required lift.<\/p>\n\n\n\n The\nnet lifting force needed for one pump is about 120 kN (see Sect.10.5).\nShould it be desired to restore one pair of pumps to operation, then the\nrequired force will be 250-350 kN, to be provided entirely by the weight.<\/p>\n\n\n\n The\ntotal unbalance force of the engine (when still working) is not known\naccurately, but has been estimated at 600-650 kN (see Sect.4.2). A reduction\n(by removing weight) of 250-350 kN is thus desirable. This will change the\ntotal equivalent moving mass of roughly 250 tons by only a few per cent.<\/p>\n\n\n\n The\nrelatively large reduction of the unbalance force plus the relatively small\nchange in moving mass will result in more sluggish dynamic behaviour but, as\nthe stroke rate will be reduced, this does not seem objectionable.<\/p>\n\n\n\n In\nthe course of 1990, 8440 kg weight was removed from the weight cap which\nis now empty. Another 13555 kg was then removed from the pistons. This is\na much slower, more arduous and messier job, completed early 1997. In the\nannular piston (7985 kg) the blocks are embedded in a goo of old,\nhalf-decomposed grease and water, from which they can fairly easily be extracted.\nThe blocks in the central piston (5570 kg) are \u2018cemented\u2019 in tightly\ncompressed rust, and removing a block appeared only possible if the rust could\nbe removed first. Various methods were tried in the early 1990s, from drilling\nand grinding to a hot mixture of strong acids (Blekkenhorst), all to no avail.\nIn 1996 Harry Kruk devised a brute-force method using the more powerful tools\nthen at our disposal, which proved effective. If we allow c.200 kg for grease,\nwater etc., the grand total of removed weight is c.22.2 t, leaving\nc.40 t (400 kN) structural indoor overweight.<\/p>\n\n\n\n The\nconnecting rods and their bearings for the connection rods were dismantled and\nall bearings cleaned, overhauled and refitted with longlife grease. The bottom\nbearings, having been immersed in an oil bath and oscillating only slightly,\nwere in excellent condition, covered in a layer of hardened oil which could be\nchipped off.<\/p>\n\n\n\n There are eight main beams or \u201cbobs\u201d, one of which had been disconnected, but has since been reconnected (see Sect.10.5). The beams are of cast iron flanged latticed ‘hollowwork’ design, 2 x 5 m (equal beam). The trunnion bearings rest on cast iron soleplates. Their centres are about 60 cm inside the windows, so the top and bottom gaps between beam flanges and window aperture vary during the stroke. In addition, there are substantial side gaps between the beam flanges. This was probably found objectionable (draught, birds), and wooden boxes were fitted to the beams to obtain a constant narrow gap as shown diagrammatically in fig. 6. Such a box is also found on the single disconnected beam, so these boxes were probably fitted early on, maybe already in the building stage. They are not shown in contemporary illustrations, however. Such boxes, of varying design for different beam types, were not uncommon in Cornwall. Occasionally, one finds plain boards, which seal the aperture in a single (parking) position only.<\/p>\n\n\n\n The outdoor portions of these boxes (which\nwould have been the worse for exposure anyway) were cut off after 1933, and the\ngaps were sealed with slats. These have now been sawn through from the inside\nwith a compass saw, re-establishing a gap.<\/p>\n\n\n\n For\nregular motion over the full stroke more permanent provisions are rquired – in\n1996 work started on replacement boxes in red cedar wood (structure similar to\npine, but much more durable). By summer 2002, six boxes were complete,\nwith work on the remaining two progressing well.<\/p>\n\n\n\n The\nair pumps are driven by two additional (half-)beams. These are also of lattice\ndesign, but one has a solid central portion. This one was renewed in 1851 (see Sect.10.9).<\/p>\n\n\n\n All\nindoor and outdoor beam end bearings have been dismantled, repaired, long-term\nlubricated and re-assembled. The outdoor (nose) bearings have been fitted with\ngrease nipples. All beam trunnion bearings have been cleaned and long-term\ngreased.<\/p>\n\n\n\n The plan sketch fig.7 shows the arrangement of the pumps and the numbering convention of [2], which has been adopted for this report.<\/p>\n\n\n\n Fig.8 shows the 1847 drawing of one Cruquius pump from [11]; this differs slightly from the oldest known drawing (1846), and also from today\u2019s situation, after a replacement and numerous repairs. <\/p>\n\n\n\n Each\npump barrel is flange-mounted onto a c.1,5 m tall lantern piece B<\/em>.\nThis lantern piece has six openings f<\/em> (hence the name) which admit water\nto the pump\u2019s foot valve. It also has six external feet, which are bolted to\nthe timber floor or to the grating beams (see Sect.2.1). As the lantern\npiece is thus firmly affixed to the pile foundation structure, it can to a\nlimited but sufficient degree absorb upward forces (friction, valve dynamics,\netc.). The piston or bucket C<\/em> is an open frame built up of cast iron and\nwrought iron pieces, including extra weight d<\/em> to speed up the descent of\nthe bucket. The assembly was originally guided by two rods e<\/em> and by four\ngunmetal facings on the knee-pieces b<\/em>. The bottom ends of the guide rods\nwere used to bolt the foot valve frame and hinge supports to the seat in the\nlantern piece, their top ends are affixed to brackets bolted to the pump\nflange. Where the cast-in boltholes in that flange would not properly line up,\nextra holes were drilled \u2013 these can still be seen on some pumps. The piston\nwas suspended from the beam end by a rod and a length of patent chain. At an\nunknown date later in the 19th century, the pistons \u2013 probably the worse for\nwear and tear \u2013 were replaced with a design which is only slightly different.\nThey were now suspended from a plate link chain, which would prevent turning of\nthe piston to a sufficient degree, obviating the need for the guide rods, which were removed. The\nnew chains enforced a specific piston orientation, i.e. piston valve hinge line\nin plane of beam, that is \u201cradial\u201d. As a consequence, the foot valve hinge line\nwould also have to be radial. This meant that in many (maybe all) pumps the\noriginal foot valve fixing brackets could no longer be used. In pumps 2 and 6 \u2013\nand probably in most other pumps \u2013 the foot valve frames are now clamped to\ntheir seating flange in the lantern piece by a cast-iron crossbar underneath. Where the old pistons\nhad (four) guide rod sleeves, the new ones were fitted wih additional gunmetal\nblocks, bringing the total number per piston to eight. Two large semicircular\nplate iron clacks c<\/em> complete the bucket. These are fitted with pine rims\nto minimize the gap between piston and barrel, and with a strip of leather on\ntop of this, to make them tight. The wooden rims and leathers are held in place\nwith bolted-on plate iron glands which also provide extra weight to aid valve\nclosure. An earlier drawing shows extra weight blocks on the clacks, but by\n1847 these were gone; maybe the clack plate thickness was increased instead.<\/p>\n\n\n\n The foot valve D<\/em> is a simpler casting, again with two semicircular clacks, sealing on rims of beechwood blocks with lignum vitae bottom wedges, rammed into grooves (fig.9). <\/p>\n\n\n\n All pumps have been inspected. Pump 7 was disconnected\n(see Sect.10.5). There is evidence of many repairs to the barrels, the\nframes and the clacks. The bores of several pump barrels show areas with chisel\ndressing marks, mostly near the top flange. This may be the result of removing\ncasting flaws, and indicates that the pump barrels were never bored or\notherwise machined. The bucket chains are of varying length, probably adjusted\nindividually so that the leather strip will clear these rather rough dressed\nareas. A wear \u201cstep\u201d in each barrel \u2013 discernible in skimming light \u2013 marks the\ntop position of the bucket. Pump rod 5 has a socket-and-cotter repair at the\ntop.<\/p>\n\n\n\n Initially,\nall bucket clacks were opened a few cm and secured in that position. For pumps\n1, 3, 4, 5, 6 and 8 the buckets have been found to be quite free to move. For\npump 2 this was not ascertained initially due to lack of time. In keeping with\nMurphy’s law, this one turned out later to be firmly stuck (and very difficult\nto free) during the raising of the weight (see Sect.4.1). One of the\nwedges used for prying open the clacks, had inadvertently been left in place,\nresulting in some problems and in erroneous weight readings when the indoor\nweight was lowered.<\/p>\n\n\n\n At the start of the hydraulic project\nc.1995 it was decided to operate two diametrically opposed pumps (Nrs.2 and 6),\nand to have the other pumps run idle with open bucket valves. The final\ndecision whether or not to reconnect pump 7 was postponed, but as some of the\nother pump connections had to be disassembled anyway, one set of parts was\ncopied to be available for pump 7. The pump was eventually reconnected (see Sect.10.5).<\/p>\n\n\n\n For\nthe two operating pumps, an attempt was made to lift the foot valves\nout, for cleanup and repair, as used to be done quite regularly during\nCruquius\u2019 operating life. For pump 6 this worked (with difficulty); the\nvalve frame showed substantial repairs. The remains of the old valve seal were\nremoved from the grooves, and new blocks (crosscut beech, with lignum vitae\nbottom wedges) inserted.<\/p>\n\n\n\n Foot\nvalve No.2 turned out to be more stubborn. Its frame is sitting askew, with all\nnooks and crannies at the circumference filled solid with (expanded) rust, or\nwith tar, red lead, dirt etc. All attempts at moving this frame failed.\nCleaning and repair had to be done in situ, in rather cramped conditions.<\/p>\n\n\n\n The\nsealing surfaces (both clack surface and wood blocks) were carefully dressed.\nUnexpectedly, the seal turned out to be less than perfect, may be due to the\nsomewhat unfavourable slotted hinge arrangement. Improvements to this\n(suggested by an early drawing!) would be fairly easy for pump 6, but well-nigh\nimpossible for pump 2.<\/p>\n\n\n\n For\nall pumps the heavily rusted bucket chains were dismantled and the buckets\nlifted out for cleaning. Extensive cleaning and repairs \u2013 mainly for buckets 2\nand 6 \u2013 have\nbeen effected\nby an outside firm (Messrs.Blom). Particular attention was needed for the\ngunmetal guides, some of which were badly worn or missing. Replacements are\nvolunteer-made.<\/p>\n\n\n\n The\nwood rims on the clacks were replaced in Russian larch. The flexible seal\npresented some problems. The remains of the old leather strips were diagnosed\nby an expert to be heavy-quality (4-5 mm) cowhide. Upon his advice the\nsame leather was used on pump No.6, soaked in water to soften before shaping in\nplace, and then treated with oil (ordinary mineral engine oil). Pump No.2 was\nexperimentally fitted with 3 mm polyurethane (Vulkollan) strips. Neither\nwas a success. The leather swelled, became very soft, and in places it worked\ninto the narrow gap between wood rim and barrel. The Vulkollan did not swell,\nbut due to its flexibility it also worked into the gap. After a few weeks both\nwere replaced by a heavier (5 mm) Vulkollan which performs reasonably\nwell.<\/p>\n\n\n\n The\npiston clack seals have inherent weaknesses: The semicircular circumference of\neach clack has two cutouts for the vertical frame members carrying the guide\nshoes, and the seal has to negotiate these. At the clack hinges special seal\nflaps have to be provided. All this produces corners which inevitably leak.<\/p>\n\n\n\n If\ntwo pumps are to operate, these will need an unimpeded water supply. Inspection\nrevealed, that the foundation floor is covered with a thick (1 \u2013 1,4 m)\nlayer of rather dense mud, mixed with tree branches, decayed timbers, and other\nrubbish, effectively blocking any flow to the foot valves. Complete removal of\nthis layer is not feasible (it would entail extensive dredging in the supply\nchannel). It was decided to build two segmented cylindrical steel shells\nto stand on the foundation floor around pumps 2 and 6, allowing cleaning inside.\nHoles are provided in these\nshells, at suitable locations to admit water, but preventing both floating and\nsunken rubbish to enter the lantern pieces. The shells have sacrificial-anode\ncathodic protection. Assembling and erecting these shells, from a\nwobbly working raft, turned out to be a major task. As they would have to be\npumped out, at least partially, for cleaning and foot valve work, it was\nessential that leakage at the bottom end should be limited. The grating beam\nridges (see Sect.2.1) would be a problem here. This was overcome by\nlaying down (using a pipe funnel) a ridge of concrete along the bottom edge.<\/p>\n\n\n\n Priming\nof the pumps can no longer be done in the old way (see Sect.2.4). Due to\nthe considerable leakage, however, substantial priming facilities are required.\nAfter a number of experiments (mostly failing through insufficient capacity),\nPiet van Putten designed and made two siphons of 125 and 160 mm dia., with\nvalves for starting (with a small priming pump) and stopping (vacuum breaker).\nThese turn out to be just adequate as a bootstrap for the initial two or three\npump strokes, which then complete the filling of the barrel.<\/p>\n\n\n\n Why\ncannot a suitable connection to the canal outside be made for this\npurpose ? That would be a closer approximation to the old method. This\nwould require a substantial pipe from the canal, through the dike, to the\ncollar launder. Preliminary calculations indicate a required diameter of\n300-350 mm. There would be polder safety implications. Also, the level in\nthe collar launder cannot be allowed to rise to the canal level: the renewed\ncollar launder floor is not strong enough (see Sect.2.4), and the museum\nlobby would be flooded. Still, the idea has its attractions, and may be further\ninvestigated later.<\/p>\n\n\n\n Note\non terminology:<\/em> The three valves of a Cornish engine are controlled\nvia rods\/links from three arbors<\/em> at the driver’s position. Each arbor\nhas a handle for manually closing the valve against the action of a weight; it\nis held shut by a kind of pawl called a scoggan<\/em>, with a release lever or\nscoggan catch<\/em>. The usual arrangement is, that the lower arbor controls\nthe exhaust, the middle one the equilibrium and the upper one the steam valve.\nCorrespondingly, the exhaust handle is called the bottom handle<\/em>.\nHowever, for the equilibrium handle in the middle, the name top handle<\/em>\nis often used, reminiscent of the Watt era when engines had only two arbors.\nThe steam handle at the top is called the steam horn<\/em>. This is often\nduplicated for reliability reasons (see also Sect.10.9). During\nautomatic operation the valves are closed by clamps<\/em> or slides<\/em> on\nthe plug rod<\/em>, which strike the handles. The steam slide is usually\nadjustable and quite long (to allow overtravel after cutoff).<\/p>\n\n\n\n According\nto contemporary writings (e.g. [4]) HP cutoff was originally at approx.\n50%, as would be normal for a compound Cornish engine. The present arrangement\nof the steam slide only allows much later cutoff, in the 80-90% range (see\ndiscussion in Sect.10.5). To achieve this late setting the steam slide\nfittings were evidently moved up on the plug rod. Marks on the rod still betray\nthe original position.<\/p>\n\n\n\n Steam\nhorns are always shaped to allow overtravel of the slide after the closing of\nthe steam valve. In this engine this is achieved by using very short (dual)\nhorns, which makes manually closing the steam valve quite difficult.<\/p>\n\n\n\n When\nthe weight was raised (see Sect.4.1) it was noticed that, at the setting\nas found, the steam slides touch the horns at about 70 % and that at 100 % the\nscoggan catch engages the scoggan, but the horns are still partly ‘under’ the\nslides. At 100 % the valve must obviously be shut, so obviously the links (and\npossibly the scoggan) have been adjusted to achieve this with the horns not\nfully ‘home’. As a result, any overstroking will result in compression of the\nsteam valve links. This may have caused the slight buckling which was evident\nin the vertical steam valve link.<\/p>\n\n\n\n The\nequilibrium scoggan has also been turned slightly on its arbor and rekeyed. The\neffect would be, that for most of the steam stroke the equilibrium valve is\nheld shut by the exhaust quadrant rather than by its own scoggan (which takes\nover only when the exhaust is fully shut). At the end of the pump stroke the\nequilibrium handle must be pressed fully home (well beyond the scoggan\nengagement point) to allow the exhaust to open for the next stroke. The purpose\nof this arrangement (which increases wear of the quadrants) is unclear. The\nequilibrium scoggan has been returned to its ‘original’ position and rekeyed.<\/p>\n\n\n\n The\nclamps are wood with brass sideplates and leather-covered wear surfaces. The\nleather on the steam slide extends only a short way up and the tensioning\ndevice has been removed, as for the very late setting this was all that was\nneeded. When the leather wears thin, one sideplate of each steam slide touches\nthe handle of the corresponding horn; the wear on handles and slides shows this\nto have been quite common.<\/p>\n\n\n\n The\nvalve gear has some features not often found in Cornish engines.<\/p>\n\n\n\n The\nvalve gear has been cleaned and lubricated, and now moves without difficulty.\nThe brass bearing caps have deep recesses, mostly filled with grease-storing\nmaterials such as leather, cardboard. The rather loose bearing setting desired,\nwith nuts no more than hand-tight, increases the risk of parts disappearing.\nFor this reason, distance washers have been fitted which allow the nuts to be\nfully tightened. Maybe eventually some adjusting of weights will be desirable\n(e.g. the exhaust valve opening weight, which seems excessive in the absence of\na pressure differential), but this may be postponed. For the simplest forms of\nmotion, if the valve gear has no function, the valves should be secured in\ntheir closed position. The original rod-plus-ring for securing the bottom\nhandle is still present. For the top handle (usually left free in Cornish\npractice) the original chain-plus-ring (visible in [5] fig.355) is gone,\na replacement has been fitted \u2013 in fact, this had been \u2018re-invented\u2019 before the\noriginal had been noted in the photograph !<\/p>\n\n\n\n Returning\nthe steam slide fittings to their original position might be considered.<\/p>\n\n\n\n Somewhat\nsurprisingly, the steam valve stem \u2013 which had moved before \u2013 became stuck\nduring the first raising of the weight (see Sect.4.1); this was only\nnoticed after considerable distortion of the vertical link had already\noccurred, adding to the slight buckling mentioned earlier. The link has been\nstraightened.<\/p>\n\n\n\n The\ncataracts are not essential for hydraulic operation as such; they may however\naid in making motion and control more realistic. They have been overhauled, on\nthe main cataract the plunger had to be replaced. Originally, the cataracts ran\non water. They have now been filled with light oil which makes no difference\nfunctionally, but which prevents corrosion.<\/p>\n\n\n\n The\nfollowing observations have no direct bearing on the intended operation using\nhydraulic power. They are included here, as they may lead to a better\nunderstanding of some operational aspects of the engine’s history. <\/p>\n\n\n\n HP\npiston\ndiameter \n2146 mm (84″)<\/p>\n\n\n\n LP\n(annular) piston dia. 2235 mm\n(88″) inside, 3664 mm (144″) outside.<\/p>\n\n\n\n stroke \n3048 mm (120″) between limit stops.<\/p>\n\n\n\n top\nclearance \n200 mm (8″) if at limit stop [approx.]<\/p>\n\n\n\n bottom\nclearance \nunknown<\/p>\n\n\n\n HP\npiston rod diameter 305 mm (12″)<\/p>\n\n\n\n LP\npiston rods (4) dia. 114\nmm (4.5″)<\/p>\n\n\n\n ratio\nLP\/HP piston area 2.84<\/p>\n\n\n\n stroke\nrate \n10 per minute rated, but usually 5-6 per minute.<\/p>\n\n\n\n power \nc.220 kW (300 hp), later up to 350 kW (500 hp).<\/p>\n\n\n\n boilers:<\/em><\/p>\n\n\n\n 1849\nsix Cornish, rated at 2.4 bar (34 psi), heated surface initially abt. 55 m2<\/sup>\n(600 sq.ft) each.<\/p>\n\n\n\n c.1855\nfour flametubes behind firetube replaced by single tube, heated surface reduced\nto 45 m2<\/sup> (480 sq.ft).<\/p>\n\n\n\n 1860\nfour similar boilers added; pressure rating in following years raised to 3,6\nbar (50 psi).<\/p>\n\n\n\n 1888\nreplaced by six Lancashire, rated at 4,5 bar (65 psi), heated surface 66 m2<\/sup>\n(1060 sq.ft).<\/p>\n\n\n\n eight\noutdoor water pumps (mostly seven in use):<\/em><\/p>\n\n\n\n barrel\ndiameter \n1854 mm (73″).<\/p>\n\n\n\n stroke \n3048 mm (120″).<\/p>\n\n\n\n lift \n4,5-5 m (180-200″) average.<\/p>\n\n\n\n delivery\nrate \n250 m3<\/sup>\/min (55000 gals\/min) with 7 pumps,<\/p>\n\n\n\n at 5 strokes\/minute,\nwith spillage estimated (optimistically) at 10%.<\/p>\n\n\n\n The\nrequired drainage capacity had originally been specified on the following\nbasis:<\/p>\n\n\n\n The\ntraditional measure of efficiency of the nonrotative pumping engine is the\n\u201cduty\u201d expressed as the quantity of water (in pounds) raised one foot at the\nexpense of one bushel (94 pounds) of \u201cbest Welsh steam coal\u201d. A duty of ten\nmillion corresponds to an overall efficiency of about 1 %, or a coal\nconsumption of about 8,5 kg per hp\u00b7hour.<\/p>\n\n\n\n In\nthe design contract for the Haarlemmermeer engines, the consulting engineers\nGibbs and Dean undertook to design an engine delivering 350 hp at 10 strokes\/minute\nat full lift of 5 m with a duty of at least 70 million (i.e. 7 % overall\nefficiency). This would correspond to a coal consumption of roughly 600 kg per\nhour.<\/p>\n\n\n\n [4] reports the results of\ntrials conducted in 1846 with the Leeghwater engine, which had eleven pumps\nwith the same total piston area as Cruquius’ eight. During the trials only nine\npumps were connected, and a small portion of the lake was temporarily endiked,\nforming a \u201cmini-polder\u201d, which allowed varying the lift. The trials started with\n2,7 m lift, and at 4,1 strokes\/min an efficiency of 2,4 % was obtained. For\nincreased lift the efficiency rose to a maximum of 7,1 % for 4,6 m lift and at\n5,8 strokes\/min (278 hp). When after this result the speed was raised to 6,4\nstrokes\/min, power rose to 312 hp, but efficiency dropped sharply to 4,3 %. The\nhighest speed reported is 7,5 strokes\/min. No details of steam pressure,\nweight, cutoff etc. have been found to date, so it is not known if these were\noptimized for every value of the lift.<\/p>\n\n\n\n These\nresults appear to indicate that the specifications were not fully met, and that\npronounced optimum efficiency conditions exist. Many of the changes etc.\ndiscussed below would imply a substantial reduction of efficiency. It is\ndifficult to find hard figures, and operating conditions probably varied over\nthe years. P.Boekel ([18], particularly pp202-218) lists figures mainly\nfor the early 1860s. These are far from comprehensive, and now quite difficult\nto interpret: maybe even then his source material had gaps, and he was no\nengineer. He recognizes the variability \u201deach year is different, and\nhard-and-fast calculations cannot be made\u201d<\/em>. From his data, a ball-park\nfigure of 1000 kg\/h may be estimated; this would be in fair agreement with the\nefficiency figure of c.4,5% he implies elsewhere. Not bad, considering all the\nadverse changes.<\/p>\n\n\n\n An\nimportant operating problem with non-rotative pumping engines is stroke length\ncontrol. Overstroking can result in serious damage. Understroking, while not\nimmediately damaging, degrades performance and may stop the engine if not\ncorrected by the driver. The two halves of the stroke (designated here as steam\nstroke<\/em> and pump stroke<\/em>) each require their own provisions for\ncontrol, adjustment and safety.<\/p>\n\n\n\n l The steam stroke starts when the exhaust\nand steam valves open as their scoggans are released. Steam enters the\ncylinder, its flow rate usually controlled by a throttle valve \u2013 the steam\ngovernor. At some point during the steam stroke the steam supply is cut off,\nand during the remainder of the stroke the steam expands. Gravity and falling\npressure slow down the piston, and bring it to a stop. Near the end of the\nstroke the exhaust valve closes. The volume of steam in the exhaust side\nclearance space is trapped, but this cannot do much cushioning, because of the\nlow initial pressure (i.e. an imperfect vacuum).<\/p>\n\n\n\n The\nmost important means of steam stroke length control are steam throttling (easy\nand flexible, but bad for efficiency or ‘duty’) and cutoff adjustment\n(maintains or improves duty, but is rather sensitive and requires more driver\nskill). Some of the highest-duty Cornish engines were built without a steam\ngovernor; but often a throttling device was fitted later, sacrificing duty for\nconvenience. Cutoff might range from 10-15 % to nearly 100 %, but 20-50 % would\nbe common. In some cases extreme throttling (\u201cwire drawing\u201d) was practised.\nThis is now known to be wasteful, but at the time thermodynamics was still in\nits infancy, and even experienced men like William Husband of Harvey’s (who\nsupervised the building of Cruquius) seem to have harboured the notion that\nthrottling was of similar benefit as expansion, as either reduces the pressure\nin the cylinder [15].<\/p>\n\n\n\n l The pump stroke starts with the release\nof the coupled equilibrium and hydraulic bypass valves. When these close near\nthe end of the stroke, the water in the hydraulic is trapped again, and this\nappears to be the principal agent to stop the engine \u2013 fairly abruptly. Speed\nand stroke length control is mainly by adjustment of the surplus of dead weight\nover pump load, i.e. by adjusting the weight. This conserves duty, and in a\ntraditional Cornish engine with a constant (or only very gradually varying)\npump load this adjustment is fairly convenient. When, however, more flexible\nshort term control is desired, equilibrium throttling may be resorted to at the\nexpense of duty.<\/p>\n\n\n\n On\ntraditional Cornish engines equilibrium pipe throttling is rarely found. The\nMaudslay and 100″ engines at Kew Bridge are among the few known examples.\nThe Haarlemmermeer engines all had equilibrium throttling provisions (possibly\nto avoid having to adjust the weight for lift fluctuations or when \u2013 not\ninfrequently \u2013 one or more pumps would have to be disconnected for repairs [14]).\nIn Cruquius and Lynden additional control was possible using a throttle valve\nin the hydraulic bypass connection \u2013 this appears, however, to have been seldom\nif ever used.<\/p>\n\n\n\n The\nCornish engine works most conveniently and efficiently with a constant<\/em> load<\/em>,\nimplying constant work per stroke. Power<\/em> is then easily varied by\nchanging the stroke rate \u2013 i.e. adjusting the pauses of the cataracts.<\/p>\n\n\n\n For\nan existing polder the lift (being the level difference between polder and\nreservoir) varies only slightly, and so an engine can be designed to suit this maintenance\ndrainage<\/em> task very well. During initial drainage<\/em>, however, the lift\n(and thus the load) increases gradually from zero to its final value.<\/p>\n\n\n\n Load\nvariations may be accommodated in a variety of ways.<\/p>\n\n\n\n In\nCruquius the structural fixed indoor overweight with empty pistons and weight\ntrough is about 40 tons, exerting about 400 kN. For h<\/em> m lift one pump of\n2,7 m2<\/sup> piston area exerts 27h<\/em> kN. Added to this would be\nfriction, according to [16] amounting to about 20 kN per pump. The\nstructural weight would then be sufficient to drive eight pumps at a lift of\nabout 1 m, discounting LP piston work (which would increase the figure).<\/p>\n\n\n\n Various\nsources quote different steam pressures for the initial years, and it is not\nalways clear if absolute pressure or gauge pressure (= overpressure = one bar\nless than absolute pressure) is meant. The earliest and most direct sources are\nthe Stoomwezen government inspection records, and Simons [4]. The\nStoomwezen records quote the test pressure rather than the rated operating\npressure, but the law links the two \u2013 implying a boiler rating of 2,4 bar gauge\nin 1856 (start of records). Simons quotes 3 bar absolute, i.e. 2 bar gauge \u2013\nimplying that he observed a margin relative to the rating. The rated pressure\nof 2,4 bar working on a piston area 3,6 m2<\/sup> could lift about 860 kN,\ni.e. statically raise a weight of about 86 t if no vacuum present (startup\nconditions). The weight can be raised full stroke if no cutoff applied.\nAcceleration of about 250 tons of machinery (crude estimate), and friction, would\nbe extra, so a practical limit to the weight would be lower, maybe c.65 tons.<\/p>\n\n\n\n Note\nthat the 86 t calculated above, appears strongly reminiscent of the\n85-86 t mentioned by Simons on p.8 of [4]; the significance of the\ntwo figures is, however, fundamentally different: above is computed the maximum\nweight that can<\/em> be raised with the rated<\/em> boiler pressure under\nstarting conditions (no vacuum). Simons gives (with little underpinning) the\nweight required<\/em> under operating conditions with compound action, full\nvacuum, and all pumps working at full lift. That the two figures are equal,\nwould appear to be a coincidence.<\/p>\n\n\n\n For \nthe first quarter of the initial drainage, therefore, Cruquius could operate\nwith eight pumps, and with empty weight trough and pistons. For the first few\nmonths even this minimum structural overweight was excessive, and in addition\nto pump stroke throttling (in the equilibrium pipe and also in the hydraulic\nbypass, see Sect.3.3), wooden boxes with weight blocks were hung from\nthe outdoor beam ends. HP cutoff might initially have been 40-50%, later\npossibly 70% or more (see also Sect.9)<\/p>\n\n\n\n From\nlift abt. 1 m, the pistons and weight trough could be filled and drainage could\nproceed to take the lake down about 2 m, With six pumps c.65 ton weight\nwould work up to c.3 m lift, and with four pumps the full lift of\nc.5 m could be mastered. All this is without the supplementary power of\nthe annular LP piston \u2013 which is not available during starting. After the\nengine has been started and is working regularly, that additional power will\nenable the driver to use earlier cutoff, or (wasteful, but convenient) to apply\nmore steam throttling.<\/p>\n\n\n\n This\nprocedure of trading capacity for lift during initial drainage was planned (see\ne.g. \u00a7 359\/360 of [17]) to maximize efficiency, and capacity would thus\nbeing reduced (over the initial drainage period) from nearly 1 million m3<\/sup>\/day\nto some 0,5 million m3<\/sup>\/day per pumping station at the\nrated 10 strokes\/min. For the more practical 7 strokes\/min average, final\ncapacity for three continuously working pumping stations would come to roughly\n1,5 million m3<\/sup>\/day. The volume to be pumped out during initial\ndrainage was about 800 million m3<\/sup>, thus requiring about 1,5 years,\nwith some allowance for maintenance etc. Various setbacks (mostly\nnon-technical), pushed this up to over three years.<\/p>\n\n\n\n After\ninitial drainage the volume to be pumped out annually would be about\n55 million m3<\/sup>, but rainfall is distributed very irregularly,\nso [17] \u00a7311 puts the maximum monthly discharge requirement\nconservatively at 36 million m3<\/sup>. At optimum efficiency (and number\nof pumps halved) two pumping stations could just make this. This would have\nensured discharge of the maximum one-month influx within a month \u2013 the design\nrequirement \u2013 even with one pumping station out of order.<\/p>\n\n\n\n Soon\nthis was considered to be inadequate \u2013 perhaps already before the initial\ndrainage had been completed. Evolving agricultural practices (such as\nmechanization) demanded tighter water table control, i.e. higher instantaneous\ndischarge capacity. These requirements could be met by the three pumping\nstations if more pumps could be connected at full lift. This would mean adding\nmore weight, pushing the boilers to their pressure limit, and using (much)\nlater cutoff \u2013 all playing havoc with efficiency, but this was either not\nunderstood, or maybe simply accepted (as being cheaper than adding another\npumping station). It seems likely, that the starting aspects discussed in Sect.10.6\n, together with boiler pressure limitations, eventually limited the number of\npumps to seven, thus accounting for Cruquius\u2019 permanently disconnected pump.\nFor a long time we thought, that the choice of the disconnected pump (No.7) had\nbeen fairly arbitrary, but closer inspection has revealed that pump No.7 has\nmuch more serious damage than any of the others: extensive piston repairs,\nbroken and distorted bob nose bearings, damaged beam trunnion bearings.<\/p>\n\n\n\n It\nappears unlikely that weight-change was eventually used to any appreciable\nextent for operational control purposes. The full lift force for one pump is of\nthe order 120 kN. To accommodate the (dis)connecting of a single pump by\nweight alone, about 12 tons of weight would have to be removed or added. The\nweight trough contained only about 8,5 tons (see Sect.6.2), much of\nwhich showed no signs of ever having been shifted. The weight in the pistons is\nmuch more difficult to handle, and was probably never touched either.\nThrottling appears the most likely principal means of control.<\/p>\n\n\n\n Should\npump No.7 be reconnected ? In principle this is a matter of restoration\nethics, in practice it is a rather marginal item. During restoration it turned\nout to be quite easy to have replicas made of the few missing items (bronze\nbearing halves, loop, cotters), and shortly afterwards these were fitted\nwithout much fundamental debate.<\/p>\n\n\n\n There\nare several ways to build up the condenser vacuum during starting:<\/p>\n\n\n\n In\naddition, the engine and condenser are often flushed with steam prior to\nstarting, by disabling or bypassing the exhaust-equilibrium interlock. This is\ndone in the Maudslay and 90″ engines at Kew by temporarily disconnecting\nthe equilibrium valve rod from its arbor. The rod is reconnected immediately\nprior to starting the first stroke. Although this may also expel air to some\nextent, it is mainly done to gradually warm the engine through [12].<\/p>\n\n\n\n At\nCruquius there is no evidence of special steam inlet provisions for method\u0082<\/strong>,\nand the arrangement of the valve gear makes Kew-style flushing impractical.\nOnly method \u0081<\/strong> remains. For a very\nlarge engine with 50 % HP cutoff (according to [4]) this method would\nseem feasible \u2013 if somewhat primitive \u2013 provided enough excess steam pressure\nis available to gradually increase expansion and lengthen the strokes. If the\npressure is marginal, however (as it would be with seven pumps at full lift)\nthere is probably somewhat less room for throttling, and a smooth transition from\npartial strokes at c.2 bar pressure differential, to full strokes at about 2,8\nbar will be difficult to achieve. Starting might become \u2013 and reputedly was \u2013 a\ndifficult and lengthy process.<\/p>\n\n\n\n Indicator\ndiagrams taken in 1858 show that cutoff had been delayed to 80-85%, to increase\nthe work per stroke (see Sect. 10.5). One side effect is, that after\ncutoff only a very short portion of the stroke remains to bring the piston to a\nstop. Moreover, the long admission period is liable to produce high piston velocity,\nunless considerable throttling is applied. That appears to have been done, as\nindicated by the markedly sloping admission portion of the diagrams. For very\nlate cutoff the starting procedures \u0081<\/strong> and \u0082<\/strong>\nbecome virtually the same. The short expansion portion of the stroke makes it\nvery difficult to control the starting process; this would also favour a high\ndegree of throttling.<\/p>\n\n\n\n The\ncombination of evaporative capacity of the boilers and duty of the engine sets\na limit to the total power that can be developed. Both late cutoff and\nthrottling reduce the efficiency (duty), and thus the available pumping power.\nStructural problems in the boilers (i.e. the joint of the four large flametubes\nto the end of the short firebox) were solved at the expense of a reduction of\nthe heated surface, and thus of the evaporative capacity. It is not surprising\nthat in the late 1850’s the need for more steam was felt, and an increase in\nthe number of boilers was resorted to. Pressure rating remained unchanged, and\nindicator diagrams taken ‘before and after’ show – somewhat surprisingly – that\nonly a modest increase in the work per stroke was obtained. See [16] for\nmore details.<\/p>\n\n\n\n At\nsome time between 1860 and 1870 the pressure rating of the boilers was\nincreased from 2,4 to 3,6 bar, and in 1888 Cruquius was reboilered, with\nthe new boilers rated at 4,5 bar. Even the first increase would have allowed\nstarting with the full load of eight pumps, but it appears that more throttling\nin the interest of more convenient control was opted for instead. The eighth\npump was apparently never reconnected. Of course, by this time specific Cornish\nengine knowledge in Holland would have been even less than in the youth of the\nengines, so maybe these practices \u201chappened\u201d, rather than that they were \u201copted\nfor\u201d.<\/p>\n\n\n\n Perhaps\nthe film sequence, possibly made on the occasion of the final steaming on 10th\nJune 1933, contains clues. The available video copy is obviously accelerated, possibly\nby about 50%; times mentioned below take this into account.<\/p>\n\n\n\n Several\nexterior shots show complete and uninterrupted steam strokes, which look quite\nsmooth and regular. One of these has been interpreted frame by frame to\nconstruct approximate motion diagrams. One interior shot looks down on the\nweight as it rises during the steam stroke. This is less smooth, and\n‘hesitates’ at about 3\/4 of the stroke. All steam strokes take about three\nseconds, which seems quite long. The precise stroke length cannot be derived\nfrom these sequences. There is one interior shot of the valve gear, showing\nmost or all of a steam stroke and terminating just after the (manual) release\nof the equilibrium valve.(The spoken comment suggests that this is the engine\u2019s\nfinal stroke, but the sound was added much later, so this is not conclusive).\nThe plug rod comes to a stop just before<\/em> the steam slide touches the\nhorns, i.e. with the steam valve still open.<\/em> At this moment the exhaust\nclamp has already slightly moved the bottom handle, so the slide setting\nis for cutoff at approximately 90 %, as described earlier, and the engine is\nobviously short-stroking. As a result the exhaust and \u2013 via the interlock \u2013\nsteam valves must be closed by hand. It requires two men on the exhaust handle\nto do this. The reason for this is that four<\/em> valve weights have to be\nlifted (two regular ones on the arbors, one massive extra weight on the exhaust\nvalve frame and one on the support\/interlock arbor which provides a degressive\nopening force to the steam valve). This stroke is, of course, not necessarily\ntypical; the steam slide setting, however, probably is. The \u201chesitant\u201d stroke\nmentioned earlier could result if an impending short stroke were ‘helped along’\nby quickly turning up the governor or, conceivably, by the wire-drawn steam\npressure ‘picking up’ as the piston slows down (a peculiar phenomenon, observed\nin the indicator diagram of at least one other Cornish engine \u2013 preserved at\nSandfields waterworks pumping station, S.Staffsh., England).<\/p>\n\n\n\n Careful\nscrutiny of the end of the steam stroke reveals that, during the short period\nbetween steam and pump strokes, when the weight is held by the hydraulic,\nnoticeable creep occurs. The hydraulic is obviously leaky (see also Sect.\n3.1).<\/p>\n\n\n\n This\nfilm sequence confirms that the operation of the engine was difficult and in\nsome respects even marginal.<\/p>\n\n\n\n Mr.\nA.C.Zuethoff studied engineering in Amsterdam, and he recalls a visit to\nCruquius with his steam power teacher in 1928 (from the log in [2] this\ncan only have been on Saturday, June 30, 1928). He is positive that the engine\nran without much driver action. This observation indicates regular operation,\nthe occasional twist of the steam governor may have gone unnoticed. There was a\nlot of steam in the engine room, indicating substantial leakage, probably\nmainly from piston rod and valve stem glands.<\/p>\n\n\n\n On\nthis date the most serious mishap in the history of the engine occurred. The\ninitial drainage was about two-thirds complete, and the engines were still in\nthe care of the government Commission managing the drainage project. Principal engineer\nJ.A.Beijerinck reports to the Commission that the engine ran away during the\nsteam stroke. He writes that the cause is quite evident, that the driver is\ncertainly not to blame, and that an investigation is under way \u2013 so he cannot\ngive any details now. In the following months he reports on the repairs, but he\ndoes not return to the subject of the cause. One of the few possibilities that\ncomes to mind is a breakage in the lever-and-rod train operating the steam\nvalve. Could it be that Cruquius had been fitted (like Leeghwater, also built\nby Harvey) with a single<\/em> steam slide ? In that case, breaking of the\nsteam horn would produce a runaway. This is speculation; if it is true, then\nthe present dual steam horns and slides would be retrofits. We cannot check, as\nno drawings of the original valve gear survive.<\/p>\n\n\n\n The\nresults were devastating. As Beijerinck reports, the weight cap hit the upper\nblocks at full speed, and as a result both ears broke off. The E. air pump beam\nbroke in two, and the half that had been supported by the weight ear neck came\ncrashing down, damaging the false cover of the cylinder (see Sect.4).\nBeijerinck\u2019s report gives no further details of the damage, but the sequence of\nevents can be inferred from various observations. If the beam fragment of\nperhaps two tons would have crashed directly onto the false cover, this would\nhave been smashed to bits and be beyond repair. The several large cracks\nvisible today, indicate a glancing blow at worst, with the main part of the\nbeam fragment crashing through the timber engine room floor and smashing the E.\npair of hydraulic check valves in the basement five metres further down (see Sect.\n3.2). Another glancing blow was dealt to the cast iron stairs close to the\ncheck valve, removing two steps and upsetting two more. The blow to the stops\nwas transmitted to the building by the guide rods. The cast iron columns\nbriefly lost their pre-compression and probably moved a bit; the shock may\naccount for the damage discussed in Sect. 2.3.<\/p>\n\n\n\n Over\nthe next three months repairs were carried out, and the engine resumed work in\nApril 1851. The main job was making and fitting new ears to be clamped onto the\nremaining central portion of the weight cap. These ears were designed and cast\nin Amsterdam, by Van Vlissingen & Dudok van Heel. The same firm had made\nthe beams, including the air pump half-beams, so they could make a replacement\none from the original pattern. The lattice openings in the central portion of\nthe pattern were filled in for strengthening, traces of their outlines are\nstill faintly visible in the replacement beam. Strips were riveted to the\ncracks in the false cover, a small portion \u2013 that had probably been smashed to\nbits \u2013 was replaced by a repair casting. Other repairs must again be inferred\nfrom observations. One of the damaged column feet was secured with clamps, the\nother three were left alone. A new pair of check valves was made and fitted, it\nis not known by whom. Repair of the stairs was deferred, and eventually done in\n1996 (!).<\/p>\n\n\n\n A\nnumber of measures have been taken in connection with hydraulic drive, that\nshould be reviewed and possibly undone before steaming can be considered. In\naddition several jobs have been left ‘unfinished’, as the final steps were\ncostly or time consuming, while not essential for hydraulic operation.<\/p>\n\n\n\n At\nan early stage, the idea prevailed that in the rather unlikely event of\nrestoration to steam, the hydraulic drive would also remain operational,\nallowing e.g. frequent hydraulic operation for the general public with\noccasional steam days for the enthusiasts, implying convenient and quick\nchangeover. This turned out to be impractical: steam operation would require\ndisconnecting (not removing!) the hydraulic drive.<\/p>\n\n\n\n Hydraulic\ncylinders:<\/em>\nThese will have to be disconnected – see hydraulic drive documentation.<\/p>\n\n\n\n
Summary<\/a>
Note on the Cornish engine cycle
Note on engineering reference documents
Note on the ‘state to restore to’
1. Power source
1.1 Steam
1.2 Air
1.3 Electric drive
1.4 Hydraulic drive
2. Building and engine foundations
2.1. Basement and foundations
2.2. Cylinder holding down bolts
2.3. Columns and tension rods
2.4. Collar launder
3. Hydraulic
3.1. Plungers and plunger housings
3.2. Check valves
3.3. Bypass valve and governor
3.4. Standpipes
3.5. Piping
3.6. Hydrostatic test (water hydraulics operation only)
3.7. Filling and draining (water hydraulics operation only)
3.8. Vertical guides and the risk of binding
4. Steam cylinder
4.1. Moving the piston up and down
4.2. Pistons
4.3. Piston rods
5. Miscellaneous parts
6. Weight
6.1 General discussion
6.2 Weight removal
6.3 Bearing overhaul
7. Beams
8. Outdoor pumps
9. Valve gear
10. Working life : operational aspects
10.1. Principal engine data
10.2. Design capacity
10.3. Efficiency or duty
10.4. Stroke length control
10.5. Adjusting to varying load
10.6. Starting
10.7. The film sequence
10.8. An eyewitness account
10.9. What happened on 14 January 1851?
11. Cautionary notes for future steam enthusiasts
Acknowledgements
References<\/p>\n\n\n\n
<\/p>\n\n\n\nNote on edition<\/h1>\n\n\n\n
Summary<\/h1>\n\n\n\n
Note on the Cornish engine cycle<\/h1>\n\n\n\n
Note on engineering reference documents<\/h1>\n\n\n\n
Note on the ‘state to restore to’<\/h1>\n\n\n\n
1. Power source<\/h1>\n\n\n\n
1.1 Steam<\/h2>\n\n\n\n
1.2 Air <\/h2>\n\n\n\n
1.3 Electric drive <\/h2>\n\n\n\n
1.4 Hydraulic drive<\/h2>\n\n\n\n
![\"This](\"https:\/\/cruquiusmuseum.nl\/EN\/wp-content\/uploads\/2019\/02\/image.png\")
<\/figure>\n\n\n\n2. Building and engine foundations<\/h1>\n\n\n\n
2.1.\nBasement and foundations<\/h2>\n\n\n\n
2.2. Cylinder holding down bolts<\/h2>\n\n\n\n
2.3. Columns and tension rods<\/h2>\n\n\n\n
![\"\"](\"https:\/\/cruquiusmuseum.nl\/EN\/wp-content\/uploads\/2019\/02\/image-1.png\")
<\/figure>\n\n\n\n2.4. Collar launder<\/h2>\n\n\n\n
3. Hydraulic<\/h1>\n\n\n\n
3.1. Plungers and plunger housings<\/h2>\n\n\n\n
3.2. Check valves<\/h2>\n\n\n\n
![\"\"](\"https:\/\/cruquiusmuseum.nl\/EN\/wp-content\/uploads\/2019\/02\/image-2.png\")
<\/figure>\n\n\n\n3.3. Bypass valve and governor<\/h2>\n\n\n\n
3.4. Standpipes<\/h2>\n\n\n\n
3.5. Piping<\/h2>\n\n\n\n
![\"\"](\"https:\/\/cruquiusmuseum.nl\/EN\/wp-content\/uploads\/2019\/02\/image-3.png\")
<\/figure>\n\n\n\n3.6. Hydrostatic test (water\nhydraulics operation only)<\/h2>\n\n\n\n
3.7. Filling and draining (water hydraulics operation only)<\/h2>\n\n\n\n
3.8. Vertical guides and the risk of binding<\/h2>\n\n\n\n
4. Steam cylinder<\/h1>\n\n\n\n
4.1. Moving the piston up and down<\/h2>\n\n\n\n
4.2. Pistons<\/h2>\n\n\n\n
![\"\"](\"https:\/\/cruquiusmuseum.nl\/EN\/wp-content\/uploads\/2019\/02\/image-4.png\")
<\/figure>\n\n\n\n4.3. Piston rods<\/h2>\n\n\n\n
5. Miscellaneous parts<\/h1>\n\n\n\n
6. Weight<\/h1>\n\n\n\n
6.1 General discussion<\/h2>\n\n\n\n
6.2 Weight removal<\/h2>\n\n\n\n
6.3 Bearing overhaul<\/h2>\n\n\n\n
7. Beams<\/h1>\n\n\n\n
![\"\"](\"https:\/\/cruquiusmuseum.nl\/EN\/wp-content\/uploads\/2019\/02\/image-5.png\")
<\/figure>\n\n\n\n8. Outdoor pumps<\/h1>\n\n\n\n
![\"\"](\"https:\/\/cruquiusmuseum.nl\/EN\/wp-content\/uploads\/2019\/02\/image-6.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/cruquiusmuseum.nl\/EN\/wp-content\/uploads\/2019\/02\/image-7.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/cruquiusmuseum.nl\/EN\/wp-content\/uploads\/2019\/02\/image-8.png\")
<\/figure>\n\n\n\n9. Valve gear<\/h1>\n\n\n\n
10. Working life : operational\naspects<\/h1>\n\n\n\n
10.1. Principal engine data<\/h2>\n\n\n\n
10.2. Design capacity<\/h2>\n\n\n\n
10.3. Efficiency or duty<\/h2>\n\n\n\n
10.4. Stroke length control<\/h2>\n\n\n\n
10.5. Adjusting to varying load<\/h2>\n\n\n\n
10.6. Starting<\/h2>\n\n\n\n
10.7. The film sequence<\/h2>\n\n\n\n
10.8. An eyewitness account<\/h2>\n\n\n\n
10.9. What happened on 14 January\n1851 ?<\/h2>\n\n\n\n
11. Cautionary notes for future\nsteam enthusiasts<\/h1>\n\n\n\n