192 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[Mat, 



small, for as it formed at the same time both piston and Talve, and in the 

 return stroke, from its nearly vertical position in the working barrel, the 

 parts in contact, were reduced to the area of the points of the minor axis of 

 the disc, the friction was in proportion to that area. As a seat valve, he 

 thought it less liable to become defective, than any other, as it was scarcely 

 possible for any sand, or other foreign matter to lodge upon it, and the valves 

 which he had seen at work did not show any symptoms of being so affected. 



Mr. Farcy said, that it was an axiom relative to steam engines, that their 

 action became more perfect as their size increased, but that this could not 

 apply correctly to pump valves ; for as their size had augmented, the difficul. 

 ties in their construction had been more fully developed. With small valves 

 it had been considered, that the vertical height of the lift of a clack, should 

 be one-fourth of the diameter of the barrel, but it was evident that rule 

 could not be adhered to with large valves. Other forms, allowing a free 

 passage for the water, had therefore been resorted to, and with great success, 

 but there was still room for improvement. He had a high opinion of the 

 valve, which had been used originally by Messrs. Boulton and Watt, and 

 which was called, from its form, the 'Bishop's cap,' It consisted of four 

 triangular flaps of leather, hinged on the periphery of the valve and meeting 

 in the centre ; the number of these flaps had l)een, he believed, increased to 

 six and eight for very large sizes, and they afforded a very free passage for 

 the water. Much yet remained to be done, in improving the valves of the 

 air pumps of steam engines, especially in adapting them to the speed of the 

 engine, so as to avoid the loss of power, consequent on drawing, or forcing 

 the water through contracted passages. 



Mr. Jordan was happy to find his opinion of the disc valve corroborated. He 

 had viewed it almost entirely as a clack valve, on which the whole weight of the 

 column of water would rest, and for that purpose he thought it particularly 

 suited, lie could not agree in the opinion that chips of wood or other sub- 

 stances, would be liable to accumulate near the axis, and render it leaky. 

 He thought, on the contrary, that it would clear itself very easily, and as the 

 faces or seats were vertical, it was not possible for anything to rest upon 

 them. It had been urged that these valves were difficult of construction, and 

 would scarcely be found tight, under a very heavy column. He conceived 

 however, that with modern machinery, there could not be any trouble in 

 making them perfectly accurate, and that the simple addition of a beard of 

 leather, fixed on the upper side of the longer portion of the valve, and to the 

 seating at the shorter part, would render the valves quite tight. 



Mr. Homersham observed, that any particular form and proportion of a 

 valve, which enabled it to answer well, in one situation, was no criterion of 

 its doing the same, under other circumstances ; for instance, the suction and 

 delivery valves, of the pump of a Cornish mine engine, required to be dif- 

 ferently proportioned ; as in order to follow the speed of the plunger, the 

 water was oliliged to move through the former, more rapidly than through 

 the latter ; for the velocity of the down stroke of the steam piston of a 

 Cornish engine, was chiefly regulated by the portion of the stroke at which 

 the steam was cut oft", whereas its velocity in going out, was most usually ad- 

 justed by varying the period of the pause at the end of the stroke ; although 

 it was also somewhat governed by the number of strokes per minute, which 

 were required to be made. Therefore, as the plunger always moved quicker 

 in the former, than in the latter case, the velocity of the passage of the 

 water through the suction valve (unless its area was increased), was greater 

 than through the delivery valve, and the moving part of the valve, against 

 which the water impinged, required to be heavier in the former than in the 

 latter, to insure its closing, before the return stroke of the engine com- 

 menced. This had been pointed out in his paper on valves, which was read 

 in the last session, and a rule was given '^ for their relative weights, which 

 should always be in proportion to the velocity of the water passing through 

 them ; if this were not attended to, and they were both made of the same 

 weight, the delivery valve would not open freely, and thus more weight 

 would be required to carry the engine • outside,' and the duty would be 

 diminished. He was therefore of opinion, that every valve required to be 

 adjusted expressly for the situation in which it was placed, and the duty it 

 was required to perform. 



Mr. Galloway drew the attention of the meeting, to a pump which was in- 

 troduced by Mr. Jacob Perkins in 1820, " and was rewarded by the Society 

 of Arts. 'The barrel consisted of four boards, nailed together, so that its 

 horizontal section formed a square. Tlie bucket-rod was enlarged to a broad 

 end, intersecting the square diagonally ; to this, two valves were affixed by 

 leathern hinges. Their form was that of an isosceles triangle, the base of 

 each being united to the rod, and the other sides resting, in an inclined 

 position, against the inner sides of the barrel, filling the entire area. In the 

 down stroke of the bucket, this form offered little opposition to the water, 

 and was sufficiently tight for common purposes, with but little friction. Mr. 

 Galloway subsequently constructed a pump with a wooden barrel, in which 

 the valve was in one piece ; the preponderating action, like that of the oval 



16 The following is the rule refered to by Mr. Homersham. " The mean velocity of 

 the water in feet per second through the valve being ascertained, one half more is 

 added, and considered as the ma.ximum velocity of the water through the valve, and the 

 height of the head of water being found that would produce the velocity, every 13 inches 

 of such height is then considered as equal to an ounce weight avoirdupoise acting upon 

 every square inch contained in the area of the valve, against which the water impinged in 

 its passage to the pump barrel, allowance lieing made for the ditference of the weight ot 

 the ring when immersed in water, compared with its weight in the air." 



1 7 Vide " Transactions of the Society of Arts," 1820, vol. xxxviii., p. 106. 



disc pump, was effected, by giving the barrel the form ot a trapezium, the 

 valve being suspended by an axis, which crossed it at the bases of the two 

 unequal parts. Neither the trapezium valve, nor that of Jacob Perkins, were, 

 he conceived, generally applicable ; their utility would not extend beyond 

 domestic purposes, or those countries, where the means of boring cylindrical 

 barrels were not attainable. Mr. Galloway was of opinion, that the principal 

 objections to the eUiptical disc valve were, first, that as the axis of the valve, 

 did not coincide with the minor axis of the ellipse, the spindle would either 

 benp, on the valve being raised to a vertical position, or it would not fit the 

 cylinder when it was shut; secondly, that there was no compensation for 

 abrasion, across the minor axis, so that when the valve was worn, either by 

 the friction of sand or from other causes, it would become leaky. Mr. Gal- 

 loway then exhibited a form of valve, by v\'hich he submitted these objections 

 would be obviated. If an ellipse was intersected diagonally, at an angle of 

 45° with the major and minor axes, and one portion was turned over, so as 

 to produce a heart-sbaped figure, when joined to the other portion by a 

 hinge ; it was obvious that these two leaves, when placed in a cylinder, would 

 fill the cavity as the original ellipse had done ; both the minor and major 

 axes being at different angles. These leaves being supported from beneath 

 by rods with ball and socket joints, the wear in any direction, would be com- 

 pensated by the extension of the leaves, as their constant tendency was to 

 become horizontal. The rocking rods, acting at points on the leaves, where 

 the preponderance of surface was in one direction, enabled the water to open 

 and close them, with that easy motion which was so much desired in heavy 

 lifts. 



Mr. Jordan wished it particularly to be understood, that he hal directed 

 attention to the disc valve, hoping that from its simplicity of action, it might 

 be tried and found serviceable, for the clacks of deep mine pumps, of large 

 diameter, and working under a column of from 10 to 50 fathoms in height. 

 There was little doubt of the valve being tight under ordinary circumstances, 

 and with short lifts, but when a heavy column of water, was allowed to rest 

 upon a valve, the slightest inaccuracy was detected. 



Mr. Homersham differed in opinion with Mr. Jordan, as to the applica- 

 bility of the disc valves to deep mine-pumps. He conceived there would be 

 a certain amount of difficulty, in constructing them so as to be perfectly 

 tight, under a heavy column of water, and the spindle or pivot of the valve, 

 would require to be of large diameter, to insure its being strong enough to 

 bear the pressure. It was also necessary, for the perfect action of the valve 

 of a pumping engine, that it should be closed, by the time the piston of the 

 pump arrived at the top, or the bottom of its stroke ; this could only be ac- 

 complished, by the weight of the valve, balancing the maximum velocity of 

 the water put in motion through it, so that it should begin to close, as the 

 flow of w.tter diminished, and be quite closed, when the motion of the piston 

 ceased ; this, he conceived, would be difficult to accomplish, with the valve 

 then under consideration. 



Mr. Palmer remarked, with reference to these objections, that the opinions 

 given, were clearly in opposition to facts, deduced from fifteen months ope- 

 ration of this pump, raising water under a vertical column of 40 feet, during 

 which period, the slip or loss of water, approached nearer to the calculated 

 result, than any pump duty that had come under his observation. In refer- 

 ence to the second objection, it was quite clear the valve-spindle must be of 

 adequate strength, to support the column of water the pump had to lift : he 

 believed that no greater evil (considered in an abstract sense) could result 

 from the use of a large spindle, than an increased friction at its bearings, and 

 a corresponding loss of velocity in the fall of the valve. These evils were, 

 however, neutralized by increasing the excentricity of the spindle, and 

 thereby enlarging the valve's area above the spindle, which increased area 

 would always be considered, in reference to the altitude of the column of 

 water above the valve, in order to insure the least loss of water, and at the 

 same time to avoid the percussive action, so detrimental in other pumps. As 

 regarded the third objection, namely, that there woidd be great difficulty in 

 keeping the disc-valve perfectly tight ; he would remark, that in the pump 

 referred to, the minor axis of the piston was not sensibly worn, while the 

 major axis was shortened T^Tttl'S of an inch, but still preserving the true ellip- 

 tic form, and fitting the pump as accurately as when first put into action, 

 although the piston had made upwards of 16,800,000 double strokes, and 

 had travelled over a rubbing surface exceeding 2,100 miles, during the up- 

 ward or effective stroke. The wear of the clack-valve at the major axis was 

 less than ^^jth part of an inch, while at the minor axis it had undergone no 

 change, although the number of beats it had made equalled the number of 

 strokes of the pump. The modifications of the elliptic disc piston and valve 

 into the trapezium form, as proposed by Mr. Galloway, appeared to him to 

 be attended, not only with a considerable increase of cost in the manufacture 

 and the fitting of the trapezium valve, and the working-barrel, but also in- 

 creasing the amount of rubbing surface, with a corresponding amount of 

 wear and tear, as compared with a pump having the elliptic valve performing 

 the like amount of duty. The two semi-elliptic valves proposed by Mr. 

 Galloway, were ingenious, but they were contrived with the view of remedy- 

 ing an evil that did not really exist in the discelliptic piston valve, namely, 

 wear and tear of the minor axis, and leakage at the parts supposed to be 

 worn ; nor would the action of the two elliptic leaves, he conceived, be as 

 efficient as the simple elliptic disc piston valve. 



