VALVES AND THEORIES.

Gisborne Times, Volume XLVIII, Issue 4602, 4 July 1917, Page 6

VALVES AND THEORIES.

THE MACHINERY CASE.

NIVEN & CO. v. P.B. FARMERS’ MEAT CO., LTD.

CASE FQR THE DEFENCE

'At tlie Supreme Court yesterday morning the hearing of evidence for the defence in the case J. J. Niven, Ltd. v. P.B. Farmers’ Meat Co., Ltd., was continued. The plaintiffs were represented by Mr Skerrett, with him Messrs Lusk and Nolan, and the defendants were represented by-'Mr Myers, and with him Mr Burnard. T'ne case is being heard before Bis Honor ( Mr Justice Hosking and a. special jury. ■The witness Rutherford was further cross-examined by Mr Skerrett, and in answer to question's, said that there was evidence that interior portions of the valve cage had been broken before the mushroom head entered the cylinder.’ It might have taken a day or less than a day. in the third case he said the valve had been broken without affecting the operation to any great extent. Ihe conditions were bound to produce a derangement of the working of the valve, but he did not think it would cause any abnormal noise. Although the spindle was loose the valve would work loose in the valve cage and the marks on the head were caused by ruction. It was, in his opinion, the most feasible theory he could suggest. Witness examined the broken cage and said that there .were no marks on the portion which he suggested had been played upon by the head. A repetition of the marks would smooth the surface. He accounted for the marks on the piston to a certain extent to a portion of the valve, and that portion must have protruded from the valve opening before falling into the cylinder. By the marks, the piston was hammering the. head of the mushroom, for what period he could not say. Whichever edge of the mushroom the piston struck it struck with very considerable force. He would not say that it caused the piston head to rotate. The piston may have been slack. „ • Do you admit it did rotate r—lo a certain extent either on the rod or with the rod. ' , Would not die blows on the mushroom head he very severe?—No. Could you make such blows until a hammer?—Yes, easily. Would it not be unusual for an engine to be run with a slack piston ? Yes, hut a machine is not infallible. To alter the piston considerable force would be required ?—Yes. If it were not the impact what made the piston rotate? —I don’t know.

SHOULD THE NOISE HAVE BEEN NOTICEABLE?

As an engineer tell the jury if those blows should not have been recognised by a competent engineer?—l say it may not have been noticeable. Witness in further replies said compressors had a broken heat. He could not explain the sound. It consisted of a variety of sounds limning in a series. The noise was regular. A man working a machine would come to know the beat. All compressors had the noise. It was caused through the re-seating of the mushroom or its seat. , , i _l The operator might not be able to detect anything wrong. When, an accident happened he simply wiled for spare valves. His Honor: With the high revolution machine would more work be required to be done by the spring. • No if the valve were suitable. Does more work require to be done on Linde springs than on Niven springs?—Personally I don t think so. He did not tliink any more work would be thrown upon the spring. All compressors made a noise, but the Niven’s compressor at Tailiape made a noise different to others. Were the valve striking the seat and also the stop the noise would be confused. Mr Skerrett: It would be a warning noise and ought to have been Witness said that lie was speaking in the light of his own experience. After the third valve was broken he bad the valves examined twice a week and found many broken springs, of which he ha.fi no indication. Ihej ran short of springs and he had to make springs out of old ones. # Be had never known of broken springs before. With ffhe new valves, supplied oy Nivens the breaking of springs had almost been eliminated, and he haa only had one broken spring since January. What induced him to reduce the lift was to endeavoi to re duce the excessive wear on the valve, and as a consequence reduced the clearance. ... , Mr Skerrett: This is a mushroom head from a Linde valve. _ Witness: I am not going to ? say whether it is a Linde on. a Niven s. His Honor: All you will say is that it is a valve. . , To Mr Skerrett:. Assuming the mushroom dropped into its seat the pressure of gas would force it back and would not be there when the piston reached it. Unless it was held by the guides it would go-back to the SG To Mr Myers: The bottom marks on tlie mushroom head of the third va ve might be due to the piston on to the wobbling action of the head m the seat.

ENGINEER’S EXPERIENCES AT LONGBURN.

Archibald Keith mechanical en<nueer, said he had had about. 26 ?ears experience operating; refrigerating machinery. For the last 1/ years he had been chief engineer at the freezing works at Longbum. At ■chat place they had a low speed, 2oton Linde compressor for 17 and he had no trouble with it. D e did not remember a spring breaking. Early in January, 1915, Niven s completed the erection of a 36-ton JN at ional compressor, direct coupled, it had not been satisfactory and was not so now. The delivery valves weie the trouble and the machine was alright except for the delivery valves. When the machine was installed JNiven’s gave the working revolutions at 150. Two delivery valves had fallen into the cylinder. The first fell, in on February 1, 1915, the result being that the cover was broken. Mi Me Grath was in charge of the machine and one of the company s own engineers was on watch. Witness was not on. the spot, at the time.. Mi McDonald succeeded Mr McGrath and on February 23 the second valve fell in. Mr McDonald was there, the machine was being stopped when thevalve fell in. Until the bump was felt no warning of anv kind had been given. After that witness exercised a good deal of care in looking at the valves and during the season seven more valves were discovered broken. There' bad been no warning indications. The appearances of the Longburn mushroom heads presented prac- ■ ticallv the same appearance as the ... the Poverty Bay mushroom head, and the others had marks on them, he had not had any experience of accidents caused by valves getting into ' the cylinder except at Longburn, had he experienced broken springs. , A good many .springs were i?. roke P ’ during the' first season with Niven s machine. In the last three breaks witness found the mushroom, head broken and the spring was intact. •The noise made by the Niven machine was like a continual light hammering. His Honor: It went twice as fast as the other. Mr Myers: Not necessarily so. Mr Skerrett: It had a larger number of valves and went twice, as fast. Witness, continuing, said that he heard no difference in noise when all the valves were right and when, one was broken. The diameter of the top of the first set of valve* was

7-16 and the internal diameter of the cage was 2 11-16. While the valves were going wrong Niven s sent new ones, some of which he understood were their own make. The ratio of clearance area to piston area in the second lot was 2 4 per cent. Those valves did not work well, and Nivens sent along a new kind, the kind, which was in use at present. In this - the ratio of clearance area to piston area was about 4 per cent. There was no wear oil the valves now, hut they still wanted altering. : They were an provement on the first' lot. a.nei'e had been no broken springs since tlie new valves had been fitted, but he had had trouble with springs in the older valves. He could not say whose make the new valves were.

FREEZING CAPACITY OF A NIVEN MACHINE.

His Honor remarked that lie would have to put some standard of valves before the jury. Witness said he understood Niven’s to say that the first lot was Linde valves and some of the later lot, he thought, might have been. Niven’s valves and made at Napier. ■ Mr George Nelson spent some time at the works the latter part of last year in connection with the valves. Witness held the opinion that the valves were not long enough. Mr McCarthy had taken up the question of clearance before Mr Nelson commenced his investigations at Longburn. Mr McCarthy had taken indicator cards. In the first valves at Longburn they had an extended spindle. In the earlier part of 1916, a separate stop was introduced in place of the extended spindle. Witness thought he had broken stops during the year. Niven’s were now making new covers and valves for Longburn on similar lines to Tailiape. Witness had inspected the Poverty Bay compressor, and would not care to work the machine with a repaired bed plate and the same valves in use. He would he afraid of accidents. : To Mr Skerrett: The Linde valve produced was' similar to those first fitted to the machine. As far as he could say the valves which broke the first year had extended spindles. Soms were thickened. After Mr Nelson went Home the shape of the mushroom was altered. New valves failed at the fillet without' breaking the spring. Mr Nelson was supposed to have sent the valves out from England. The present valves were put in in March of this year. The new valves were telescopic—a piston worked inside the valve and was quite unlike any of the other types. The machine was very good with regard to economy of fuel. The maximum number of carcases frozen by this machine was 1700, and it had often exceeded the maximum prescribed by the makers—lsoo. This machine was an evolution on existing types of compressors, and other makers were approximating towards this type. Witness had made frequent alterations in the valves and had reduced the lift. He had noticed no alteration in the quantum of work. He did not remember whether Mr McCarthy advised a reduction in the lift.

To Mr Myers: The i verage of 1600 carcases per day was obtained with the telescopic valves. If the clear anee had been larger the valves would have been better. That was his experience so far as valves were concerned.

To the foreman of the jury: If new valves were put in and the bed plate repaired he would consider the machine workable for a - time.

His Honor: Assuming good valves ? Witness: It may be alright.

mr, McCarthy in the witness BOX. Charles McCarthy, consulting engineer and member of the firm of F. L. G. James, said he entered the firm in February. 1916. Prior to this witness had been -working with Me James in connection with Poverty Bay and other works. He had had about 27 years experience with refrigerating machinery, and this extended nearly all meat refrigerating countries. He had operated refrigerating plants, as well as supervising. Witness had had several conversations with Mr George Nelson with regard to the valves in these compressors. At that time he held the opinion that the valves were not suitable fort the class of work they had to’ do. His Honor: All valves do the same class of work? Witness: Tlie same principle existed in all valves, but he referred to the materials of which the. valves . were constructed. Continuing, witness, said that Mr Nelson was making investigations and he thought he would solve the problem. He was of opinion that the National valve in New Zealand was not sufficiently tough, and when he got. Home he would investigate materials. Mr Nelson had an idea that the valve was too heavily loaded, and he made experiments to reduce this. After Tailiape and Longburn witness had - a doubt .about the •Poverty Bay machine, and when the machine was started he gave instructions for it to be run as slow as possible. Unless the gas was very rich for the gas engine, the low rate could not be maintained. In September, 1916 witness was called in by tlie company at Longburn to investigate their machine. Ho took indicator cards of the machine. "Witness went to laihape and took cards there. Witness went to Gisborne and took cards here. This was in November. Un September 28 he had all valves taken out and examined. Mr Chadwick was there. Witness returned to Wellington and wrote to Niven and Co., drawing the firm’s attention to the valves which he considered were defective and had insufficient clearance. Witness had had a good many conversations with Mr Chadwick over the valves. When visiting the works in company with Mr Chadwick the clearance was measured and m some cases was found to be less than Longburn Then witness came to the conclusion that the trouble was due to fatiguing of the metal, due to excessive shock, the shock being due to not sufficient clearance. there was no other conclusion he could come to. Witness concluded that Niven s had made a mistake m making the patterns of the valve cage. Had the cage been made 7-16 larger than the mushroom hed instead of 3-16, theie would have been no shock. Ine machinist’s error, did not appear on all the valves; what he had said regarding tlie increased clearance applied to ail the valves.

OAN GUARANTEED SPRINGS BE GOT?

Witness produced specifications of machinery for Taihape works signed A. C. Mitchell, superintendent engim eer, specifying the number of revolutions per minute for compressor and gas engine. The number,for the compressor was 160. In liis experience witness said he had never had. a spring break, but he had had springs wear out-. , c An advertisement was produced offering for sale springs- of guaranteed quality. In answer to His Honor, witness said that a spring had an ordinary life. + His Honor: Have you ever bought springs on that recommendation ? Witness: No. ■ •. .. Asked the date of the journal in which the advertisement appeared, witness said August 1912. , His Honor: Perhaps they have given up guaranteeing springs since then. Witness produced a plan of : the Vilter valve showing the clearance to be greater than the lift in the valve opening.: Witness said he had never heard of a valve designed like the Poverty Bay, valve produced referring to clearance. ' The clearance in the Poverty Bay valve was less than the original Taihape and Longburn valves.

When witness wrote his EAqoufi letter hi October he did not know .that a writ liad been issued. He bad seen nothing since then to make him alter the opinion expressed in his letters of October. The Poverty Bay machine was installed after the ■ trouble $t Longburn and Tailiape was knoiyn. In reghi-d to the indicator cards he took at Tailiape, Longburn and Gisborne, there was not much excessive pressure at Tailiape, and at Longburn and Poverty Bay the excess pressure was much the same. The aim of all engineers was to equalise the pressure as much as? possible in the cylinder and the discharge pipes. This could be done to within a pound, but if the difference was more than 31bs excess lie' considered that there was something wrong. There were several machines working at almost a difference of one pound. This was so now at Tailiape. Tlie result of this excess pressure was a shock on the stem of the valve, and excess pressure was due to not sufficient clearance. Nivens did not take any indicator cards off the machines at the three places already mentioned. Williams (1903 edition! on refrigeration referred to pressure on the lines stated by witness. Redward’s book on Indicator Diagrams for refrigerating machinery was also quoted by witness. The writer considered lOlbs excess pressure too much. Other authorities were quoted to support the principle that insufficient clearance meant excess pressure. It was all a question of clearance, and this was illustrated by the results obtained at Tailiape. His Honor asked whether there was any reason for withholding payment on' contracts ? Mr. Myers: There was a number of contracts and a number of disputes. Mr. Skerrett asked His Honor to leave that point until he had a chance of dealing with the correspondence.

RHYTHM OR RATTLE ?/

Continuing, witness said he had frequent visits to Waipaoa and watched the icompressor. He could say that she was not worked at full capacity, and could have been had the valves been all right, In February. 1916, witness certified to a payment of £IBB2 on the, contract. The machine was on the job but it was not erected. Up to the time the compressor broke down it had not had a full test, and had worked a number of hours equivalent to a little over five weeks. This was on a light loan. Witness had been in close touch with the three machines since they had been erected. The machines made a tremendous rattle and this should not be so. The word rhythm could not apply to compressors. In the present Longburn valves no rattle or heat could be heard. His Honor: Then the sound was made by the valve hitting the stop. To Mr. Myers :He had seen the machine two or three times since it had broken dowu, and lie had arranged for the broken parts to be kept under lock and key. He had known stops to break leaving the springs intact. That happened in the case of, the one before the Court. The spring had uot-lost its resiliency. With his experience lie would have nothing to do with working the machine with a repaired bed plate and similar valves. If the cover broke, pretty well £IOOO of ammonia would be wasted. To put in another make of compressor the whole of the foundations would have to be taken up, costing up to £250. Tlie cost of dismantling and removing the present compressor would be about £3O. The Crossley engine for, the purpose of being coupled with the compressor had to have the shaft reduced. If a new compressor of another make were'put in a new crank shaft would be needed. A new shaft would run from -£250 to £3OO. The English makers did not, as far as he knew, make high speed compressors of 36 tons. There were, three or four American firms that he knew of who did. The valve cages of Poverty Bay were, he thought, made By Nivens. Mr. Skerrett said it- was admitted they were.

QUESTION OF VELOCITY OF GAS

Witness: As far as he knew the whole outfit, externally and internally, with the exception of the springs, was made by Nivens. During the 1915-16 season the Stern machine was working at its full capacity. To Mr. Skerrett: As a consulting engineer lie was fairly well acquainted with the science of engineering. There was a scientific method for determining the clearance in a compressor. That method was the most certain. The only method was the card indicator. . There must he first the indicator card, hut by what scientific process do you discover whether the clearance area is sufficient?—You take the cards and read them. You won’t get any more out of me. Continuing, witness said that as a practical engineer he did not bother his head about velocity. He could not give in figures the formula for determining a clearance area. There was a formula which took into consideration the velocity of the gas. It had been said that the ammonia passed through the cylinder at the rate of 173 feet per second. Witness: He could not work it out, and no man in the room could. Witness was asked to look at some calculations by Mr. Mitchell, and said they were nearly correct. He denied that 324 cubic feet of gas were admitted to the cylinder. Tweny-five to 30 per cent, would have to be taken off. Assuming that the cubic contents ot the cylinder were 324 feet, witness denied that 24-155ths of 324 would give the cubic measurement to which the gas would he compressed. , What is the formula for determining the velocity of gases ?—Knowing the cubic contents and the area 1 could .determine the velocity, but it would take too long to work out. Mr. Skerrett quoted a formula, and asked witness whether it was right. Witness: If Mr. Skerrett’s formula were right the gas would pass througn the cylinder at the rate of 1613 feet per minute. ' , Mr. Skerrett considered that it was 50- feet of ’compressed gas that would pass through the cylinder, not 324. Witness : The contents of -a cylinder was the area swept by the piston, less from 20 to 30 per cent. Velocity could only be worked out by Rankin’s law. The less gas the less velocity. If 20 per cent, was taken off that would be in Mr. Skerrett’s favor. The gas admitted into the cylinder had no velocity, even when compressed. The volume.of gas which had to pass through the clearance was the compressed volume. , . If 50 cubic feet is the volume ot compressed gas, that passed througn the clearance area, can you say why vou have assumed for the basis or your calculations that 324 had to pass through ?—He did not agree with that. “The 324 was the volume swept by the piston. The volume to which the gas was compressed could he ascertained, but. he could not answer the question because it was not practical. He had applied no test but the card test. When Mr. , Myers mentioned 173 feet that was the first he heard of it.

HIS HONOR TAKES WITNESS TO TASK.

Mr. Skerrett went on to question witness as to the time of opening of the valves, and referred to questions he had put to Mr. A.‘ S. Mitchell. Did Mr. McCarthy take notice of the questions at the time?

Witness: I took no notice because you were juggling with figures.His Honor: Witness does not seem to be taking the matter seriously. You would do your side of the case more good by answering the questions. , ]yir. Myers: I have not called Mr. McCarthy as a scientific witness. Mr. Skerrett: Oh. . His Honor (to witness) : You seem to regard the questions as a lingo joke. Why don’t you answer “Yes” or “No”?' . Witness: The questions are not practical i /• Proceeding, witness said that there, was a relation between the area or clearance and the superficial area of the piston head. He had no fiutliority for this here, but lie dared say lie could find one. The ratio was about 6 per pent. He went on practical experience with the indicator cards. Without the movement of the piston there was no displacement of gas in the cylinder. Provided the revolutions remained the same, the. quantity of gas admitted increased in proportion to the increase of stroke. Twice the quantity of gas could he admitted. The. valve would be open longer with the longer movement of the piston. With double a given stroke under given conditions, the delivery valve would open twice as long. ■ I suggest that this is an absurdity r —I still maintain it. Witness continuing: After Mr James left witness acted as consulting engineer. It was not impossible to get any certificate from witness until the case started. The instructions related to No. 1 contract. Witness refused to say that it related to the case abandoned in that Court. Do you not know that it related to a claim that a substantial reduction should be made on account of certain duplicated parts not required?—l knew nothing of the deduction ior £477 at that time, Ho went on to say that he prepared a certificate for over £4OOO which Mr Lysnar refused to allow him to issue to Nivens. The preparation of the certificate was a mistake. He admitted receiving a telegram dated July 31, ‘from the defendant company informing him that he had no authority to issue the certificate as no such amount was due under the terms of the contract. He was not throughout the whole of the business under tlie dominance of Mr Lysnar. The first complete examination of the compressor was made on September 28. Mr Skerrett asked if he received a telegram telling him to be- non-com-mittal with regard to a compressor from Nivens. Mr Myers explained that the telegram referred to a transaction with another compressor.

THE MATTER OF CERTIFICATES

Witness declined- to issue certificates, acting under instructions from the company, for the pipe contract until certain legal points were settled. . , ~ You told us that the impact of ' the collar upon the stop was about three tons per minute. How do you arrive at that ? —'Witness explained. Surely you have fallen in an error. —I have riot. Surely at the monment tlie pressure was exerted, the pressure on the back and! front was equalised? —It was not in this valve. The indicator cards showed, that. . What dud this card (produced) represent?—No 15 card enlarged. I understand you to say . that 4-lb increase would prevent an? knocking p -Yos* I understand that you say that there is insufficient clearance in this valve? —I am sure of it. That defect would begin to operate as soon as tlie machine was started. Yes. If the machine was run at 150 revolutions you would expect it would have full presure for that- number ol revolutions? —Yes, varying with suction pressure. The -deficiencies of clearance wo mu result in knocking of valve stem. y es _ .At the rate you mentioned about three tons per minute? —Yes. And you would find other indications of inability of gas to escape? —There would be also superheating of delivery pipes but an engineer would put that down to make of machine. Would there be other indications? —-Jerky motions of gas engine as weight came upon the compressor. Would that be very noticeable?— Very noticeable and has been.

WHAT THE LOG-BOOK SHOWED,

Isn’t th& log-book a record of the satisfactory working of. the machine? —I have not examined the log-book for that. _ , You liavn't examined the for the purpose of this case —I have not.

Witness examined an extract from the log-book. He said he did not see anything wrong with the figures, except that the machine was running on light load. The machine from the records was working satisfactory; Insufficient clearance would have «o bearing on the figures'. The IL'e months’ working were not a fair test for the machine. Your view of a test is working three months at the height of the season ?—Yes. The machine was delivered before the Stern but not very long. It was on its bed when the Stern arrived. All liapnened. within a month. The Crossley engine was there before the National compressor. Witness admitted that he had made a mistake in sayipg Mr. Chadwick was present when he took the cards. The valves were found to be in perfect condition in September. ' Mr Skerrett: It was working during the months of July. August and September and; the valves were found to be in perfect order in spite of the alleged defect ? —The machine had not done a month’s , working on hours then. ' ~ During the discussion with Messrs Chadwick, and Burgess, Mr Chadwick says no suggestion was made ot any error in the valves. Do you contradict it?—Yes. I told him the valve was too small. Did vou not toll him the cage was too small?—Yes, about that tune. Mr Chadwick would swear that no gauge was made or used in his presence in September. Will you swear that this is not so ? —I will swear it. Witness: Probably Mr Chadwick d'id not value my opinion much. Mr Skerrett: Your opinion! I think so. . , , , . Witness continuing, said that h© would not deny that Mr Burgess said that he would prefer the- National valves on the -Stern; lie did not remember saying it. There' was some discussion about the cover. Beforetaking the indicator cards in Isovemher, witness examined /the main valve of the delivery pipe;/looked at the suction pipes, crank, cross head, three gauges. Hei proceeded to give othei details of his w examination before taking the cards. He did! not look at the valves on the distributing condensor. He looked at the pass pipeWhy did you look at these pipes ? —To see that they were properly closed.

HORSE-POWER OF THE COMPRESSOR,

Proceeding, witness said that he, had worked out the horse-power for the compressor. I understand you to suggest that if there is insufficient pressure more than normal horse-power was required to drive the compressor- 0 —! have

worked out' the total horse-power on the card.

Have you worked out the quantity of horse-power that the conditions shown by the card required?—Here is No 2 card worked out.

What horse-power would you expect would bo required to work the compressor?^—lt varies with the load on it.

I see you have on this card horsepower 27. Is that excessive horsepower or not; what does it represent. ? —lt represents excess over what it should be. Witness offered to work cards out for the morning. Continuing, witness said that when lie wrote the letter of October 6. no .cards had been taken off the Poverty Bay machine. Witness had.no recollection of suggesting using No ’ 3 Linde valves on the Taihape compressor when it was converted. Mr Mitchell swore that you did. Will you contradict him? —I do. Is the volume of gas drawn into a compressor a constant quantity irrespective of back pressure? l —lt varies with back pressure. Can you understand Mr A. S. Mihcheil saying that it did not? —He might have misunderstood you. H Mr Mitchell understood the question? —I say he didn’t. Do you agree with Mr A. S. Mitchell that Linde valves were unsuitable for high-pressure machines. From my experience I have come to the same conclusion. A National compressor would not be suitable for Linde valves ?• No. Isn’t the National a high speed machine —No. Isn’t .150 revolutions a high speed? —No. At this stage the Court was adjourned: until 10 o’clock this morning- ______