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Home My WebLink About1897-002 Proposal - Cobb & Hesselmeyer 6 s, JR: FIRST cl~ H. T. HESSELMEYER .y EDW. S. COBB COBB & HESSELMEYER Expert Examinatimis and Reports on \ Power Plants. DESIGNING AND Designs, Drawings and. Specifications ~ 41 ~CONSULTING for Machinery. Expert Tests. ME C HANI CAL ~0 HYE RATJLI C ENGINEERS r O~~ r~ O - 1 _ _ ~aA.tce~~w - ~ ~-~-tir~ ~ , ~ ~ ova.., ~ ~ a ~ 4! r rw ',~U w ee~ ,dam y~2~~..~ ' .a fz ~.wl o -r-.~ Vi e. i ~ ~ ~ ~ ~ ~zu~ p f you are using a pipe line for conveping . water this will interest you SENT & MEYERDERKS, PRS. 40 CALIFORNIA ST. HE apparatus herein illustrated ♦ has been designed to use in connection with pipe lines conveying water for power or other uses, and is for the pur- pose of absolutely preventing the fluc- tuations of pressure, which occur in such lines when the flow of water is suddenl}' checked or changed. The phenomena of " RAM " or shock in pipe lines have been observed by all, and many devices have been suggested for effecting a protection for the pipe against bursting, or other serious injury; but so far as we have been able to learn, none have been applicable ~Bt3a"ESSC~M~7ER HrDR_gU~IC EAGINCERS to all conditions and few have been effective aN raaNC scu under any conditions. The application of an air chamber of suit- able dimensions gives to a pipe line an elas- ticity to resist shock, not attainable with any other known device-and as far as receiving and absorbing the shock is concerned, proba- bly no better device will be forthcoming. But where the flow of water in the pipe line , is used to drive water wheels, and when the quantity of flow is regulated by increasing or diminishing the area of cross-section of the nozzle, the use of an air chamber has pre- sented some difficulties. To illustrate, consider a pipe line, flowing full of water at a normal velocity under head or pressure, and discharging through an orifice of variable cross-section. Let this pipe be provided with an air chamber placed at a point PATENTED AUGUST a, 1BaT Fig. 1 preferably near the point of discharge; suppose that the cross-section of the discharge orifice be suddenly decreased, then the normal velocity entrapped in the air chamber, and closes auto- of flow in the pipe line must be as suddenly matically when the water discharging from the checked; and the excess energy of the moving air chamber has reduced the pressure therein mass will be spent in, first: compressing to a down to normal conditions. It will be observed greater degree the air confined in the air that under this arrangement- chamber; and, second: in giving an increased 1st. Only that amount of water is wasted velocity of flow through the reduced discharge which is passed through the air chamber area. as an exact measure of the energy of The air in the air chamber thus compressed the " RAM " overcome. above its normal pressure will react and cause a return flow or rebound of water in the pipe line, 2nd. That under normal conditions, the pres- the energy of which will be as great as the origi- sures in the air chamber and pipe line nal excess energy of flow, less the loss due to are equal, and hence the automatic stop friction, and this alternate flow and rebound valve between air chamber and pipe will continue in action until friction has ab- sorbed the excess energy of the moving mass. 3rd. That in most situations, the simple The alternate flow and rebound above referred arrangement shown in Figure 1, may be to, cause coincident increase and decrease of ve- used, as the confined, non-fluctuating, locity of flow at the discharge orifice, and render excess pressure in the air-chamber is the attainment of uniform speed in the water an ideal medium to operate a safety wheel a matter of great uncertainty; even, when valve as there shown. the best known forms of governors are in use. 4th. That if an exceptionally close re- The apparatus here illustrated, embodies the gulation of pressure in the pipe line is elastic air chamber to receive and absorb the desired, other arrangements not shown shock, and the reaction of the air compressed may be used, wherein the discharge above normal is prevented by introducing an valve from the air chamber is operated automatic stop valve between air chamber and by an hydraulic cylinder, the piston of pipe line as shown-thus absolutely preventing which receives on one of its faces the any rebounding action, and coincident fluctua- pressure of the air-chamber, and on its tion of pressure at the discharge orifice, opposite face a constant pressure, from The water which enters the air chamber the accumulator shown, exactly equal during the compression of the air therein is to the normal working pressure of the discharged through a suitable waste valve at pipe line. the side. This valve being opened by the 5th. That full information in regard to this excess of pressure above normal, that was device as applied to any pipe line under 4 any conditions, will be cheerfully given. EXTRACT PALACE HOTEL, FROM SAN FRANCISCO, CAL. Pale and 011E-Half Editorial SAN FRANCISCO, Sept. 10th, 1897. ,N " ENGINEERING NEWS." MESSRS. COBB & HEssULMEYER, Mechanical and Hydraulic Engineers, SAN FRANCISCO. JULv 8, 1897. Dear Sirs : - o~~~~- It gives us very much pleasure, to convey to you our appreciation for the cure you sug- " The reader who has followed gested for one of our Artesian Pumps; namely, the above discussion can now form an intelli- the Check Valve in the Air Chamber. This gent opinion as to the merit of the device of particular pump referred to is a Dow Compound Mr. E. S. Cobb, described in Mr. Richards' Tandem working on an 18-inch well 213 feet deep, raising- water through a 5-inch vertical paper. It appears to us to be an excellent de- pipe 257 feet; thence horizontally 95 feet to cir- vice, and likely to prove effective if properly culating tanks. The discharge being fastened designed. We desire to call especial attention and supported on building wall. The pulsation to the waste valve of this device, which appears being so heavy, prevented us operating beyond a limited speed. We were compelled to shut to us likely to prove the best method for con- down for six hours at night. At your sug- trolling the flow in long pipes and solving the gestion, and sketch submitted, the alteration difficulties in governing the speed of wheels, was made, which resulted in an entire change, and in controlling the pulsations and shocks in scarcely creditable unless practically demon- strated. We are now enabled to run at most the pipe to which we have referred. Such re- any speed and continuously. lief valves should be proportioned to the size of I will further state, that in addition to the the pipe they control, and should be located as above results obtained, less steam is required to near to the nozzle of the pipe as practicable, accomplish the same work. Heretofore, the They should be so loaded as to open automatic- ordinary life-time of our leather packing in water cylinder when the pressure in the conduit rises some- has been six weeks, it is now in y two months and has shown no outward sign of what above the normal working pressure, and giving way. would then act to prevent the further increase In conclusion would say, that we shall take of pressure in the pipe. The water wasted much pleasure in showing the same to any one through them would be comparatively small you may send along. In the meantime, accept in amount and would furnish believe the dear sirs, the assurance of our highest appre- > we ciation, I remain, cheapest and simplest way of taking care of the Very truly yours, energy that appears when the velocity of flow JOHN E. BURNESS, in the conduit is checked." Chief Engineer. COBB & HESSELMEYER DESIGNING AND CONSULTING Mechanical and Hydraulic ENGINEERS Plans Estimates Specifications Supervision Tests 421 MARKET STREET COR. FIRST SAN FRANCISCO, CAL. TELEPHONE, BLACK 2403 w