US2258469A - Silencer for water hammer - Google Patents

Description

1R1-233 SR g l lmmna 0R zgzsaww j Oct. 7, 1941. .1. PODOLSKY 2,258,469

SILENCER FOR WATER HAMMER Filed Jul 19, 1939 /a ah 20 60 2y" 2/. w I f z zz 2 I V I aco f0 W 23/,

n1. Acoustics Patented Oct. 7, 1941 starch scam UNITED STATES PATENT OFFICE This invention relates to improvements in silencers for water hammer.

More particularly it relates to devices for preventing the loud pounding sound which sometimes occurs in a system of water pipes, especially when a faucet is closed quickly, producing a sudden stoppage of outflow.

In the absence of a cushioning air space, suitably located in the pipe system, the momentum of the column of water that was flowing toward the faucet piles up pressure on the walls of the pipe, compressing the water and stretching the walls, to a very slight extent in each case, from which, by reflection, a wave of high excess pressure, herein for brevity called a hammer wave, oscillates back and forth in the pipe system with a series of shocks sounding like hammer blows. The general effect is distressing to hearers; the stresses imposed on the piping system may occur in parts of the system remote from that where the disturbance originated; and, as these are in the nature of bursting stresses, they may involve danger to the piping.

To relieve water hammer, it is customary to provide air chambers to absorb the shock; but

the air of the air chamber often becomes soon absorbed by the water; and, if that air is not replaced at intervals, the hammering is experienced. Also valves in the nature of safety valves are used, but these discharge water out of the system, and in other respects give trouble.

The present invention requires no air in its chamber, makes no discharge from the system, and needs no attention after being once properly installed. It provides a water chamber having ports guarded so that all hammer waves reaching the silencer become absorbed there, or so destroyed or diminished that no hammer blows are heard.

By the invention an energy-absorbing waterfilled chamber is provided, herein called a neutral chamber because it automatically becomes re-set at a pressure intermediate between the normal pressure of the system and the excessive pressure induced by the momentum in the closed system. This chamber receives the initial wave of increased pressure, absorbs the energy of it, and then discharges itself back into the system at the lower or normal pressure of the system which immediately supervenes, preferably making this discharge at a slight distance in the system from where the shock was received. The chamber has two ports, one for admitting the pressure of the hammer wave, the other for discharging pressure built up in it by the hammer wave, each port being guarded by means which assures its operating for its particular purpose.

As illustrated herein, the ports are on opposite sides of the chamber; each has a valve;

each valve has a spring tending to seat the valve; and there is an extension of the main piping from the first port through a return bend around to the second port, the latter being on the opposite side of the chamber. The valve at the first port seats outward with respect to the chamber, and ordinarily is kept closed by any suitable means which is strong enough to hold the valve closed notwithstanding such routine or ordinary increases of pressure as may occur in the piping system without danger ,of water hammer, yet not so strong that it would fail to yield readily to an excessive increase of pressure such as results when a faucet is quickly closed. For illustrative example, to which however the invention is not limited, this strong seating means may be a spring applying to the valve a closing pressure fifty per cent greater than the normal static pressure in the system when the water therein is quiet. The valve at the second port seats inward toward the chamber, from the system, and is pressed toward its seat by a spring which supplements the system pressure only weakly. The pressure in the chamber therefore will stand at a figure which exceeds the static pressure in the piping system by only about the strength of this weak spring.

A pressure wave, of the sort whose hammer effect is to be prevented, travels through the system with a speed approximating that of sound through water. It has the general effect of compressing the water and stretching the walls of the pipe. The compressibility of water is so slight that sometimes the impact of the wave on the walls is like that of a hammer blow. Arriving at the first port of the neutral chamber, having the valve which opens inward of the chamber, the extraordinary pressure attending the wave overcomes the spring there, above described as being substantially stronger than the static pressure of the water, and forces it inward of the cylinder. Some of the energy of the wave is thus absorbed by this spring, but more of it is used in compressing the water that is in the chamber, with whatever air is diffused in that water, and in stretching the chamber walls. This may involve some slight inflow of water through the first port into the neutral chamber, whose internal pressure rises as that chamber absorbs the energy of the wave which enters through the port. The pressure wave however proceeds in part along the continuation passage and reaches the second port at practically the instant when pressure is up inside the chamber, applying wave pressure to the outer face of the inward closing valve at this port. This opposes the pressure within the chamber, for the instant; but when the absorption of energy of the pressure wave is completed the high pressure within the chamber finds its relief outward through the second port, which it can open as the outside wave pressure falls, until the pressure within the chamber is no more than the outside pressure of water plus weak spring. Thus the hammer-threatening wave becomes split into two parts which oppose each other, and, to a degree, cancel each other, at the neutral chamber. But one part is absorbed there; the reflection of any part not so absorbed is so small as to be harmless; and the wave resulting from the release of the pressure piled up in the chamber is a sort of delayed reflection, which is both diminished and is out of phase with whatever wave was reflected from the part which struck the outside of the second port. The result there fore is harmless both in that the hammer wave is destroyed and that 'the displacement of water which occurs in the action is wholly within the system.

The foregoing is as good a statement as I can make at the present time of the action which occurs within the device herein described, which I have found effective to prevent water hammer, but I reserve the right to give a further or different explanation if and when more becomes known about it. To enable any person to construct and operate the hammer preventing device successfully, regardless of what may be the explanation of the action, I show in the accompanying drawing an embodiment which I have found successful as applied to domestic hot or cold water systems.

It will be understood that the utility of the invention is not limited to such systems, and that the particular way of constructing and applying the elements of the combination can be varied.

It is intended that the patent shall cover, by suitable expression in the appended claims, whatever of patentable invention shall be found in the disclosure herein made.

In the accompanying drawing: Figure 1 is a side elevation of a device embodying the invention;

Figure 2 is a medial section of a portion, in elevation as in Figure 1;

Figure 3 is a plan, in section on the line 3-3 of Figure 2;

Figure 4 is an elevation in section on vertical surfaces indicated by the line 4-4 in Figures 2 and 3;

Figure 5 shows in elevation the separated parts of one of the inlet valves.

Referring to the drawing. and bearing in mind that the particular form here shown for illustrating the invention is only one of the various ways in which the device may be constructed, the embodiment here illustrated has a neutral chamber I0 conveniently formed between a dome II and a base l2 on which that dome is screwmounted, or otherwise secured in a water tight manner. The base has means of any suitable sort, illustrated by the pipe-threaded nipple It, to provide for its connection to the water pipe system which is to be protected. The connec tion may preferably be such that the basal passage I6 is a continuation of a run of pipe in the pipe system to which it is connected; and, if that be a domestic hot water system, the connection may preferably be made at a location near the heater; but this is not the only place where connection may be made. The device may in fact be connected in any manner which will result in its receiving the wave of increased pressure of water, that would make the water hammer which the device is intended to prevent. The tubular base passage l 6 branches to the port l8, herein called the first port, of neutral chamber I0, and has a tubular continuation of its other branch through a 180 bend of piping 20 to an elbow 22 by which, through coupling 24 the second branch arrives at the outside of the second port of chamber l0, located at the top of the dome, below the nipple 26 and marked 28.

At each of these ports, I8, 28, there is means normally closing the port, the particular means chosen for illustration being for each a pop valve 30 seated by a spring 3| or 32 caged within a hollow screw 34, whose open upper end has a cross bar 36 with a small interior boss 38 for centering the top end of spring 3! or 32 which surrounds the stem 40 of the valve and presses that valve toward its seat. The valve which serves the first port I8 seats outward from the neutral chamber I0, and therefore yields inward from the passage when the pressure in the piping system is sufficient, the piping system being typifled by the passage [6 at this place. This spring 3| preferably is made with strength sufficient for it to remain closed against all ordinary static pressures in the piping system, and against such routine variation of pressure as the system may casually undergo without water hammer being experienced if the device of the invention were not present, but not so strong that it will not open when a hammer wave reaches it. Valve 30 which serves the second port 28 seats toward the chamber, and therefore is held closed by any hammer wave, but yields outward when the pressure within the chamber exceeds that of the piping system, tvpified at this point by pressure in the elbow 22. In ordinary situations the spring 32 for this valve will be relatively weak, adding little to the seating effect of the water pressure which is at the time being found on the outside of this valve.

Although springs are illustrated for maintaining these valves closed during static periods, this being ordinarily the most convenient form, the invention is not limited to this way of maintaining the ports normally closed.

The apparatus is applicable to piping systems of all variet es and sizes where water hammer may be found. Each port l8 and 28 is sufficiently r presented herein as being single, but it is an o vious equivalent that each or either of them ma have plural openings, or be of different size r arrangement. as may be convenient. For an illust ative example of operation, let it be assnmed that the device is applied to a domestic hot water svstem fed by a municipal street supply so that the normal static pressure of water in the system is pounds per square inch, commnnly called the street pressure, and the observed pressure developed in the system by a hammer wave is 300 pounds. In such a case one might reasonably use a pound spring 3| at port l8 for holding the valve closed outward against the static system pressure and its normal variations insufficient to amount to hammer lfii ACUUSTlCS Wave; and might use a pound spring 32 for acting with the system pressure toward the inward closing of the valve at port 28. Ordinary fluctuations of pressure from the normal of 65 pounds would then be expected not to affect the silencer; but upon the arrival in passage 16 at the silencer of a wave of increased pressure of the order of 300 pounds, being a hammer wave, the valve at I8 will yield and pressure in the neutral chamber I8 will become built up to a high degree, because its port 28 is simultaneously held closed by the arrival of the same wave of excess pressure at the outside of the valve at port 28, overbalancing any pressure built up by that wave within the chamber which might tend to open the valve at port 28, The energy absorbed in the compressing of chamber contents will be trapped by the closing of its inlet valve at l8 the instant any return flow might begin. The part of the hammer wave which has passed into that part of the system consisting of the port l8 and chamber I0 thus becomes separated from that part of the hammer wave which passes along through the continuation of passage I6 around to the outside of port 28. These branches of the wave are temporarily opposed to each other at the port 28 and valve 32; but, when the fraction of pressure wave outside of port 28 has receded, the high pressure within the chamber can relieve itself outward through port 28down to whatever low pressure exists there on the valve by reason of the weak spring 32 plus the system pressure of the instant. Therefore the chamber l0 becomes immediately ready to receive and absorb energy of another hammer wave--whenever such may come. Meantime as the said discharge from the chamber could not occur until the pressure in the system outside of its port 28 had fallen by reflection of that portion of the hammer Wave which was there, this delay has separated the discharge of the chamber 10 from the peak of the wave, and thus has dissipated the intensity of whatever wave effect is reflected from the silencer back into the system, without a blow sharp enough and intense enough to make a hammer sound having been experienced.

While the embodiment illustrated has springs 3|, 32 to set the valve shut, and to maintain them so under static conditions, the major forces which control these valves in action are the static water pressure and the pressures which result from hammer waves. These pressures would work to produce the effect described, even though the springs were not present. Being present, the springs maintain the valve silently stationary in the absence of water hammer, and so prevent the normal fluctuation of pressure in the system from causing audible opening and closing of the valve when they are not needed to perform their func. tion of preventing water hammer.

As the chamber is always completely filled with water, after whatever air was left in it at the installation has been absorbed by the water, no considerable volume of inflow of water accompanies the building up of the high pressure in the chamber; and the effect of the apparatus is practically as instantaneous as is the impact of the wave.

Although the discharge of the chamber In through port 28, in the arrangement illustrated, is immediately into the continuation 20, 22, of the passage l6, this discharge might, if desired, reach that passage only through one or more additional neutral chambers like chamber l8, each having entrance and discharge ports and. valves similar earth to l8 and 28; set in series out of the discharge which is illustrated in Figures 1 and 2.

On the other hand the discharge port l8 from the single illustrated chamber ll] might be set in the base I2 of that chamber, beside the inlet port l8, thus makin a more immediate connection for the chamber to discharge to the passage [6; In that case the passage 16 might terminate in the base, or might continue to other parts of the piping system.

The size of the chamber and its connections Will naturally be made in suitable relation to the size of pipe in the system which is to be protected. In case of more capacity being needed, one or more additional chambers, or series of chambers, can be connected to the system in parallel with each other.

I claim as my invention:

1. A silencer for Water hammer comprising a water chamber, having walls for confining water of water hammer waves against escape to atmosphere; and a water passage, adapted for being connected to a water piping system; said passage having two ports into said chamber, which said ports are spaced apart from each other along the passage in sequence from said connection; one of these ports having a valve mounted to be opened by pressure of liquid from the passage inward toward the chamber, and the other of these ports having a valve mounted to be opened by pressure of liquid from the chamber outward toward the passage.

2. A silencer as in claim 1 in which one or more of the valves is arranged with means tending to maintain the valve seated.

3. A silencer as in claim 1 in which the outward-seating valve is nearer to the pipe system than is the outward-opening valve, as measured along the said passage from the said connection.

4. A silencer as in claim 1 in which the outward-seating valve and the outward-opening valve are on mutually opposite sides of the chamber.

5. A silencer for water hammer comprising a Water chamber, having walls for confining water of water hammer waves against escape to atmosphere; and a water passage adapted for being connected to a water piping system; said passage having two ports into said chamber, which said ports are spaced apart from each other along the passage in sequence from said connection; there being a return bend of piping in the passage between these ports; one of these ports having a valve mounted to be opened by pressure of liquid from the passage inward toward the chamber, and the other of these ports having a valve mounted to be opened by pressure of liquid from the chamber outward toward the passage.

6. A silencer as in claim 1 in which the said outward-seating valve has means exceeding the normal static pressure of the piping system, tending to keep that valve seated; and the said outward-opening valve has relatively weak means for supplementing the system pressure in the direction of seating thereof against pressure in the chamber.

7. A silencer for water hammer comprising a body having a base with a passage adapted for connection to a piping system; a cover secured on the base, there being a chamber between the base and the cover; a port from the passage through the base into the chamber, with a valve therefor opening inward toward the chamber; a port through the cover into the chamber with a valve therefor opening outward from the chamher; and an extension of the said passage to the second said port; the external walls of said body cover and passage being closed except for the connection into the piping system.

8. A silencer for water hammer comprising a body containing a chamber having walls for confining water of water hammer waves against escape to atmosphere, and having two ports, one of which has agyalv enopemng inward toward the chamber and the other of which has a. valve 10 opening outward from the chamber; and means for connecting the outer sides of both ports to the piping system whose water hammer is to be silenced; the external walls of said body and 5 connecting means being otherwise closed, being non-yielding, and the said chamber and other space which the walls contain being, in normal operation, filled with only water of said system.

JACOB PODOLSKY.

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