US3055629A - Depressuring valve - Google Patents

Description

Sept- 25, 1962 P. c. JURS ETAI.

DEPRESSURING VALVE 2 Sheets-Sheet 1 Filed June 26, 1959 .3 u l4 49 Y VERNON 4. FLETCHER,

PET E R C U u Rs JOSEPH R VANOVERVEEIU INVENTORS :FIE l ATTOE/UE ys Sept- 25, 19 2 P. c. JURS ETA].

DEPRESSURING VALVE 2 Sheets-Sheet 2 Filed June 26, 1959 rIIEI I VERNON 4. Fara/15g, PETE R C. J u R s JOSEPH PVANOVERVEEN INVENTORS ATTOPA/EYS United States Patent Ofllice 3,055,629 DEPRESSURING VALVE Peter C. Jurs, Oakland, Joseph P. Van Overveen, Lafayette, and Vernon A. Fletcher, Oakland, Calif., assignors to Shand and Jurs Company, Berkeley, Calif,

a corporation of California Filed June 26, 1959, Ser. No. 823,191

1 Claim. (Cl. 251-25) This invention relates generally to valves and valve systems suitable for depressuring operations. More particularly, the invention pertains to depressuring apparatus applicable to storage and process vessels.

Many products are commonly stored in pressure tanks or vessels. For example, liquified petroleum products are stored in pressure tanks at a pressure dependent upon that of the temperature and vapor pressure of the liquified components. For example, with liquified butane or propane, the normal tank pressure may range from approximately 30-200 psi. for temperatures ranging from 70 It is customary to provide storage tanks with pressure relief valves whereby when the internal tank pressure reaches a predetermined value, the relief valve opens automatically to vent ofl? vapor. This serves to protect the tank against excessive internal pressure which might cause serious injury. However, situations have arisen in which such relief valves have been found inadequate to relieve the excess pressure created within the tank. For example, in the event of a fire in the vicinity of a storage tank, the contents may be heated considerably above normal temperatures so that the relief valve and the piping connected to the tank are inadequate to carry off the vapor at a suflicient rate to properly protect the tank against excessive pressure.

Even if a number of conventional safety relief valves are provided on the tank, such protection is still inadequate because the flame from a fire may impinge only a certain portion of the tank to cause overheating of a localized area of the tank. Within a relatively short period of time, this weakens the metal of the tank so that the tank starts to bulge or blister in this area, after which a rupture often occurs. In such a situation, the conventional safety relief valves will not operate because the pressure in the tank may still be below the safety limits for the tank.

In process vessels such as cracking towers and the like, something may 'go wrong with the process so that the pressure within the process vessel approaches an unsafe limit. Heretofore, when this has occurred, it has been the normal procedure to shut down the entire process. As is well known, this is a very costly procedure. There is, therefore, a need for means for depressuring the process vessels for a short period of time so that a cushion of time is obtained to find out what is wrong with the process.

In general, it is an object of the present invention to provide improved means for rapidly depressuring vessels used for processing and storage.

Another object of the invention is to provide a simplified and reliable depressuring valve which can be operated in emergencies and which is not vulnerable to damage.

Another object of the invention is to provide a depressuring apparatus of the above character which may in- 3,055,629 Patented Sept. 25, 1962 clude means responsive to the wall temperature of the storage vessel to secure emergency tank venting.

Another object of the invention is to provide a depressuring valve of the above character which can be utilized for a large range of pressures and temperatures.

Another object of the invention is to provide a depressuring valve of the above character in which an excellent seal is obtained.

Another object of the invention is to provide a depressuring valve of the above character which opens and closes very rapidly.

Another object of the invention is to provide a depressuring valve of the above character in which dynamic and static pressures are utilized to obtain rapid repressuring of the valve.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a cross-sectional view of a depressuring valve incorporating the present invention.

FIGURE 2 is a detail view taken along the lines 22 of FIGURE 1.

FIGURE 3 is a view partially in cross-section showing the depressuring valve incorporated in a system with a control valve in one position.

FIGURE 4 is a partial view similar to that shown in FIGURE 3 with the control valve in a different position.

As shown in FIGURE 1, our depressuring valve consists of a body 11 which is provided with a vertical passage 12 adapted to be connected to the storage or pressure vessel by a fitting 13. The valve body is provided with two stationary radially spaced concentric valve seats 14 and 16 which lie in a substantially horizontal plane. The valve seats are provided with inserts 17 of suitable valve seat material such as stainless steel. The valve seats 14 and 16 are separated by an annular passage .18 which communicates with an outflow passage 15 that is adapted for connection to suitable means such as a venting pipe (not shown). An annularly contoured pallet '19 overlies the valve seats 14 and 16 and is adapted to seal upon the valve seats 14 and 16.

A dome-like cover 21 encloses the space 20 overlying the pallet 19 and is secured to the valve body 11 by suitable means such as stud 23. The interior of the cover 21 is machined to provide a cylindrical guide surface 24 which is only slightly larger in diameter than the diameter of the pallet .19. A limiting shoulder 26 also machined within the cover 21 forms a limiting stop for engaging the pallet when the latter is in full open venting position as hereinafter described. The upper part of the dome cover is provided with an opening 27 for communicating with a control pipe 28 threaded into the cover.

The pallet 19 includes a metal plate 31 which is provided with a central opening 32. A relatively thin, flexible impervious diaphragm 33 of suitable material such as stainless steel is provided as a facing on the lower side of the plate 31. In certain applications a nonmetallic or synthetic material can be used for the diaphragm. As shown, the diaphragm 33 covers the entire bottom surface of the plate and has its outer margins clamped to the plate by suitable means such as a clamping ring 34 secured to the plate 31 by bolts 36. It will be noted that the clamping ring 34 is radially spaced outwardly from the outer valve seat 16 so that the diaphragm 33 may readily engage the valve seats.

An elbow 37 is mounted on the body in the passage 12 and faces downwardly into the passage 12. The elbow 37 is adapted to connect to a control pipe 38 threaded into the side Wall of the body.

In FIGURE 3, the depressuring valve is shown incorporated in a system in which the control lines 28 and 38 are connected to a suitable control device such as a three-way valve 41 which is schematically illustrated. The three-way valve consists of a body 42 and a movable valve member 43 which is provided with a T-shaped passageway 44. The T-shaped passageway is adapted to communicate with openings 46, 47 and 48 in the body 42. The opening 46 is connected to the control pipe 38 and the opening 47 is connected to the control pipe 28. The opening 48 is connected to a pipe 51 which opens to the atmosphere.

As shown in FIGURE 3, the depressuring valve is mounted on a vessel or tank 52 by the fitting 13.

In FIGURE 4, the control line 38 is shown directly connected to the tank rather than to the valve.

Operation of the depressuring valve and system described above is as follows. Normally, the valve 41 is positioned so that the pipes 28 and 38 are interconnected. Under such a condition, the pressure in the dome chamber 22 assumes the same value as that in the tank because the tank pressure is directly applied to the dome through the interconnected piping 38 and 28. The pressure in the dome chamber 22 acts downwardly upon the pallet 19 over an area corresponding to the mean effective diameter of the annular seat 16. Since this area is substantially greater than that corresponding to the effective diameter of the seat 14, the pallet 19 is normally urged downwardly into sealing engagement with both seats 14 and 16.

The tank pressure also passes through the opening 32 in the metal plate 31 and between the diaphragm 33 and the metal plate. This pressure has a tendency to cause flexing of the portion of the diaphragm 33 which overlies the annular passage 18 as shown particularly in FIG- URE 2. This occurs because the annular passage 18 is exposed to the atmosphere through the outflow passage 15. This differential in pressure causes the slight bulging of the diaphragm shown in FIGURE 2. This bulging of the diaphragm helps to establish an effective seal between the two seat rings 14 and 16.

Now let it be assumed that an over-pressure condition occurs in the tank or vessel 52 and that it is desired to depressure the vessel. This is accomplished by moving the movable member 43 to a position so that line 28 is connected to line 51 to freely vent the dome chamber 22 to the atmosphere. This sudden reduction of pressure in the dome chamber causes the pressure in the vertical passageway 12 to actually pop the pallet 19 upwardly into a position in which it rests against the annular shoulder 26. The tank is then freely vented through the passage 12, the annular passage 18 and out through the outflow passage 15.

Now let it be assumed that the pressure in the tank has been reduced to a safe value and that it is desired to close the depressuring valve before the tank pressure has been reduced to atmospheric. The valve 41 is then actuated to again interconnect pipes 28 and 38. At the time the valve 41 is moved to this position, the vapors are still passing through the vertical passage 12. Certain of these moving gases or fluids are trapped by the downwardly facing elbow 37 and pass into the dome chamber 22. By utilization of the downwardly curved elbow 37, it is apparent that the dynamic as well as static pressure is applied to the dome chamber 22. Since the pressure in the dome chamber 22 rapidly assumes the same value as in the passage 12, the pallet 19 almost instantly moves to a closed position in sealing engagement with the seat rings 14 and 16. Thus, it can be seen that by the movement of the valve 41 between the two positions shown, the depressuring valve is rapidly moved between sealing and venting positions.

It will be evident from the foregoing that the depressuring valve and system has many applications in which it can be used. The valve 41 can be controlled in any suitable manner. For example, the valve can be controlled locally or remotely by mechanical, electrical, hydraulic or pneumatic means that is manually or automatically actuated. Switches, fusible plugs and other types of sensing devices can be utilized to determine when the valve should be open and closed. The depressuring valve, in particular, has been found to be useful for protecting storage tanks containing liquified petroleum products. Because of the relatively large venting passages provided, the storage tank pressure is dropped very rapidly without danger of bursting the tank although the tank may be in or near a fire. The depressuring valve is also particularly useful in certain processes in which process vessels or tanks are utilized. When it is noticed that a dangerous pressure is being produced in a process vessel, the pressure in the process vessel may be rapidly reduced by venting the vessel to the atmosphere through the depressuring valve. As soon as the pressure in the tank has reached a safe limit, the depressuring valve can be repressured or closed. This will provide a cushion of time in which an analysis can be made to determine what has occurred in the process to cause the elevated pressure in the process vessel. If the trouble is not discovered before the pressure again rises to a dangerous level, the pressure vessel can again be depressurized. The same procedure can be followed until the trouble in the process has been eliminated. This is a much more economical way of finding a trouble in the process rather than shutting down the process.

Although the pallet 19 has been described as having a central opening 32, if desired the central opening can be eliminated when it is not desired to apply pressure between the diaphragm and the pallet. Although the depressuring valve has been described utilizing the pressure from the tank or vessel to which the valve is connected, it is readily apparent that if desired an external source of pressure such as plant air or bottled nitrogen can be utilized for maintaining the pallet in a closed position.

Since the use of conventional diaphragms such as rubber or other resilient material has been eliminated, the diaphragm is not likely to be injured or fail at high temperatures. However, where the valve is unlikely to be exposed to heat, conventional diaphragms of rubber or other resilient material may be utilized. In addition, when the diaphragm is formed of stainless steel, the valve itself can be utilized in process or storage vessels containing vapors which would normally attack conventional diaphragms. The valve itself is quite simple in construction and very reliable in its operation. For a given size, it has a relatively high venting capacity.

We claim:

In a depressuring valve adapted to open to vent fluid from a pressure system, a body having an inlet passage for connection with a source of fluid pressure and having a venting discharge passage, a pair of radially spaced concentric seats formed within the body, the opening through the inner seat being in communication with the inlet passage and the opening between said seats being in communication with the discharge passage, a pallet having one side of the same adapted to seat and seal upon both of said spaced concentric seats, said pallet including a rigid annularly contoured plate, an impervious, relatively thin flexible diaphragm mounted on the lower face of said plate, means securing an outer annular portion of said diaphragm to said plate, means forming a fluid chamber on the other side of the pallet, the plate being formed with an opening extending therethrough and communicating between the chamber and the adjacent surface of the diaphragm to apply the fluid pressure in the chamber to the diaphragm whereby the annular portion of the diaphragm References Cited in the file of this patent between the seats bulges to form tight sealing engagement UNITED STATES PATENTS with the radially spaced seats, means external of the body providing communication between the inlet passage and 1 22: 5:? lg the closed chamber to permit rapid fluid flow between the 5 2O64343 Finley 1936 inlet passage and the closed chamber to rapidly move the 2417994 sheets 1947 pallet to a closed position when the pallet is in an open 2:456:913 1943 position and to maintain the pallet in a closed posi ion 2,480,712 Carbon Aug 30, 1949 after it has been moved to a closed position, and means 557,53 Dram et 1 June 19, 1951 for venting the chamber to the atmosphere for permitting 10 2,577,967 Hughes Dec. 11, 1951 the fluid pressure within the inlet passage to rapidly move 2,732,856 Jurs J an. 31, 1956 the pallet from a closed to an open position. 2,882,006 Reinecke Apr. 14, 1959 2,928,413 Hansen Mar. 15, 1960

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