CA2252874A1 - Pilot-operated safety relief valve assembly - Google Patents
Pilot-operated safety relief valve assembly Download PDFInfo
- Publication number
- CA2252874A1 CA2252874A1 CA 2252874 CA2252874A CA2252874A1 CA 2252874 A1 CA2252874 A1 CA 2252874A1 CA 2252874 CA2252874 CA 2252874 CA 2252874 A CA2252874 A CA 2252874A CA 2252874 A1 CA2252874 A1 CA 2252874A1
- Authority
- CA
- Canada
- Prior art keywords
- fluid
- pressure
- control fluid
- piston
- relief valve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D16/00—Control of fluid pressure
- G05D16/14—Control of fluid pressure with auxiliary non-electric power
- G05D16/16—Control of fluid pressure with auxiliary non-electric power derived from the controlled fluid
- G05D16/166—Control of fluid pressure with auxiliary non-electric power derived from the controlled fluid using pistons within the main valve
Abstract
An assembly and method for controlling the opening of a safety relief valve (10) exposed to a system fluid pressure and containing a control fluid which controls the opening of the safety relief valve (10) is shown. The assembly includes a pilot valve (30) connected to the safety relief valve (10) and adapted to respond to a predetermined pressure of the system fluid for permitting flow of the control fluid. A regulator (34) receives the control fluid and operates to reduce the pressure of the control fluid with a predetermined amount. The safety relief valve (10) opens in response to the reduction of the control fluid pressure, and the remaining control fluid pressure modulates the opening of the safety relief valve (10).
Description
CA 022~2874 l998-l0-29 W O97/41496 PCT~US97/00944 PrLOT-OPE~ ED S~FEl~Y ~ ~,T,n~ V~L~E ~ ~ MnR~.y ~ Field of the Invention This invention pertains to a safety relief valve assembly and method and, more particularly, to such an assembly and method in which a pilot valve 5 operates a safety relief valve, and a regulator is provided which cooperates with the pilot valve for modlllAtin~ the degree of opening of the safety relief valve.
Ba~ ul.d of the Invention Pressurized vessels and conduits are comm--nly fitted with pressure 10 relief valves to prevent the pressure of fluid inside the vessels and conduits from exceeding a prescribed limit beyond which the vessel, conduit, or equipment corlnected thereto, could rupture or be damaged.
A typical pressure relief valve has an inlet in fluid communication with the main fluid line and an outlet connected to an exhaust line. A piston, or 15 valve meçh~ni.cm, is provided which is normally m~int~ined in a closed position by a compressed spring. The compression of the spring is adjusted to keep the piston in its closed position until the fluid on the inlet side ~tt~in.~ a predetermined pressure. When this occurs, the piston moves to an open position, fluid flows into the inlet, through the valve housing, and out through20 the outlet, thereby relieving the pressure. Once the pressure is reduced to apoint below the predetermined pressure, the spring moves the piston back to its closed position, and normal fluid flow through the line resumes.
Safety relief valves of this type must maintain a sealed closure of the vessel or conduit under normal service con~lition.~, and must achieve minim~l 25 "blowdown", i.e. the difference between the opening pressure and the closing pressure. To ~ccomp~ h this, and to achieve increased pelru~ ance in other respects, safety relief valve assemblies have evolved which are controlled by a piloting device which senses the pressure of the fluid in the vessel or conduit and actuates the valve as a function of this pressure almost instantaneously 30 to achieve rapid an.d complete openingA and closures with relatively small blowdown.
Present day pilot-operated safety relief valves are generally of the "pop"
type which includes a pilot relief valve which opens at a predetermined CA 022~2874 1998-10-29 - pressure, thus causing the safety relief valve to open. In a typical arrangement of this type, the dome pressure (i.e., the pressure which holds the main valve closed) is reduced to atmospheric pressure, and the piston thus moves to a full open position, almost inst~nt~neously. However, this causes several proble_s. For ~ mple, extremely large qllAntities of fluid are discharged from the safety relief valve in response to the quick opening of the piston. Also, the extremely quick opening and closing of the piston causes an inordinate amount of wear and stress on the piston and its associated components as well as the associated flow conduits. Further, under cel~
resonant conditions, the piston will "chatter~, that is, open and close at a very rapid rate which renders it dysfunctional and subject to prPm~hlre failure.
Still further, these type of pressure relief valves and associated pilot valves are relatively complicated and expensive.
Therefore, what is needed is a pilot-operated safety relief valve in which the amount of fluid discharge from the valve is modulated, and wear and stress on the valve components and the associated flow conduits are minimi7:ed. Also needed is a valve of the above type that does not chatter and is relatively inexpensive and simple in construction and operation.
Sllmm~ry of the Invention The present invention, accordingly, provides an assembly and method in which a pilot valve is provided which controls the operation of the safety relief valve, and a regulator modulates the operation of the pilot valve, and thwe~le the opening and clo~ing of the safety relief valve. To this end, an operating fluid is provided in a chamber which provides a pressure that normally biases the piston of the safety relief valve to a closed position. The pilot valve is connected to the safety relief valve in a m~nner to vent the operating fluid from the chamber and thus enable the piston to open. The regulator is connected to the pilot valve in a mAnnÇr to control the tli.~r.h~rge of the operating fluid so that the safety relief valve gradually opens.
Thus, major advantages are achieved with the assembly method of the present invention since the amount of fluid discharged from the safety relief valve is reduced, and wear and stress on the valve components and the CA 022~2874 1998-10-29 - associated flow conduits are minimi7ed. Also, the safety relief valve does notchatter and is relatively in~Xp~n~cive and simple in construction and operation.Brief De~cription of the Drawin~
Figure 1 is a partial sectinnAl-partial s- h~m~t.ic view of the safety relief 5 valve assembly of the present invention.
Figure 2 is an enlarged sectional view of the pilot valve and the regulator of figure 1, showing the pilot valve and the regulator their closed positions.
Figure 3 is a view, simil~r to figure 2 but depicting the pilot valve and 10 the regulator in their open positions.
De~l;u~ion of the Preferred Embodiment ReferIing to figure 1 of the drawings, the lefelellce numeral 10 refers, in general to a safety relief valve including a housing 12 having an inlet passage 12a formed through one wall thereof for receiving a conduit 14 15 cont~ining a fluid under pressure. An outlet passage 12b i9 also provided in the housing 12 which ~xten~l.c at right angles to the inlet passage 12a for exhausting the fluid under conditions to be described.
A movable piston 16 is provided in the housing and, in its closed position, rests against a seat bushing 18 disposed in the housing 12 in 20 ~lignment with the inlet passage 12a. The piston 16 moves up and down in the housing 12 as viewed in figure 1, and a cylindrical g~ude member 20 is disposed in the housing above the bushing 16 for guiding this movement. A
cover 22 extends over the upper portion of the housing 12 to define a chamber 24 between the upper portion of the piston 16 and the cover. A control fluid is 25 contained in the chamber 24 for bi~.cinF the piston 16 to its closed positionresting against the seat bushing 18, as shown in figure 1. In this contQxt., theupper end portion of the valve 16 is curved to define a larger surface area than that of the lower end of the valve. Since the pressure of the control fluidin the chamber 24 is essentially the same as the pressure of the ~y~lelll fluid 30 in the inlet passage 12a, as will be ~.x~ ined further, the force exerted on the upper portion of the piston 16 by the control fluid is greater than the force exerted on the lower end of the piston by the system fluid due to the differences in these areas. A spring 26 is also disposed in the chamber 24 , CA 022~2874 1998-10-29 WO97/41496 PCT~US97/00944 - -- which adds to the downwardly-directed forces acting on the upper end portion ~f the piston 16.
A port 22a is provided through the cover 22 and cnmmllnicates with the chamber 24. The port 22a is connected, via a conduit 28, to a pilot valve 30, shown schematically in figure 1, for controlling the fluid pressure in the chamber 24 in a m~nn~r to be described. A port 12c is provided through a wall of the housing 12 in comm-ln~ tion with the inlet passage 12a, and is conn~cted, via a conduit 32, to the pilot valve 30. A branch conduit 32a also connects the conduit 32, and therefore the port 12a, to a regulator 34, also shown sch~m~tically. The regulator 34 regulates the operation of the pilot valve 30 in a m~nn~r to be described, and to this end, a conduit 36 connects an outlet of the pilot valve 30 to an inlet of the regulator 34, and a conduit 37 connects the outlet of the regulator to the outlet passage 12b of the safety relief valve 10. These various connections between the safety relief valve 10, the pilot valve 30, and the regulator 34 will be described in detail.
A~s stated above, the forces caused by the pressure of the control fluid and the spring 26 in the chamber 24 acting against the upper end of the piston 16 normally bias the latter member to its closed position shown in figure 1. However, when the pressure of the control fluid in the chamber 24 is relieved by the valve assembly of the present invention, the piston 16 is forcedupwardly away from the seat bushing 18 and the pressurized fluid in the inlet passage 12a is relieved and some of the fluid flows through the inlet passage 12a, the housing 12 and exits the housing through the outlet passage 12b.
Since the safety relief valve 10, per se, does not form a part of the present invention, the more specific details of same, including the provision of seals, and the like, associated with the valve have been omitted. In the latter cont~rt. a full, detailed disclosure and description of the safety relief valve 10 is cont~inerl in U.S. patent No. 4,917,144, ~ igned to the ~ ignee of the present invention, the disclosure of which is incorporated by ~ er~ ce.
Figure 2 depicts the details of the pilot valve 30 and the regulator 34.
The pilot valve 30 includes a housing 40 having an inlet passage 40a connected to the conduit 32 for receiving the system fluid from the safety relief valve 10 (figure 1). A passage 40b is also provided in the housing 40 CA 022~2874 1998-10-29 WO 97/41496 PCT/US97/00944 . - -- which is connected to the conduit 28 ~xtqn-ling from the chamber 24 (figure 1)of the safety reliefvalve 10, and an outlet passage 40c is connected to the conduit 36 extenl1ing to the regulator 34.
A centrally-located bore 40d ~tan~.q though the length of the housing 40 and commllnicates the passages 40a-40c. The upper portion of the bore 40d is enlarged and receives a piston 42. Reciprocal movement of the piston 42 in the housing 40 is permitted by an ~nmll~r diaphragm 44 e~t~nrling across the enlarged portion of the bore 40d and secured between the upper end of the housing 40 and a cover 46 ~ten~ing over the latter end. The cover 46 is secured to the housing 40 by a threaded bolt 48 ~ten~ling through corresponding threaded openings in the cover and the housing.
The piston 42 has a stepped outer diameter defining four portions with vary~ng diameters including an upper stem 42a having a reduced di~meter.
The stem 42a extends through aligned central openings in the diaphragm 44 and a center plate 50 extenrling over the exposed portion of the diaphragm 44.
An intermediate portion 42b of the piston 42 extends immediately below the diaphragm 44 and a nut 52 is in threaded engagement with the stem 42a to secure the center plate 50 and the diaphragm 44 between it and the shoulder defined between the stem 42a and the piston portion 42b.
The piston portion 42b ~rten(ls into the bore 40d, a necked-down portion 40c of the piston 42 extends immediately below the portion 42b, and a control stem 42d extends below the necked down portion. When the piston 42 is in its closed position shown in figure 2, the lower end of the piston portion42b abuts an internal flange 40e ~rtenrling inwardly from the bore 40d. The flange 40e has a seal ring 52 mounted to its inner surface which, in the closed position of the piston 42, ~ ounds the necked-down piston portion 42c with a clearance therebetween. An annular groove 40e' is formed in the upper surface of the flange 40e to provide for fluid c- mmllniÇ~tion from the passage 40a, through the groove 40e' and the bore 40d, and including the space between the flange 40e and the necked-down piston portion 42c, and to the passage 40b. This equalizes the fluid pressure in the passage 40b, and therefore the chamber 24 of the pressure relief valve 10 to that of the system pressure in the cha_ber 40a, for reasons to be described.
CA 022~2874 l998-l0-29 WO97/41496 PCT~US97/00944 --- A sleeve 54 is mounted in the bore 40d of the housing 40 and ~srt~n~lq below the flange 40e in a spaced relationship thereto. The sleeve 64 is sized so as to fit snugly within the bore 40d, and a seal ring 54a ~t~n(l.~ between the outer surface of the sleeve 54 and the corresponding surface of the housing 40 d~fining the bore 40d. A seal ring 54b is mounted on the inner surface of the sleeve 54 and, in the closed position of the piston 42 shown in figure 2, engages the outer surface of the lower end portion of the stem 42d to block flow commlmication between the passages 40b and 40c through the bore 40d.
A spring 56 is applied to the upper stem 42a of the piston 42 to urge the piston downwardly as viewed in figure 2. Since the spring 56 is of a conv~ntionz.l design, it is not shown in detail and its associated components are not shown, in the interest of clarity. The downwardly-directed force exerted by the spring on the piston 42 is opposed by an upwardly-directed force exerted against the diaphragm 44, and therefore the piston 42, by the pressure of the system fluid from the conduit 32 that enters the inlet passage 40a of the housing 40. The design is such that, if the pressure of the system fluid stays within normal limits, the force of the spring 56 acting on the piston 42 will exceed the upwardly-directed force applied by the fluid pressure acting on the diaphragm 44, and mz~in~in the piston 42 in its closed position of figure 2. However, if the force of the system fluid acting against the lower end of the diaphragm 44 is greater than the force of the spring 56 acting against the piston 42, the central portion of the diaphragm, and the1ero~e the piston 42, will move upwardly. This causes the stem 42d of the piston 42 to clear, or rise, above the seal ring 54b and attain the position shown in figure 3. This commllni~tes the passage 40b and 40c through the bore 40d and thus permits the control fluid from the chamber 24 (figure 1) of the safety relief valve 10 to flow through the conduit 28, the housing bore 40d, and to the outlet conduit 40c for passage to the regulator 34. Also, in the open position of the piston 42 shown in figure 3, the upper portion of the stem 42d of the piston 42 engages the seal ring 52 to prevent fluid communication between the passages 40a and 40b. The signifi~nce of this will be described later.
A blowdown adjustment plug 58 is mounted in the lower portion of the bore 40d. The upper end portion of the plug 58 has a reduced diameter and CA 022~2874 1998-10-29 - nestles within the sleeve 54 in threaded engagement therewith. The plug 58 has a central passage 68a connected to the passage 40b and a radial passage 58b connected to the central passage to permit the above-mentioned flow from the passage 40b, through the bore 40d and to the passage 40c. The lower end 6 portion of the plug 58 and the corresponding internal surface of the housingdefinin~ the bore 40d are threaded and in engagement so that the axial position of the plug, and therefore the sleeve 54, can be adjusted relat*e to the housing 40 by rotating the plug. A seal ring 54a extends between the corresponding surfaces of the plug 58 and the latter housing surface to prevent fluid leakage therebetween. This axial rotation of the plug 58 sets the position of the sleeve 54 relative to the 42d of the piston 42, and thus çn~llesthe blowdown of the assembly to be adjusted, as will be discussed.
The regulator 34 consists of a housing 60 having an inlet passage 60a which is connected to a branch conduit 32a ~xtentling from the conduit 32 and therefore receives the system fluid from the safety relief valve 10 (figure 1). A
second inlet passage 60b and an outlet, or vent passage 60c are provided in the housing 60, and a central bore 60d is provided through the housing that connects the passages 60a, 60b, and 60c.
A valve assembly 62 is disposed in the bore 60d of the housing 60 and includes a piston 64 and a sleeve 66 exten~ing below the piston and in engagement therewith. A center plate 68 is provided in a counterbore provided in the sleeve 66 and engages a seal ring 70 provided in a groove formed in the inner surface of the seal ring defining the counterbore. A bolt 72 ~tenf1.~ through threaded, aligned, central openings formed through the piston 64 and the sleeve 66 and through the center opening in the center plate 68, to connect the center plate 68 and the sleeve 66 to the piston 64. Two seal rings 74a and 74b are respectively located in two axially spaced grooves formed in the outer surface of the sleeve 66 and engages the corresponding surface of the housing d~fining the bore 60d.
The lower end portion of the bore 60d is enlarged and the inner wall portion of the housing 60 d~fining this lower end portion is threaded. A plug 76 is mounted in the lower end portion of the bore 60d and has a bore that defines the inlet passage 60b. The plug 76 has an externally threaded outer CA 022~2874 1998-10-29 surface portion in threaded engagement with the threaded inner wall portion of the housing 60. An annular, upwardly-~xten-lin~ flange 76a ~ n~l.q from the upper end of the plug 76 and, in the closed position of the valve assembly shown in figure 2, the outer surface of the flange 76 engage the seal ring 70 ofthe valve assembly 62.
The pressure of the system fluid from the branch conduit 32a thus acts on the upper end of the valve ~qcemhly 62 to urge it to its closed position in which the seal ring 70 engages the flange 76a of the plug 76. However, when fluid is passed from the outlet passage 40c of the housing 40 to the conduit 36 10 under conditions to be described, the pressure of the fluid in the conduit 36acts against the lower end of the valve assembly 62. The area of the lower surface of the valve assembly 62 is greater that the area of its upper surface, and since the respective pressures of the control fluid and the system are the same for the reasons discussed above, the control fluid pressure acting on the 15 lower end of the valve assembly 62 creates a force that is greater than the force caused by the system pressure acting on the upper end of the valve assembly. As a result7 the valve assembly 62 will move ullw~udly in the bore 60d to its open position and thus permit the fluid in the conduit 36 to pass from the passage 60b, through a portion of the bore 60d and to the outlet 20 passage 60c. The fluid then exits the regulator 34 and passes through the conduit 37 to the outlet passage 12b of the safety relief valve 10 (figure 1). It is noted that the ulJwal d movement of the valve a.qs~mhly 62 is limited by the engagement of corresponding shoulders formed on the sleeve 66 and the housing 60 as shown in figure 3.
In operation, when the system fluid pressure is within a predetermined limit, the pistons 16 and 42 of the safety relief valve 10 and the pilot valve 30, respectively, as well as the valve assembly 62 of the regulator 34, stay in their rlorrn~l, closed position shown in figure 2. As a result, the pressure of the control fluid in the conduit 28 is equalized to the pressure of the system 30 fluid in the conduit 32 through the pilot valve housing 30 and, more particularly, through the inlet passage 40a, the groove 40e', the space between the necked-down piston portion 40c and the seal ring 52, the bore 40d, and the passage 40b. Also, the flow of the system fluid through the safety relief . _. ....
CA 022~2874 1998-10-29 W O97141496 PCTrUS97100944 - valve 10, and the flow of the control fluid from the chamber 24 of the safety ~elief valve 10 through the conduit 28 and to the pilot valve 30, are prevented.However, when the system fluid pressure exceeds the predetermined limit, the corresponding force acting on the lower surface of the diaphragm 44 5 by the system fluid in the passage 40a of the pilot valve 30 forces the piston42 upwardly to the position shown in figure 3. In this position, the upper portion of the stem 42d of the piston 42 engages the seal 52 and thus blocks commllnication between the passages 40a and 40b; while the lower end of the stem 42d is above the seal ring 54b to permit flow of the control fluid from thechamber 24 of the safety relief valve 10, through the conduit 28, and to the pilot valve 30. The control fluid thus passes through the bore 40d of the pilot valve 30 and, via the conduit 36, to the inlet passage 60b of the regulator 34.
Immediately after the opening of the piston 42 of the pilot valve 30 in the above m~nner the pressure of the control fluid passing from the chamber 15 24, through the pilot valve and to the regulator 34 is substantially the sameas the system pressure. Therefore, the pressure of the control fluid in the passage 60b acting against the lower end of the valve assembly 62 of the regulator 34 forces the valve assembly upwardly to its open position against the force applied to the upper end of the latter assembly by the system fluid 20 pressure. The control fluid thus passes from the passage 60b, through the lower portion of the open bore 60d, and to the outlet passage 60c for passage, via the conduit 37, to the outlet passage 12b of the safety relief valve 10 for disposal. After a portion of the control fluid evacuates the cha_ber 24 of the safety relief valve 10 and passes through the pilot valve 30 and the regulator 25 34 as described above, the pressure of the control fluid lowers to the extentthat the resulting upwardly-directed force acting on the lower end of the valve ~.qs~mhly 62 becomes apprr-~nm~t~ly equal to, or just less than, the force caused by the system pressure acting on the upper end of the valve assembly.
When this occurs the valve assembly 62 moves back to its closed position of 30 figure 2.
The design is such that the valve ~.~semhly 62 will move back to its - closed position when a predetermined percentage of the control fluid evacuates the chamber 24 in the foregoing m~nn~r. This is achieved by fabric~ting the g CA 022~2874 1998-10-29 W O 97/41496 PCT~US97/00944 - -- valve assembly 62 in a m~nn~r so that the surface area of its upper end is a predetermined percentage of the surface area of its lower end, which percentage corresponds to the percentage of the control fluid that evacuates the chamber 24. More particularly, and by way of ~x~mple only, the design of the valve assembly 62 is such that the surface area of the upper end of the valve assembly 62 is al-ll.,xi~ tely 73% ofthe surface area of its lower end.
Therefore, after opening in the above-described m?~nn~r, the valve assembly 62 will close back when the pressure of the control fluid in the chamber 24 reaches approximPtely 73% of the pressure of the system fluid, which results in minim~l blowdown.
In the meantime, the piston 16 of the safety relief valve 10 responds to the increased system fluid pressure and to the control fluid pressure reduction in the chamber 24 by moving to its open position to relieve the fluid pressure in its inlet passage 12a to its outlet passage 12b. Since the fluid pressure 16 reduction in the chamber 24 is apprn~im~t~ly 27%, the design of the safety relief valve 10 can be such that the piston 16 will open when the fluid pressure reduction is slightly less than this value, for ~mple, appro~im~tely 24%. ACCOLdi11g to a main feature of the present invention, the remAining fluid pressure in the chamber, in effect, resists the upward, opening movement of the piston 24 and thus insures that the opening movement of the piston is modulated and that it will thus open gradually. During this time, the piston 42 of the pilot valve 30 remz~in.~ in its upper, closed position thusisnl~ting the system pressure in the conduit 32 from the control fluid in the conduit 28 and therefore the chamber 24 of the safety relief valve 10.
When the system fluid pressure is reduced to a predetermined value as result of the opening of the safety relief valve 10 in the foregoing m~nn~r, thepistons 16 add 42 move to their closed positions shown in figures 1 and 2, respectively. As a result, flow of the control fluid from the chamber 24 of the safety relief valve, through the pilot valve 30 and to the regulator in the above-described manner is terminated, and the pressure of the control fluid eql7~ with the ~y~leln fluid pressure through the passages 40a, the pilot - valve 30 and the passage 40b as described above.
CA 022~2874 1998-10-29 W O 97/41496 PCTrUS97/00944 . --- As a result of all of the foregoing, the opening of the piston 16 of thesafety relief valve is modulated and thus prevented from opening too quickly.
Thus, the almost inst~nt~neous opening of the piston of the prior art safety relief valves, as described above, is ~.limin~ted. As a result, the amount of 5 fluid discharged from the safety relief valve 10 of the present invention is reduced and the wear and stress on the valve components and the associated flow conduits is ..~ ed. Also, the pistons 16 and 42 of the safety relief valve 10 and the pilot valve 30, respectively, as well as the valve assembly 62 of the regulator do not "~h~t,t~r" Further, the ~.qs~mhly of the present 10 invention is relatively inexpensive and simple in construction and operation.It is understood that several variations may be made in the foregoing without departing from the scope of the invention. li',x~n~ples of these variations are as follows:
1. The branch conduit 32a of the conduit 32 can be elimin~ted to 15 ~limin~te the application of the system fluid pressure on the upper portion of the valve assembly 62 of the regulator 34, and a spring or the like can be used to apply the latter force.
Ba~ ul.d of the Invention Pressurized vessels and conduits are comm--nly fitted with pressure 10 relief valves to prevent the pressure of fluid inside the vessels and conduits from exceeding a prescribed limit beyond which the vessel, conduit, or equipment corlnected thereto, could rupture or be damaged.
A typical pressure relief valve has an inlet in fluid communication with the main fluid line and an outlet connected to an exhaust line. A piston, or 15 valve meçh~ni.cm, is provided which is normally m~int~ined in a closed position by a compressed spring. The compression of the spring is adjusted to keep the piston in its closed position until the fluid on the inlet side ~tt~in.~ a predetermined pressure. When this occurs, the piston moves to an open position, fluid flows into the inlet, through the valve housing, and out through20 the outlet, thereby relieving the pressure. Once the pressure is reduced to apoint below the predetermined pressure, the spring moves the piston back to its closed position, and normal fluid flow through the line resumes.
Safety relief valves of this type must maintain a sealed closure of the vessel or conduit under normal service con~lition.~, and must achieve minim~l 25 "blowdown", i.e. the difference between the opening pressure and the closing pressure. To ~ccomp~ h this, and to achieve increased pelru~ ance in other respects, safety relief valve assemblies have evolved which are controlled by a piloting device which senses the pressure of the fluid in the vessel or conduit and actuates the valve as a function of this pressure almost instantaneously 30 to achieve rapid an.d complete openingA and closures with relatively small blowdown.
Present day pilot-operated safety relief valves are generally of the "pop"
type which includes a pilot relief valve which opens at a predetermined CA 022~2874 1998-10-29 - pressure, thus causing the safety relief valve to open. In a typical arrangement of this type, the dome pressure (i.e., the pressure which holds the main valve closed) is reduced to atmospheric pressure, and the piston thus moves to a full open position, almost inst~nt~neously. However, this causes several proble_s. For ~ mple, extremely large qllAntities of fluid are discharged from the safety relief valve in response to the quick opening of the piston. Also, the extremely quick opening and closing of the piston causes an inordinate amount of wear and stress on the piston and its associated components as well as the associated flow conduits. Further, under cel~
resonant conditions, the piston will "chatter~, that is, open and close at a very rapid rate which renders it dysfunctional and subject to prPm~hlre failure.
Still further, these type of pressure relief valves and associated pilot valves are relatively complicated and expensive.
Therefore, what is needed is a pilot-operated safety relief valve in which the amount of fluid discharge from the valve is modulated, and wear and stress on the valve components and the associated flow conduits are minimi7:ed. Also needed is a valve of the above type that does not chatter and is relatively inexpensive and simple in construction and operation.
Sllmm~ry of the Invention The present invention, accordingly, provides an assembly and method in which a pilot valve is provided which controls the operation of the safety relief valve, and a regulator modulates the operation of the pilot valve, and thwe~le the opening and clo~ing of the safety relief valve. To this end, an operating fluid is provided in a chamber which provides a pressure that normally biases the piston of the safety relief valve to a closed position. The pilot valve is connected to the safety relief valve in a m~nner to vent the operating fluid from the chamber and thus enable the piston to open. The regulator is connected to the pilot valve in a mAnnÇr to control the tli.~r.h~rge of the operating fluid so that the safety relief valve gradually opens.
Thus, major advantages are achieved with the assembly method of the present invention since the amount of fluid discharged from the safety relief valve is reduced, and wear and stress on the valve components and the CA 022~2874 1998-10-29 - associated flow conduits are minimi7ed. Also, the safety relief valve does notchatter and is relatively in~Xp~n~cive and simple in construction and operation.Brief De~cription of the Drawin~
Figure 1 is a partial sectinnAl-partial s- h~m~t.ic view of the safety relief 5 valve assembly of the present invention.
Figure 2 is an enlarged sectional view of the pilot valve and the regulator of figure 1, showing the pilot valve and the regulator their closed positions.
Figure 3 is a view, simil~r to figure 2 but depicting the pilot valve and 10 the regulator in their open positions.
De~l;u~ion of the Preferred Embodiment ReferIing to figure 1 of the drawings, the lefelellce numeral 10 refers, in general to a safety relief valve including a housing 12 having an inlet passage 12a formed through one wall thereof for receiving a conduit 14 15 cont~ining a fluid under pressure. An outlet passage 12b i9 also provided in the housing 12 which ~xten~l.c at right angles to the inlet passage 12a for exhausting the fluid under conditions to be described.
A movable piston 16 is provided in the housing and, in its closed position, rests against a seat bushing 18 disposed in the housing 12 in 20 ~lignment with the inlet passage 12a. The piston 16 moves up and down in the housing 12 as viewed in figure 1, and a cylindrical g~ude member 20 is disposed in the housing above the bushing 16 for guiding this movement. A
cover 22 extends over the upper portion of the housing 12 to define a chamber 24 between the upper portion of the piston 16 and the cover. A control fluid is 25 contained in the chamber 24 for bi~.cinF the piston 16 to its closed positionresting against the seat bushing 18, as shown in figure 1. In this contQxt., theupper end portion of the valve 16 is curved to define a larger surface area than that of the lower end of the valve. Since the pressure of the control fluidin the chamber 24 is essentially the same as the pressure of the ~y~lelll fluid 30 in the inlet passage 12a, as will be ~.x~ ined further, the force exerted on the upper portion of the piston 16 by the control fluid is greater than the force exerted on the lower end of the piston by the system fluid due to the differences in these areas. A spring 26 is also disposed in the chamber 24 , CA 022~2874 1998-10-29 WO97/41496 PCT~US97/00944 - -- which adds to the downwardly-directed forces acting on the upper end portion ~f the piston 16.
A port 22a is provided through the cover 22 and cnmmllnicates with the chamber 24. The port 22a is connected, via a conduit 28, to a pilot valve 30, shown schematically in figure 1, for controlling the fluid pressure in the chamber 24 in a m~nn~r to be described. A port 12c is provided through a wall of the housing 12 in comm-ln~ tion with the inlet passage 12a, and is conn~cted, via a conduit 32, to the pilot valve 30. A branch conduit 32a also connects the conduit 32, and therefore the port 12a, to a regulator 34, also shown sch~m~tically. The regulator 34 regulates the operation of the pilot valve 30 in a m~nn~r to be described, and to this end, a conduit 36 connects an outlet of the pilot valve 30 to an inlet of the regulator 34, and a conduit 37 connects the outlet of the regulator to the outlet passage 12b of the safety relief valve 10. These various connections between the safety relief valve 10, the pilot valve 30, and the regulator 34 will be described in detail.
A~s stated above, the forces caused by the pressure of the control fluid and the spring 26 in the chamber 24 acting against the upper end of the piston 16 normally bias the latter member to its closed position shown in figure 1. However, when the pressure of the control fluid in the chamber 24 is relieved by the valve assembly of the present invention, the piston 16 is forcedupwardly away from the seat bushing 18 and the pressurized fluid in the inlet passage 12a is relieved and some of the fluid flows through the inlet passage 12a, the housing 12 and exits the housing through the outlet passage 12b.
Since the safety relief valve 10, per se, does not form a part of the present invention, the more specific details of same, including the provision of seals, and the like, associated with the valve have been omitted. In the latter cont~rt. a full, detailed disclosure and description of the safety relief valve 10 is cont~inerl in U.S. patent No. 4,917,144, ~ igned to the ~ ignee of the present invention, the disclosure of which is incorporated by ~ er~ ce.
Figure 2 depicts the details of the pilot valve 30 and the regulator 34.
The pilot valve 30 includes a housing 40 having an inlet passage 40a connected to the conduit 32 for receiving the system fluid from the safety relief valve 10 (figure 1). A passage 40b is also provided in the housing 40 CA 022~2874 1998-10-29 WO 97/41496 PCT/US97/00944 . - -- which is connected to the conduit 28 ~xtqn-ling from the chamber 24 (figure 1)of the safety reliefvalve 10, and an outlet passage 40c is connected to the conduit 36 extenl1ing to the regulator 34.
A centrally-located bore 40d ~tan~.q though the length of the housing 40 and commllnicates the passages 40a-40c. The upper portion of the bore 40d is enlarged and receives a piston 42. Reciprocal movement of the piston 42 in the housing 40 is permitted by an ~nmll~r diaphragm 44 e~t~nrling across the enlarged portion of the bore 40d and secured between the upper end of the housing 40 and a cover 46 ~ten~ing over the latter end. The cover 46 is secured to the housing 40 by a threaded bolt 48 ~ten~ling through corresponding threaded openings in the cover and the housing.
The piston 42 has a stepped outer diameter defining four portions with vary~ng diameters including an upper stem 42a having a reduced di~meter.
The stem 42a extends through aligned central openings in the diaphragm 44 and a center plate 50 extenrling over the exposed portion of the diaphragm 44.
An intermediate portion 42b of the piston 42 extends immediately below the diaphragm 44 and a nut 52 is in threaded engagement with the stem 42a to secure the center plate 50 and the diaphragm 44 between it and the shoulder defined between the stem 42a and the piston portion 42b.
The piston portion 42b ~rten(ls into the bore 40d, a necked-down portion 40c of the piston 42 extends immediately below the portion 42b, and a control stem 42d extends below the necked down portion. When the piston 42 is in its closed position shown in figure 2, the lower end of the piston portion42b abuts an internal flange 40e ~rtenrling inwardly from the bore 40d. The flange 40e has a seal ring 52 mounted to its inner surface which, in the closed position of the piston 42, ~ ounds the necked-down piston portion 42c with a clearance therebetween. An annular groove 40e' is formed in the upper surface of the flange 40e to provide for fluid c- mmllniÇ~tion from the passage 40a, through the groove 40e' and the bore 40d, and including the space between the flange 40e and the necked-down piston portion 42c, and to the passage 40b. This equalizes the fluid pressure in the passage 40b, and therefore the chamber 24 of the pressure relief valve 10 to that of the system pressure in the cha_ber 40a, for reasons to be described.
CA 022~2874 l998-l0-29 WO97/41496 PCT~US97/00944 --- A sleeve 54 is mounted in the bore 40d of the housing 40 and ~srt~n~lq below the flange 40e in a spaced relationship thereto. The sleeve 64 is sized so as to fit snugly within the bore 40d, and a seal ring 54a ~t~n(l.~ between the outer surface of the sleeve 54 and the corresponding surface of the housing 40 d~fining the bore 40d. A seal ring 54b is mounted on the inner surface of the sleeve 54 and, in the closed position of the piston 42 shown in figure 2, engages the outer surface of the lower end portion of the stem 42d to block flow commlmication between the passages 40b and 40c through the bore 40d.
A spring 56 is applied to the upper stem 42a of the piston 42 to urge the piston downwardly as viewed in figure 2. Since the spring 56 is of a conv~ntionz.l design, it is not shown in detail and its associated components are not shown, in the interest of clarity. The downwardly-directed force exerted by the spring on the piston 42 is opposed by an upwardly-directed force exerted against the diaphragm 44, and therefore the piston 42, by the pressure of the system fluid from the conduit 32 that enters the inlet passage 40a of the housing 40. The design is such that, if the pressure of the system fluid stays within normal limits, the force of the spring 56 acting on the piston 42 will exceed the upwardly-directed force applied by the fluid pressure acting on the diaphragm 44, and mz~in~in the piston 42 in its closed position of figure 2. However, if the force of the system fluid acting against the lower end of the diaphragm 44 is greater than the force of the spring 56 acting against the piston 42, the central portion of the diaphragm, and the1ero~e the piston 42, will move upwardly. This causes the stem 42d of the piston 42 to clear, or rise, above the seal ring 54b and attain the position shown in figure 3. This commllni~tes the passage 40b and 40c through the bore 40d and thus permits the control fluid from the chamber 24 (figure 1) of the safety relief valve 10 to flow through the conduit 28, the housing bore 40d, and to the outlet conduit 40c for passage to the regulator 34. Also, in the open position of the piston 42 shown in figure 3, the upper portion of the stem 42d of the piston 42 engages the seal ring 52 to prevent fluid communication between the passages 40a and 40b. The signifi~nce of this will be described later.
A blowdown adjustment plug 58 is mounted in the lower portion of the bore 40d. The upper end portion of the plug 58 has a reduced diameter and CA 022~2874 1998-10-29 - nestles within the sleeve 54 in threaded engagement therewith. The plug 58 has a central passage 68a connected to the passage 40b and a radial passage 58b connected to the central passage to permit the above-mentioned flow from the passage 40b, through the bore 40d and to the passage 40c. The lower end 6 portion of the plug 58 and the corresponding internal surface of the housingdefinin~ the bore 40d are threaded and in engagement so that the axial position of the plug, and therefore the sleeve 54, can be adjusted relat*e to the housing 40 by rotating the plug. A seal ring 54a extends between the corresponding surfaces of the plug 58 and the latter housing surface to prevent fluid leakage therebetween. This axial rotation of the plug 58 sets the position of the sleeve 54 relative to the 42d of the piston 42, and thus çn~llesthe blowdown of the assembly to be adjusted, as will be discussed.
The regulator 34 consists of a housing 60 having an inlet passage 60a which is connected to a branch conduit 32a ~xtentling from the conduit 32 and therefore receives the system fluid from the safety relief valve 10 (figure 1). A
second inlet passage 60b and an outlet, or vent passage 60c are provided in the housing 60, and a central bore 60d is provided through the housing that connects the passages 60a, 60b, and 60c.
A valve assembly 62 is disposed in the bore 60d of the housing 60 and includes a piston 64 and a sleeve 66 exten~ing below the piston and in engagement therewith. A center plate 68 is provided in a counterbore provided in the sleeve 66 and engages a seal ring 70 provided in a groove formed in the inner surface of the seal ring defining the counterbore. A bolt 72 ~tenf1.~ through threaded, aligned, central openings formed through the piston 64 and the sleeve 66 and through the center opening in the center plate 68, to connect the center plate 68 and the sleeve 66 to the piston 64. Two seal rings 74a and 74b are respectively located in two axially spaced grooves formed in the outer surface of the sleeve 66 and engages the corresponding surface of the housing d~fining the bore 60d.
The lower end portion of the bore 60d is enlarged and the inner wall portion of the housing 60 d~fining this lower end portion is threaded. A plug 76 is mounted in the lower end portion of the bore 60d and has a bore that defines the inlet passage 60b. The plug 76 has an externally threaded outer CA 022~2874 1998-10-29 surface portion in threaded engagement with the threaded inner wall portion of the housing 60. An annular, upwardly-~xten-lin~ flange 76a ~ n~l.q from the upper end of the plug 76 and, in the closed position of the valve assembly shown in figure 2, the outer surface of the flange 76 engage the seal ring 70 ofthe valve assembly 62.
The pressure of the system fluid from the branch conduit 32a thus acts on the upper end of the valve ~qcemhly 62 to urge it to its closed position in which the seal ring 70 engages the flange 76a of the plug 76. However, when fluid is passed from the outlet passage 40c of the housing 40 to the conduit 36 10 under conditions to be described, the pressure of the fluid in the conduit 36acts against the lower end of the valve assembly 62. The area of the lower surface of the valve assembly 62 is greater that the area of its upper surface, and since the respective pressures of the control fluid and the system are the same for the reasons discussed above, the control fluid pressure acting on the 15 lower end of the valve assembly 62 creates a force that is greater than the force caused by the system pressure acting on the upper end of the valve assembly. As a result7 the valve assembly 62 will move ullw~udly in the bore 60d to its open position and thus permit the fluid in the conduit 36 to pass from the passage 60b, through a portion of the bore 60d and to the outlet 20 passage 60c. The fluid then exits the regulator 34 and passes through the conduit 37 to the outlet passage 12b of the safety relief valve 10 (figure 1). It is noted that the ulJwal d movement of the valve a.qs~mhly 62 is limited by the engagement of corresponding shoulders formed on the sleeve 66 and the housing 60 as shown in figure 3.
In operation, when the system fluid pressure is within a predetermined limit, the pistons 16 and 42 of the safety relief valve 10 and the pilot valve 30, respectively, as well as the valve assembly 62 of the regulator 34, stay in their rlorrn~l, closed position shown in figure 2. As a result, the pressure of the control fluid in the conduit 28 is equalized to the pressure of the system 30 fluid in the conduit 32 through the pilot valve housing 30 and, more particularly, through the inlet passage 40a, the groove 40e', the space between the necked-down piston portion 40c and the seal ring 52, the bore 40d, and the passage 40b. Also, the flow of the system fluid through the safety relief . _. ....
CA 022~2874 1998-10-29 W O97141496 PCTrUS97100944 - valve 10, and the flow of the control fluid from the chamber 24 of the safety ~elief valve 10 through the conduit 28 and to the pilot valve 30, are prevented.However, when the system fluid pressure exceeds the predetermined limit, the corresponding force acting on the lower surface of the diaphragm 44 5 by the system fluid in the passage 40a of the pilot valve 30 forces the piston42 upwardly to the position shown in figure 3. In this position, the upper portion of the stem 42d of the piston 42 engages the seal 52 and thus blocks commllnication between the passages 40a and 40b; while the lower end of the stem 42d is above the seal ring 54b to permit flow of the control fluid from thechamber 24 of the safety relief valve 10, through the conduit 28, and to the pilot valve 30. The control fluid thus passes through the bore 40d of the pilot valve 30 and, via the conduit 36, to the inlet passage 60b of the regulator 34.
Immediately after the opening of the piston 42 of the pilot valve 30 in the above m~nner the pressure of the control fluid passing from the chamber 15 24, through the pilot valve and to the regulator 34 is substantially the sameas the system pressure. Therefore, the pressure of the control fluid in the passage 60b acting against the lower end of the valve assembly 62 of the regulator 34 forces the valve assembly upwardly to its open position against the force applied to the upper end of the latter assembly by the system fluid 20 pressure. The control fluid thus passes from the passage 60b, through the lower portion of the open bore 60d, and to the outlet passage 60c for passage, via the conduit 37, to the outlet passage 12b of the safety relief valve 10 for disposal. After a portion of the control fluid evacuates the cha_ber 24 of the safety relief valve 10 and passes through the pilot valve 30 and the regulator 25 34 as described above, the pressure of the control fluid lowers to the extentthat the resulting upwardly-directed force acting on the lower end of the valve ~.qs~mhly 62 becomes apprr-~nm~t~ly equal to, or just less than, the force caused by the system pressure acting on the upper end of the valve assembly.
When this occurs the valve assembly 62 moves back to its closed position of 30 figure 2.
The design is such that the valve ~.~semhly 62 will move back to its - closed position when a predetermined percentage of the control fluid evacuates the chamber 24 in the foregoing m~nn~r. This is achieved by fabric~ting the g CA 022~2874 1998-10-29 W O 97/41496 PCT~US97/00944 - -- valve assembly 62 in a m~nn~r so that the surface area of its upper end is a predetermined percentage of the surface area of its lower end, which percentage corresponds to the percentage of the control fluid that evacuates the chamber 24. More particularly, and by way of ~x~mple only, the design of the valve assembly 62 is such that the surface area of the upper end of the valve assembly 62 is al-ll.,xi~ tely 73% ofthe surface area of its lower end.
Therefore, after opening in the above-described m?~nn~r, the valve assembly 62 will close back when the pressure of the control fluid in the chamber 24 reaches approximPtely 73% of the pressure of the system fluid, which results in minim~l blowdown.
In the meantime, the piston 16 of the safety relief valve 10 responds to the increased system fluid pressure and to the control fluid pressure reduction in the chamber 24 by moving to its open position to relieve the fluid pressure in its inlet passage 12a to its outlet passage 12b. Since the fluid pressure 16 reduction in the chamber 24 is apprn~im~t~ly 27%, the design of the safety relief valve 10 can be such that the piston 16 will open when the fluid pressure reduction is slightly less than this value, for ~mple, appro~im~tely 24%. ACCOLdi11g to a main feature of the present invention, the remAining fluid pressure in the chamber, in effect, resists the upward, opening movement of the piston 24 and thus insures that the opening movement of the piston is modulated and that it will thus open gradually. During this time, the piston 42 of the pilot valve 30 remz~in.~ in its upper, closed position thusisnl~ting the system pressure in the conduit 32 from the control fluid in the conduit 28 and therefore the chamber 24 of the safety relief valve 10.
When the system fluid pressure is reduced to a predetermined value as result of the opening of the safety relief valve 10 in the foregoing m~nn~r, thepistons 16 add 42 move to their closed positions shown in figures 1 and 2, respectively. As a result, flow of the control fluid from the chamber 24 of the safety relief valve, through the pilot valve 30 and to the regulator in the above-described manner is terminated, and the pressure of the control fluid eql7~ with the ~y~leln fluid pressure through the passages 40a, the pilot - valve 30 and the passage 40b as described above.
CA 022~2874 1998-10-29 W O 97/41496 PCTrUS97/00944 . --- As a result of all of the foregoing, the opening of the piston 16 of thesafety relief valve is modulated and thus prevented from opening too quickly.
Thus, the almost inst~nt~neous opening of the piston of the prior art safety relief valves, as described above, is ~.limin~ted. As a result, the amount of 5 fluid discharged from the safety relief valve 10 of the present invention is reduced and the wear and stress on the valve components and the associated flow conduits is ..~ ed. Also, the pistons 16 and 42 of the safety relief valve 10 and the pilot valve 30, respectively, as well as the valve assembly 62 of the regulator do not "~h~t,t~r" Further, the ~.qs~mhly of the present 10 invention is relatively inexpensive and simple in construction and operation.It is understood that several variations may be made in the foregoing without departing from the scope of the invention. li',x~n~ples of these variations are as follows:
1. The branch conduit 32a of the conduit 32 can be elimin~ted to 15 ~limin~te the application of the system fluid pressure on the upper portion of the valve assembly 62 of the regulator 34, and a spring or the like can be used to apply the latter force.
2. The diaphragm 44 can be replaced by another type of fluid pressure responshe device such as a bellows, or the like.
3. One or more of the conduits 28, 32, 36, and 37 can be ~limin~ted and the regulator 34 can be mounted directly on the pilot valve 30 and/or the pilot valve can be mounted on the safety relief valve.
Other modific~tion.q, changes and substitutions are also intended and, in some instances, some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner conqi.qtent with the scope of the invention.
Other modific~tion.q, changes and substitutions are also intended and, in some instances, some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner conqi.qtent with the scope of the invention.
Claims (31)
1. A pilot-controlled safety relief valve assembly comprising:
a safety relief valve comprising:
a housing, a piston movable between an opened and a closed position in a chamber defined in the housing in response to predetermined changes in the system fluid pressure to control the flow of the system fluid through the housing, the chamber containing a control fluid the pressure of which controls the movement of the piston; and a pilot valve comprising;
a body member having a first passage connected to the chamber of the safety relief valve for maintaining a pressure of the control fluid in the chamber, a second passage communicating with the first passage, and a piston movable in the body member between closed and open positions to respectively maintain the control fluid pressure in the first passage and enable the control fluid to pass from the first passage to the second passage; and a regulator connected to the second passage of the pilot valve for receiving the control fluid from the pilot valve and venting a portion of the control fluid, said regulator preventing the remaining control fluid from venting so as to maintain a fluid pressure in the chamber of the safety relief valve to modulate the movement of the piston of the safety relief valve from its closed to its open position.
a safety relief valve comprising:
a housing, a piston movable between an opened and a closed position in a chamber defined in the housing in response to predetermined changes in the system fluid pressure to control the flow of the system fluid through the housing, the chamber containing a control fluid the pressure of which controls the movement of the piston; and a pilot valve comprising;
a body member having a first passage connected to the chamber of the safety relief valve for maintaining a pressure of the control fluid in the chamber, a second passage communicating with the first passage, and a piston movable in the body member between closed and open positions to respectively maintain the control fluid pressure in the first passage and enable the control fluid to pass from the first passage to the second passage; and a regulator connected to the second passage of the pilot valve for receiving the control fluid from the pilot valve and venting a portion of the control fluid, said regulator preventing the remaining control fluid from venting so as to maintain a fluid pressure in the chamber of the safety relief valve to modulate the movement of the piston of the safety relief valve from its closed to its open position.
2. The assembly of claim 1 wherein the regulator reduces the control fluid pressure in the chamber of the safety relief valve to a predetermined percentage of the pressure of the system fluid.
3. The assembly of claim 1 wherein the regulator comprises a housing having an inlet for receiving the control fluid and an outlet for venting the portion of the control fluid, and a piston movable in the housing and normally biased to a closed position preventing the flow of the control fluid from the latter inlet to the latter outlet, the piston being exposed to the control fluid in the regulator housing and being adapted to move in the regulator housing to vent the portion of the control fluid from the latter inletto the latter outlet and close in response to a reduction in the pressure of thecontrol fluid as a result of the venting.
4. The assembly of claim 3 wherein in the piston in the regulator housing is also exposed to the system fluid which biases the latter piston to the closed position.
5. The assembly of claim 1 wherein the pilot valve has a third passage connected to the system fluid and wherein the piston of the pilot valve moves between its closed and open positions in response to variations in the pressure of the system fluid.
6. The assembly of claim 5 wherein the piston of the pilot valve is normally in the closed position and opens in response to the pressure of the system fluid exceeding a predetermined value.
7. In an assembly for relieving the pressure of fluid in a system when the pressure exceeds a predetermined value and including a safety relief valve having a piston movable between an opened and a closed position in a chamber defined in a housing in response to predetermined changes in the system fluid pressure to control the flow of the system fluid through the housing, the chamber containing a control fluid the pressure of which controls the piston movement, wherein the improvement comprises:
a pilot valve comprising;
a body member having a first passage connected to the chamber of the safety relief valve for maintaining a pressure of the control fluid in the chamber, a second passage communicating with the first passage, and a piston movable in the body member between closed and open positions to respectively maintaining the control fluid pressure in the first passage and enable the control fluid to pass from the first passage to the second passage; and a regulator connected to the second passage of the pilot valve for receiving the control fluid from the pilot valve and venting a portion of the control fluid, the regulator preventing the remaining contol fluid from venting so as to maintain a fluid pressure in the chamber of the safety relief valve to modulate the movement of the piston of the safety relief valve from its closed to its open position.
a pilot valve comprising;
a body member having a first passage connected to the chamber of the safety relief valve for maintaining a pressure of the control fluid in the chamber, a second passage communicating with the first passage, and a piston movable in the body member between closed and open positions to respectively maintaining the control fluid pressure in the first passage and enable the control fluid to pass from the first passage to the second passage; and a regulator connected to the second passage of the pilot valve for receiving the control fluid from the pilot valve and venting a portion of the control fluid, the regulator preventing the remaining contol fluid from venting so as to maintain a fluid pressure in the chamber of the safety relief valve to modulate the movement of the piston of the safety relief valve from its closed to its open position.
8. The improvement of claim 7 wherein the regulator reduces the control fluid pressure in the chamber of the safety relief valve to a predetermined percentage of the pressure of the system fluid.
9. The improvement of claim 7 wherein the regulator comprises a housing having an inlet for receiving the control fluid and an outlet for venting the portion of the control fluid, and a piston movable in the housing and normally biased to a closed position preventing the flow of the control fluid from the latter inlet to the latter outlet, the latter piston being exposed to the control fluid in the regulator housing and being adapted to move in the regulator housing to vent the portion of the control fluid from the latter inletto the latter outlet and close in response to a reduction in the pressure of thecontrol fluid as a result of the venting.
10. The improvement of claim 9 wherein in the piston in the regulator housing is also exposed to the system fluid which biases the latter piston to the closed position.
11. The improvement of claim 1 wherein the pilot valve has a third passage connected to the system fluid and wherein the piston of the pilot valve moves between its closed and open positions in response to variations in the pressure of the system fluid.
12. The improvement of claim 11 wherein the piston of the pilot valve is normally in the closed position and opens in response to the pressure of the system fluid exceeding a predetermined value.
13. Apparatus for controlling the opening of a safety relief valve having a chamber containing an control fluid that controls the operation of the valve, the apparatus comprising:
a pilot valve comprising:
a body member having a first passage connected to the chamber of the safety relief valve for maintaining a pressure of the control fluid in the chamber, a second passage communicating with the first passage, and a piston movable in the body member between closed and open positions to respectively maintain the control fluid pressure in the first passage and enable the control fluid to pass from the first passage to the second passage; and a regulator connected to the second passage of the pilot valve for receiving the control fluid from the pilot valve and venting a portion of the control fluid, the regulator preventing the remaining contol fluid from venting so as to maintain a fluid pressure in the chamber of the safety relief valve to modulate the movement of the piston of the safety relief valve from its closed to its open position.
a pilot valve comprising:
a body member having a first passage connected to the chamber of the safety relief valve for maintaining a pressure of the control fluid in the chamber, a second passage communicating with the first passage, and a piston movable in the body member between closed and open positions to respectively maintain the control fluid pressure in the first passage and enable the control fluid to pass from the first passage to the second passage; and a regulator connected to the second passage of the pilot valve for receiving the control fluid from the pilot valve and venting a portion of the control fluid, the regulator preventing the remaining contol fluid from venting so as to maintain a fluid pressure in the chamber of the safety relief valve to modulate the movement of the piston of the safety relief valve from its closed to its open position.
14. The apparatus of claim 13 wherein the regulator reduces the control fluid pressure in the chamber of the safety relief valve to a predetermined percentage of the pressure of the system fluid.
15. The apparatus claim 13 wherein the regulator comprises a housing having an inlet for receiving the control fluid and an outlet for venting the portion of the control fluid, and a piston movable in the housing and normally biased to a closed position preventing the flow of the control fluid from the latter inlet to the latter outlet, the latter piston being exposed to the control fluid in the regulator housing and being adapted to move in the regulator housing to vent the portion of the control fluid from the latter inletto the latter outlet and close in response to a reduction in the pressure of thecontrol fluid as a result of the venting.
16. The apparatus of claim 15 wherein in the piston in the regulator housing is also exposed to the system fluid which biases the latter piston to the closed position.
17. The apparatus of claim 1 wherein the pilot valve has a third passage connected to the system fluid and wherein the piston of the pilot valve moves between its closed and open positions in response to variations in the pressure of the system fluid.
18. The apparatus of claim 17 wherein the piston of the pilot valve is normally in the closed position and opens in response to the pressure of the system fluid exceeding a predetermined value.
19. An assembly for controlling the pressure and flow of two fluids, the assembly comprising:
a body member having a first passage connected to a source of the first fluid, a second passage connected to a source of the second fluid, a third passage, and bore connected to the passages; and a piston movable in the bore of the body member between a first position in which it communicates the first and second passages to equalize the pressures of the first and second fluids and blocks communication between the second and third passages to prevent the flow of the second fluid to the third passage, and a second position in which it blocks communication between the first and second passages and communicates the second and third passages to permit the flow of the second fluid to the third passage.
a body member having a first passage connected to a source of the first fluid, a second passage connected to a source of the second fluid, a third passage, and bore connected to the passages; and a piston movable in the bore of the body member between a first position in which it communicates the first and second passages to equalize the pressures of the first and second fluids and blocks communication between the second and third passages to prevent the flow of the second fluid to the third passage, and a second position in which it blocks communication between the first and second passages and communicates the second and third passages to permit the flow of the second fluid to the third passage.
20. The assembly of claim 19 wherein the piston is exposed to the pressure of the first fluid and is normally in the first position and moves to the second position in response to the pressure of the first fluid exceeding a predetermined value.
21. An assembly for controlling the opening of a safety relief valve exposed to a system fluid pressure and containing a control fluid which controls the opening of the safety relief valve, the assembly comprising a pilotvalve connected to the safety relief valve and adapted to respond to a predetermined pressure of the system fluid for permitting flow of the control fluid, a regulator for receiving the control fluid and for reducing the pressureof the control fluid a predetermined amount, the safety relief valve opening in response to the reduction of the control fluid pressure, the remaining control fluid pressure modulating the opening of the safety relief valve.
22. The assembly of claim 21 wherein the control fluid flows from the safety relief valve, through the pilot valve and to the regulator.
23. The assembly of claim 21 wherein the regulator reduces the control fluid pressure in the chamber of the safety relief valve to a predetermined percentage of the pressure of the system fluid.
24. The assembly of claim 21 wherein the pilot valve comprises a body member having a first passage connected to the chamber of the safety relief valve for maintaining a pressure of the control fluid in the chamber, a second passage communicating with the first passage, and a piston movable in the body member between closed and open positions to respectively maintain the control fluid pressure in the first passage and enable the control fluid to pass from the first passage to the second passage.
25. The assembly of claim 24 wherein the pilot valve has a third passage connected to the system fluid and wherein the piston of the pilot valve moves between its closed and open positions in response to variations in the pressure of the system fluid.
26. The assembly of claim 26 wherein the piston of the pilot valve is normally in the closed position and opens in response to the pressure of the system fluid exceeding a predetermined value.
27. The assembly of claim 21 wherein the regulator comprises a housing having an inlet for receiving the control fluid and an outlet for venting the portion of the control fluid, and a piston movable in the housing and normally biased to a closed position preventing the flow of the control fluid from the latter inlet to the latter outlet, the latter piston being exposed to the control fluid in the regulator housing and being adapted to move in the regulator housing to vent the portion of the control fluid from the latter inletto the latter outlet and close in response to a reduction in the pressure of thecontrol fluid as a result of the venting.
28. The assembly of claim 27 wherein in the piston in the regulator housing is also exposed to the system fluid which biases the latter piston to the closed position.
29. A method for controlling the opening of a safety relief valve exposed to a system fluid pressure and containing a control fluid which controls the opening of the safety relief valve, the method comprising the steps of maintaining the control fluid pressure at a value sufficient to maintain the safety relief valve in its open position, responding to a predetermined pressure of the system fluid for permitting flow of the control fluid from the safety relief valve to reduce the pressure of the control fluid an amount sufficient to allow the safety relief valve to open, and terminating the flow of the control fluid after the pressure reduction of the control fluid to maintain a control fluid pressure in the safety relief valve that modulates the opening of the safety relief valve.
30. The method of claim 29 wherein control fluid pressure in the safety relief valve is reduced to a predetermined percentage of the pressure of the system fluid.
31. The method of claim 29 further comprising the step of venting that portion of the control fluid that flows from the safety relief valve.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/642,024 US5725015A (en) | 1996-03-14 | 1996-04-29 | Pilot-operated safety relief valve assembly |
| US08/642,024 | 1996-04-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2252874A1 true CA2252874A1 (en) | 1997-11-06 |
Family
ID=24574856
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2252874 Abandoned CA2252874A1 (en) | 1996-04-29 | 1997-01-22 | Pilot-operated safety relief valve assembly |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0898739A4 (en) |
| AU (1) | AU710544B2 (en) |
| CA (1) | CA2252874A1 (en) |
| EA (1) | EA001043B1 (en) |
| NZ (1) | NZ331537A (en) |
| WO (1) | WO1997041496A1 (en) |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1132369B (en) * | 1956-10-29 | 1962-06-28 | Johannes Petry | Gas pressure regulator |
| DE1265467B (en) * | 1965-04-05 | 1968-04-04 | Pintsch Bamag Ag | Pilot operated pressure regulator for high pressure gas |
| US3456674A (en) * | 1966-05-20 | 1969-07-22 | Fisher Governor Co | In-line flow,pilot-operated high-pressure gas regulator |
| US4355657A (en) * | 1978-09-18 | 1982-10-26 | Vapor Corporation | Pilot operated relief valve |
| DE2949922C2 (en) * | 1979-12-12 | 1986-08-21 | Mannesmann Rexroth GmbH, 8770 Lohr | Pilot operated pressure reducing valve |
| CN1008130B (en) * | 1989-05-19 | 1990-05-23 | 刘长年 | Multifunctional floating pressure control valve |
| US5396923A (en) * | 1992-10-28 | 1995-03-14 | Allen; Donald M. | Surge relief apparatus and method |
-
1997
- 1997-01-22 NZ NZ331537A patent/NZ331537A/en unknown
- 1997-01-22 AU AU17062/97A patent/AU710544B2/en not_active Ceased
- 1997-01-22 CA CA 2252874 patent/CA2252874A1/en not_active Abandoned
- 1997-01-22 EA EA199800964A patent/EA001043B1/en not_active IP Right Cessation
- 1997-01-22 EP EP97903042A patent/EP0898739A4/en not_active Withdrawn
- 1997-01-22 WO PCT/US1997/000944 patent/WO1997041496A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| WO1997041496A1 (en) | 1997-11-06 |
| EP0898739A4 (en) | 1999-11-17 |
| EA001043B1 (en) | 2000-08-28 |
| NZ331537A (en) | 1999-07-29 |
| EP0898739A1 (en) | 1999-03-03 |
| EA199800964A1 (en) | 1999-04-29 |
| AU1706297A (en) | 1997-11-19 |
| AU710544B2 (en) | 1999-09-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |