FR2613020A1 - SAFETY OR OVERPRESSURE VALVE - Google Patents

Abstract

THIS VALVE INCLUDES A BODY COMPRISING A MAIN PRESSURE TUBING 32 WITH AN EXHAUST TUBING 34, A VALVE SEAT 38 MOUNTED ON THE MAIN TUBING 32, IN THE SAME BODY, A CYLINDRICAL SLEEVE MOUNTED IN THE SAME BODY AS A DELIMIT CHAMBER 42, A PISTON FLOOR WITH A DIFFERENTIAL SURFACE 36 COMPRISING AN EXTREME PART OF REDUCED SECTION A4 INTENDED TO BE SUPPORTED ON THE VALVE SEAT 38 AND AN EXTREME PART WITH A WIDER SURFACE A5 SLIDINGLY IN THE SLEEVE 41 TO BE MOVED COMING INTO THE INSIDE CHAMBER 42, MEANS 39-40 ALLOWING DIRECTION IN CHAMBER 42 FOR PRESSURE P4 FROM MAIN TUBING 32, THIS PRESSURE P4 COMING FROM MAIN TUBING 32 ACTING ON SAME EXTREME WITH A WIDER SECTION A5 OF THE PISTON FLOOR 36 TO FORCE PUSH BACK THE EXTREME PART WITH REDUCED SECTION A4 OF THE PISTON 36 IN SEALING CONTACT WITH THE VALVE SEAT 38 AND MEANS 46- 48 ALLOWING HERMETICALLY TO CLOSE THE CHAMBER 42 TO ISOLATE THE BACK PRESSURE IN THE EXHAUST TUBING 34.

Description

The present invention relates to safety or sur-

  pressure, and more particularly a safety or overpressure valve with pilot and balanced valve, comprising a main valve comprising a stepped piston with differential surface in order to eliminate the need for a backflow prevention device. Safety or pressure relief valves of the piston type with differential surface comprise a main valve piston which comes to bear on a seat to ensure the tightness of a pipe or pressure vessel. This main valve piston is slidably disposed inside a pressure chamber or dome. Pressure from the main pressure manifold is directed through a pilot valve and into the pressure dome. Under normal conditions, the pressure in the dome is equal to the pressure in the main tubing. Since the surface of the piston in the dome is greater than the area circumscribed by the valve seat, the pressure prevailing in the dome keeps the valve piston against this seat as long as the dome pressure is equal to the

main manifold pressure.

  The pilot valve, which is interposed between the main tubing

  cap and dome is used to vent the pressure in the dome when the main manifold pressure reaches a pre-set level. This venting of the pressure in the dome allows the main manifold pressure to force the piston away from the valve seat, thereby putting the main manifold to exhaust in an exhaust manifold. When the main manifold pressure drops to a preset level, the pilot valve is used to pressurize the dome, thereby closing the main valve by pushing the

piston on the valve seat.

  A defect in the conventional design of the safety valve piston is that the surface of the piston on the side

  valve seat exhaust manifold is exposed to a counter

  pressure occurring in the exhaust manifold and which has an action antagonistic to the dome pressure. Since the piston area under the main manifold pressure, increased by the area under the exhaust manifold pressure, is approximately equal to the area of the piston in the dome, an exhaust manifold pressure above the manifold pressure

  main will combine with this main manifold pressure for as-

  to counteract the dome pressure and cause it to rise

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  the piston of on the valve seat, thus allowing the pressure of tu-

  exhaust bulb to escape into the main manifold. In order to prevent this undesirable phenomenon, the safety or pressure relief valves of an earlier design have incorporated a backflow prevention device in order to allow the main valve to remain hermetically closed in

  presence of high exhaust manifold back pressure.

  This backflow preventer is necessary in prior art safety valves, since simply reducing the area of the valve piston subjected to exhaust manifold pressure necessarily increases the area of that valve piston subjected to main manifold pressure. Since this surface of the piston subjected to the main tubing pressure is close to the surface of the piston appearing in the dome, the differential force is reduced to a point where the seal located at the location of the valve seat

flees.

  This is why, in order to reduce the cost and the complexity of

  safety or pressure relief valves with conventional pilot valve, it is

  care of an improved main valve piston to eliminate the need for

  anti-backflow device.

  The subject of the invention is a safety or overpressure valve with a pilot and balanced valve which uses a main valve comprising a stepped piston with differential surface in order to eliminate the need

a backflow prevention device.

  The stepped piston of the present invention comprises an end portion of reduced section intended to be applied in leaktight manner to the valve seat, between the main pressure pipe and the exhaust pipe. An end portion with a larger section of the piston, obtained by staggering, is arranged in a sliding manner inside a pressure chamber or dome. This dome is constituted by a cylindrical cavity delimited by a sleeve and an upper plate fixed to the body of the main valve. The sleeve has a larger bore forming the cavity which contains the larger surface end portion of the piston and a reduced bore for guiding the reduced section end portion of the piston to the valve seat. A seal is placed between this

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  extreme part of reduced piston section and the sleeve at the place of its reduced bore, in order to prevent a back pressure present in the exhaust manifold from acting on the extreme part with larger surface of the piston finding in the dome. When the main valve piston

  is resting on the valve seat, a surface of the piston is

  On the exhaust manifold side of the valve seat is subjected to a counter pressure. This area can however be reduced to practically zero, since the area of the stepped piston subjected to the main tubing pressure at the location of the valve seat always remains smaller than the wider section of the piston subjected to pressure

  of service prevailing in the dome. In this way, the surface of the piston

  back pressure on the exhaust manifold can be reduced significantly without reducing the force holding the piston against

  the valve seat. As a result, the need for a provision is eliminated.

separate backflow preventive.

  The invention more particularly relates to a valve

  safety or overpressure, characterized in that it comprises a body assembled

  sant a main pressure pipe to an exhaust pipe, a valve seat mounted on the main pipe, in said body, a

  cylindrical sleeve mounted in this same body so as to delimit a cham-

  bre, a stepped piston with a differential surface comprising an end part of reduced section intended to bear on the valve seat and an end part with a wider surface slidably disposed in the

  sleeve so as to move back and forth inside said chamber

  bre, means for directing the pressure in the chamber

  from the main tubing, this pressure from the main tubing

  blade acting on said wider section end portion of the stepped piston so as to forcibly push this reduced section end portion of the piston into sealing contact with the valve seat, and means

  allowing the chamber to be hermetically sealed to isolate it from the counter

  pressure in the exhaust manifold.

  The invention has also e. particular subject a safety valve or pressure relief valve pilot allowing to escape into an exhaust manifold an excess of pressure from a main manifold, characterized in that it comprises a body in which is mounted a sleeve cylindrical so as to delimit a chamber, a valve seat mounted in this body between the main pipe and the pipe

  exhaust, a stepped differential surface piston comprising a

  extreme tie with reduced section intended to bear on the seat

  pope and an end portion with a wider section arranged in a sliding manner

  health in the sleeve so that it can move back and forth inside the

  inside the chamber, a pilot valve intended to direct in the chamber

  bre pressure from the main tubing to force the piston into sealing contact with the valve seat, and

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  sealing means arranged between the reduced section end part of the piston and the sleeve so as to isolate the chamber and the wider section end part of the piston to prevent them from being subjected to a

  back pressure prevailing in the exhaust manifold.

  Another subject of the invention is in particular a safety or overpressure valve with pilot valve, intended to exhaust

  in an exhaust manifold an excess of pressure coming from a tubu-

  main lure, characterized in that it comprises a body in which is mounted a cylindrical sleeve so as to delimit a chamber, a valve seat mounted in this body between the main pipe and the exhaust pipe, said sleeve offering a bore wider delimiting the chamber and a reduced bore opening into this chamber, a stepped differential surface piston having an end portion with a larger surface slidably disposed inside the chamber and an end portion with reduced surface extending from sliding way through said

  bore reduced so as to bear on the valve seat, a valve

  eg pilot to direct the pressure in the chamber from the main tubing so as to force the piston back into sealing contact with the valve seat, a first O-ring placed between the reduced bore and the end section reduced piston

  so as to sealingly isolate the chamber from a counter

  pressure in the exhaust manifold, and a second O-ring located between the larger bore and the end section

wide of the piston.

  Other characteristics and advantages of the invention emerge-

  ront of the description which follows, by way of nonlimiting example and in

  look at the attached drawings on which:

  Figure 1 is a vertical sectional view of a safety valve or

  prior art pilot valve pressure, illustrating a main valve piston of conventional design, and

  Figure 2 is a vertical sectional view of a safety valve or

  pilot and balanced valve pressure, illustrating the main valve to

  stepped piston with differential surface according to the invention.

  Figure 1 shows a pilot valve safety or pressure relief valve IU of a conventional design to illustrate the problem.

  which the present invention remedies. This valve 10 comprises a tube

  main lure under pressure 12 which is connected to an enclosure or pipe

  pressure die (not shown). This valve 10 further comprises a manifold 14 for putting pressure on the exhaust and a valve piston 16 which bears on a valve seat 18 so as to isolate

  the main pressure pipe 12 of the exhaust pipe 14.

  The pressure from the main tubing 12 is directed into a pressure sampling pipe 19, through a pilot valve 20 and into a pressure chamber or dome 22. This cup 22 is delimited by a cylindrical sleeve 21, a top plate

  23 and the piston 16. This piston 16 is slidably arranged inside the

  of the sleeve 21. A helical spring 24 or other biasing means

  resilient tation can be placed in the dome 22 so as to push the piston 16 on the valve seat 18. A pressure P2 prevailing in the dome 22 is exerted on an area of area A2 of the piston 16 so as to push this piston 16 on the valve seat 18 in order to achieve a sealed closure. A seal, such as an O-ring 26, is provided for

  isolate the pressure P2 prevailing in the dome 22 relative to the tube

  exhaust lure 14. A main tubing pressure P1 is exerted on a surface area A1 of the piston 16 by opposing the pressure P2 prevailing in the dome 22. Under normal conditions, the pressure P1 prevailing in the main tube 12 is equal to the pressure P2 prevailing in the dome 22. Consequently, as the area A2 is greater than the area A1, the net force applied to the piston 16 forcibly pushes this piston 16 back into shutter support watertight on the valve seat 18. Furthermore, when the pressure P1 increases, the force of the piston 16 on the

  valve seat 18 also grows to maintain a valve closure

waterproof ration.

  When the pressure P1 prevailing in the main pipe 12 exceeds a prefixed limit, the pilot valve 20 operates so as to release the pressure P2 from the dome 22. Once this pressure P2 has been vented from the dome 22, the main tubing pressure P1 acting on the surface area Ai forces the piston 16 to rise from the valve seat 18 so as to put

  the exhaust the main pipe 12 in the exhaust pipe 14.

  When the pressure P1 drops below a preset level, the pilot valve 20 closes so as to increase the pressure in the dome

  22, thus forcibly returning the piston 16 to the valve seat 18.

  With the classic design of a safety or overpressure valve

  pilot valve balanced, shown in Figure 1, an area of area A3 of the piston 16 located on the exhaust manifold side of the valve seat 18 is subjected to any back pressure P3 present in the exhaust manifold 14. This back pressure P3 acting on

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  the area area A3 combines with the pressure Pl acting on the area area A1 in order to oppose the pressure P2 acting on the area area A2 located in the dome 22. Since the area A1 increased by area A3 is approximately equal to area A2, a back pressure P3 greater than the main manifold pressure P1 will force the piston 16 to lift from the valve seat 18, allowing back pressure exhaust P3 to be the subject of an exhaust in the main pipe 12. It is a highly undesirable phenomenon and the safety or pressure relief valves of the type shown in Figure I must therefore include a device separate backflow preventer (so as to allow the piston 16 to remain in contact with the valve seat 18 regardless of the pressure intensity

  P3 present in the exhaust manifold 14.

  The present invention, which eliminates the need for a separate backflow preventer, is illustrated in the form of the relief or pressure relief valve 30 of Figure 2. This valve 30 includes a main pressure manifold 32, an exhaust manifold 34 and a stepped differential surface piston 36 intended to bear on a valve seat 38 so as to isolate this main pipe 32 from this exhaust pipe 34. A pressure P4 prevailing in the main pipe of

  pressure 32 is exerted on an area of area A4 of the piston 36 and is direct

  gée in a pressure sampling pipe 39, through a valve

  eg pilot 40, up to a pressure chamber or dome 42. This

  pole 42 is delimited by a cylindrical sleeve 41, an upper plate

  43 and the piston 36. This piston 36 is slidably arranged inside the

  inside of sleeve 41 which offers a wider bore delimiting the dome

  42 and a reduced bore opening into this dome 42. A helical spring

  44 or other elastic biasing means can be arranged in

  the dome 42 in order to push the piston 36 back onto the valve seat 38.

  A pressure P5 prevailing in the dome 42 is exerted on a surface area A5 of the piston 36 by forcibly pushing this piston 36 in sealed closure on the valve seat 38. A seal, such as an O-ring 46, is provided for hermetically isolating the pressure P5 prevailing in the dome 42 while the piston 36 moves back and forth inside

of the sleeve 41.

  The piston 36 of the present invention provides a detailed design

  differential surface gage comprising an end portion of reduced section which extends through the reduced bore of the sleeve 41 and offers an area of area A4 intended to bear on the valve seat 38, and

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  an end portion with a wider section offering an area A5 entirely contained inside the dome 42. An additional seal 48, which may for example consist of an O-ring, a membrane or a

  bellows seal, is intended to prevent any back pressure

  tuelle P6 present in the exhaust pipe 34 to act on the wider part of the piston 36 which is located in the sleeve 41. Unlike the piston 16 of the safety or overpressure valve 10 of Figure 1, the

  area of area A6 of the stepped piston 36 located on the exhaust manifold side

  The valve seat 38 can be reduced to almost zero. Even with this area A6 reduced to zero, the area A4 remains smaller than the area A5, so that the pressure P5 (which normally is equal to the pressure P4) acting on the surface of area A5 located in the dome 42 provides a net force making it possible to maintain the stepped piston 36 in leaktight support on the valve seat 38. Furthermore, the back pressure P6 can only act on the surface area A6 very small (or zero) to oppose at the pressure P5 prevailing in the dome 42. In this way, the pressure P6 must greatly exceed the pressure of main tubing P4 to force the piston 36 to rise from the valve seat 38. It

  As a result, the stepped differential surface piston 36 prevents any backflow

  pressure element P6 in the main tubing 32, without being

  need a separate backflow preventer.

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Claims (13)

  1. Safety or overpressure valve, characterized in that it comprises a body joining a main pressure pipe (32) to an exhaust pipe (34), a valve seat (38) mounted on the main pipe (32 ), in said body, a cylindrical sleeve (41) mounted in this same body so as to delimit a chamber (42), a stepped differential surface piston (36) comprising an end portion of reduced section (A4) intended to bear on the valve seat (38) and a larger surface end portion (As) slidably disposed in the sleeve (41) so as to move back and forth within   said chamber (42), means (39-40) for directing in the chamber   bre (42) the pressure (P4) coming from the main tubing (32), this pressure P4 coming from the main tubing (32) acting on said wider end section (A5) of the stepped piston (36) so as to forcibly push back the reduced section end part (A4) of the piston (36) in sealing contact with the valve seat (38), and means (4648) allowing the chamber (42) to be hermetically sealed to isolate it   of the back pressure prevailing in the exhaust manifold (34).   2. Valve according to claim 1, characterized in that the area (A4) of the reduced section end portion of the piston (36) located   2D on the exhaust manifold side (34) of the valve seat (38) and   pressure counter-pressure (Ps) prevailing in the   chamber (42) is substantially zero.   3. Valve according to claim 1, characterized in that the sleeve (41) has a wider bore delimiting the chamber (42) and a reduced bore through which the end section of the reduced section extends in sliding fashion (A4) of the piston (36) in order to bear on the valve seat (38).   4. Valve according to claim 3, characterized in that the sealing means (46-48) comprise a first seal (48) disposed   between the reduced section end part (A4) of the piston (36) and the sage reduced from the sleeve (41).   5. Valve according to claim 4, characterized in that the   first seal (48) is constituted by an O-ring.   6. Valve according to claim 4, characterized in that the sealing means (46-48) further comprise a second seal (46) disposed between the wider section end part (A5) of the piston (36) and   the wider bore of the sleeve (41).   7. Valve according to claim 6, characterized in that the   second seal (46) is constituted by an O-ring.   8. Safety valve or overpressure with pilot valve allowing   to allow an excess of pressure to escape into an exhaust pipe (34)   sion from a main pipe (32), characterized in that it comprises a body in which is mounted a cylindrical sleeve (41) so as to delimit a chamber (42), a valve seat (38) mounted in this body between the main pipe (32) and the exhaust pipe (34), a stepped differential surface piston (36) having an end portion of reduced section (A4) intended to bear on the valve seat (3b) and an extreme part with a wider section (As) arranged so   sliding in the sleeve (41) so that it can move back and forth   comes inside the chamber (42), a pilot valve (40) intended to direct in the chamber (42) the pressure (P4) coming from the main tubing (32) so as to force the piston (36) ) in sealing contact with the valve seat (38), and sealing means (46-48) arranged between the reduced section end part (A4) of the piston (36) and the sleeve (41) so isolating the chamber (42) and the wider end section (A5) of the piston (36) to prevent them from being subjected to a back pressure (P6) prevailing in the tubing exhaust (34).   9. Valve according to claim 8, characterized in that the sleeve (41) has a wider bore delimiting the chamber (42) and a reduced bore through which the end section of the reduced section extends in sliding fashion (A4) piston (36) to take   support on the valve seat (38).   10. Valve according to claim 9, characterized in that the sealing means comprise.t an O-ring (48) disposed between the end portion of reduced section (A4) of the piston (36) and the reduced bore of the sleeve ( 41) to provide a tight seal when the piston (36) moves back and forth.   11. Valve according to claim 9, characterized in that it further comprises a second sealing means (46) making it possible to provide a sealed closure between the end portion with a wider section (A5) of the piston (36) and the wider bore of the sleeve (41) when the   piston (36) moves back and forth in this sleeve (41).   12. Valve according to claim 11, characterized in that   the second sealing means (46) consists of an O-ring.   13. Safety valve or overpressure with pilot valve, intended to put the exhaust in an exhaust pipe (34) an excess of 26 1 3020   ) pressure from a main pipe (32), characterized in that it comprises a body in which is mounted a cylindrical sleeve (41) so as to delimit a chamber (42), a valve seat (38) mounted   in this body between the main pipe (32) and the exhaust pipe-   ment (34), said sleeve (41) offering a wider bore delimiting the chamber (42) and a reduced bore opening into this chamber (42), a stepped differential surface piston (36) having an end portion with a wider surface (A5) slidably disposed inside the chamber (42) and a reduced surface end portion (A4) slidably extending through said reduced bore so as to bear on the valve seat (38 ), a pilot valve 40) making it possible to direct the pressure (P4) coming from the main tube (32) in the chamber (42) so as to force the piston (36) into sealing contact with the valve seat (38), a first O-ring (48) disposed between the reduced bore and the reduced section end portion (A4) of the piston (36) so as to seal the chamber (42)   relative to a back pressure (P6) prevailing in the exhaust manifold   pement (34), and a second O-ring (46) disposed between the bore more   wide and the wider section end (A5) of the piston (36).