PRESSURE RELIEF VALVE HAVING A NOVEL POPPET SEAL

Abstract: A proportioning relief valve (2) incorporating two novel poppet seal constructions (22, 32). Incorporation of metal reinforced fluorocarbon in a novel U-shaped construction (22) provides a pressure actuated poppet-seat seal. Pressure actuation is maintained for "cracking" and full relief positons of the poppet (16), thereby retaining seal/groove integrity. An alternate deformable poppet seal (32) utilizes a laminated multiple disc construction (38) bonded to both seal groove (36) and poppet (34).

Description: PRESSURE RELIEF VALVE HAVING A NOVEL POPPET SEAL BACKGROUND OF THE INVENTION This invention relates to pressure relief valves, and more particularly, to those utilizing spring loaded poppet closure members wherein the poppet head retains a resilient seal. The invention further pertains in particular to 'poppet-type relief valves wherein relief action in valve discharge is proportional to a predeter- mined overpressure as opposed to the more commonly utilized "pop" or total relief operation. The invention disclosed herein provides pressure relief for fluids, i.e. gases and liquids, at pressures as high as 12,000 psi. Relief valves of this type are utilized to protect pressurized vessels or conduits from frequently occurring overpressures. The "proportional" relief characteristic limits the discharge of overpres- sured product to the minimum required for vessel or conduit protection without releasing excessive amounts of product, either to the atmosphere or capture means. Pressure relief of this type can be characterized as overpressure "regulation". A valve of the proportional relief type is disclosed and claimed in U.S. Patent 4,402,341, incorporated by reference hereto. Presently utilized valves, while providing satisfac¬ tory operation, have substantial limitations, particular¬ ly when operating in the regulating mode, i.e. at product pressures at the relief or "cracking" pressure. Poppet movement at the "cracking" pressure, due to reduced seal forces between the poppet and cooperating seat, results in "dribble" or product leakage. This problem is essen¬ tially overcome in "pop" or total relief valve operation, since poppet design provides for product flow assistance in maintaining a rapid and high poppet lift. However, regulating or proportional type relief valves cannot utilize this technique, resulting in poppet/seat designs wherein excessive product loss and/or reduced valve life is frequently encountered. Presently used proportional relief or regulating type relief valves encounter seal problems due to defor¬ mation of seal material. Seal deformation is essentially due. to the displacement by product pressure of resilient seal material. Seals of this type are pressure actuated below the relief or cracking pressures, thereby providing satisfactory low leakage sealing below the relief set¬ ting. ' However, as the cracking pressure is approached, displacement of the deformable or low strength seal material utilized results in seal damage and/or actual permanent displacement or removal of the seal from its retaining structure, usually on the poppet seal face. The invention disclosed herein overcomes these difficulties in providing a valve structure exhibiting extremely small poppet reset (i.e. poppet reseating) hysteresis or high blowdown pressure. This characteris¬ tic is due to a novel pressure actuated seal utilizing a high strength deformation resistant seal material. In addition, the disclosed seal utilizes product pressure at the cracking level to adjust sealing action, thereby- retaining the seal in its poppet groove without seal damage. Additionally, incorporation of a resilient self- retaining poppet seal provides a pressure relief valve having high blowdown pressure, i.e. small pressure/valve closure differential, in a valve construction demonstrat¬ ing greatly increased poppet seal life. Utilization of an elastomeric seal further provides a pressure relief valve having substantially reduced valve leakage or "dribble" at the relief or cracking pressure level. SUMMARY OF THE INVENTION The invention disclosed herein provides a propor- tional or "regulating" type of pressure relief valve incorporating a poppet and novel poppet seal demonstrat¬ ing a very narrow relief/reset pressure differential. The disclosed poppet seal incorporates a composite elastomeric/spring reinforced seal of known design, uniquely applied to the poppet/seal interface. As applied, the disclosed invention provides a poppet seal providing pressure actuated operation for product pressures below and during "cracking" operation. The novel poppet/seal construction results in pressure actuated seal forces which are automatically shifted from the poppet/seat interface to the poppet/stem interface. This action provides low leakage sealing below the cracking pressure and seal retention during "cracking" of the poppet/seat seal and full relief action. In operation, the invention disclosed demonstrates very low hysteresis or high blowdown pressures typically at relief settings of 3,100 psi, a reset pressure of 3,195 psi. Further, the disclosed valve is adjustable under pressure, and utilizes a sealed calibration spring chamber. This construction greatly reduces product attack on the valve calibration spring, thereby substan¬ tially increasing the reliability of pressure relief settings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the relief valve of the disclosed invention in section, particularly showing the poppet and poppet seal in relation to the poppet seat, and calibrat¬ ing spring assembly. Figure 2 shows a sectional view of the novel seal of the invention, wherein the poppet/seat assembly is below relief or cracking pressure. Particularly shown is the location of the poppet/poppet seat, and seal actuation by product pressure. Figure 2A shows the seat seal of Figure 2, at the relief or "cracking" pressure. Particularly shown is the product pressure and shift of poppet seal forces from engagement with the valve seat to engagement with the poppet stem. Figure 2B shows the seat/seal assembly of Figure 2 in full relief. Particularly shown are product flow paths with seal retaining forces. Figure 3 is an alternate, resilient seal construc¬ tion particularly showing bonded laminations of rein¬ forced fluorosilicon material. DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, there is disclosed a relief valve assembly 2, comprising a valve body 4 having an inlet 6, and outlet 10. Internal of the valve body 4 is a poppet chamber 5, a spring chamber 7, and a retained spring adjusting member , 36. The product inlet and relief outlets 6 and 10, further incorporate product inlet and exhaust orifices 8 and 12, respectively, communicating with the product poppet chamber 5. A valve seat 18 is intermediate the valve inlet orifice 8, and poppet chamber 5. poppet assembly 16 is located in the poppet chamber 5, and mounted for reciprocal motion therein. The poppet assembly 16 comprises a poppet head 17, and a poppet .seal assembly 22. Distal said poppet seal assembly on said poppet head 17 and extending therefrom is a poppet stem 20. Surrounding said poppet stem is a poppet stem guide 26 having a spring retaining end 21. A slideably engaging seal 28 prevents product flow from entering the spring chamber 33. The end 21 abuts the valve pressure calibration spring retainer 32, so as to supply predetermined axial force to the poppet assembly 16, thereby calibrating the valve pressure relief or cracking pressure. The spring ; 30 is held between the retainer 31 and adjuster 32. The spring retainer 31 is a spring adjuster and retainer threadably engaged with the upper end of the valve body 4 by threads 36 located on the relief spring adjuster barrel 34. Forces exerted by spring 30 are adjusted by turning the upper end of the adjuster barrel 34, thereby controlling valve relief pressures through control of forces applied to the upper end of the valve poppet stem 20. Turning now to Figure 2, with occasional reference to said Figure 1, in operation, with the valve poppet in the non-relief position shown in Figure 2, poppet pres¬ sure is applied via inlet passage 8 to the lower poppet effective area 14. As the product pressure increases, approaching the "cracking" or preset relief pressure, product pressure on the area 14 produces forces which approach and effectively exceed the preset force exerted by the spring 34 on the poppet stem 20. Below the cracking pressure, static product pressure acting on the outer and inner radial surfaces 23 and 25 of the poppet seal 22, provide a low leakage seal between the poppet assembly 16 and the valve body seat 18. It should be noted that these seal forces are essentially bidirectionally radial, i.e. the seal lips 23A and 25A are impressed outwardly and inwardly, respectively. The intermediate seal surface 27 is further compressed vertically or parallel to the axis of poppet stem 20. Any residual air or product remaining in the seal space above surface 27 as retained in poppet groove 19 (ref Figure 2A) , is vented through seal passage 29. With particular reference to Figure 2A, as the product, pressure equals preset or cracking value of the spring 3O.,. vertical movement of the poppet assembly 16 interrupts- the* pressure actuated seal between radial seal surface 23A and the valve body seat 18, thereby allowing product flow through the intermediate or relief passage 41. As shown in Figure 2A, static pressure continuing on inner radial surface 25A and the intermediate horizontal seal surface therebetween, retains the seal 22 within the poppet seal groove 19. The seal action described above retains seal 22 during the initial poppet motion at the "cracking" pressure. This operation is in sharp contrast with the action of resilient seals currently in use, wherein the deformable characteristic of the seal material results in removal of the seal from its retaining groove, or the necessity of using pressure relief vents in order to ensure seal retention within its groove. Seal retention at small poppet lifts provides reliable valve operation in "proportional" relief operation. In an alternate construction shown in Figure 3, a seal assembly 32 comprises a multiplicity of laminated layers 34, bonded within the poppet seal groove 36. The individual, essentially .disc-like laminar layers 36 comprise a fabric reinforced fluorosilicon plastic. The laminar construction provides an essentially resilient series of planar seal elements 38, each conforming to the particular seal-seat geometry, providing a low leak valve structure at pressures below "cracking" product pressures. In distinct contrast with presently used deformable and pressure actuated seals, the composite structure disclosed is composed of fabric reinforced fluorosilicon plastic in a laminar molded construction, bonded to the poppet seal retention groove, there is provided a novel fluorosilicon poppet/seat relief valve seal. The above described poppet/seat seal provides an essentially non-product sensitive seal, deformable in nature, heretofore unknown in poppet type relief valves. Thus, there has been provided a proportional or regulating type pressure relief valve of the type utiliz¬ ing a poppet closure member having an integral resilient seal, satisfying the objects and objectives of the disclosed invention. Therefore, I claim:

Claims: 1. In a spring loaded pressure relief valve of the type utilizing an axially displaced poppet closure member, the improvement comprising; a poppet mounted in a valve housing for reciprocal motion therein; a concentric seat in said valve housing; a poppet head on the first end of said poppet; an essentially circular seal retention groove, concentric with said poppet head; a resilient seal in said seal groove having essen¬ tially a U-shaped cross-section; first, second, and third pressure sensitive and sealing surfaces defining said U-shaped seal cross-sec¬ tion; a seat in said housing concentric said poppet and in sealing engagement with said first pressure sensitive surface; an inner radial surface in said groove adjacent said first surface and essentially perpendicular said second surface in sealing engagement with said seal second surface; an inner surface in said groove coaxial of and in sealing engagement with said third surface; wherein vertical movement of said poppet interrupts said seat first sealing surface engagement, retaining said third surface/poppet inner groove radial seal. 2. The relief valve of claim 1 wherein said U-shaped seal further comprises first, second, and third surfaces of preformed fluorocarbon impregnated bronze material. 3. In a pressure relief valve of the type utiliz¬ ing an axially reciprocating poppet engaging an essentially coaxial seat below a predetermined or relief pressure, said poppet incorporating an intermediate, essentially coaxial resilient seal intermediate said poppet and seat, the improvement comprising; a poppet head on said poppet, coaxial said seat; an essentially coaxial seal groove on said poppet head, and located essentially adjacent said seat; a plurality of planar bonded essentially ring-like fabric- reinforced fluorosilicon seals in said groove, said ring-like members having an inner surface and first and second areas on its outer periphery; means bonding said inner surface and first outer area to said groove; means forcing said second surface into sealing engagement with said valve body seat; wherein said second surface provides a deformable seal, and said first surface retains said poppet/seal integrity. 4. A method of manufacturing an operating poppet seal for a proportional acting pressure relief valve having a poppet-like closure member and a cooperating poppet seat, said poppet reciprocating between operation and relief positions comprising the steps of; manufacturing ring-like planar seal elements; stacking a plurality of said elements on said poppet at its closure end; and, bonding said stack to said poppet. 5. The method of claim 4 wherein the step of manufacturing ring-like seal elements further includes the step of utilizing fabric reinforced fluorosilicon sheet material.

Inventors: ROGERS RALPH R, ROGERS, RALPH, R.
Applicants: BRUNSWICK VALVE & CONTROL, BRUNSWICK VALVE & CONTROL, INC.
Application year: 1986
Main classification: F16K17
IPC codes: F16K1, F16K17