Abstract:
A pressure relief valve including a valve seat and a valve seat retainer abutting the valve seat. The valve seat has a central channel whereas the valve seat retainer has a number of peripheral channels. A deformable plug is positioned between the valve seat and the valve seat retainer. The deformable plug has a head abutting the valve seat and normally blocking the central channel and a tail abutting the valve seat retainer at a location between the peripheral channels. The tail deforms upon receiving a predetermined load from the head thereby permitting the head to unblock the central channel and open the pressure relief valve.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to fluid handling apparatus and, in particular, destructible or deformable element controlled valves. 
     BACKGROUND OF THE INVENTION 
     It is difficult to produce oil and gas in an economic manner from low permeability reservoir rocks. Production rates are often boosted by resorting to hydraulic fracturing, a technique that increases rock permeability by opening channels through which hydrocarbons can flow to recovery wells. During hydraulic fracturing, a fluid is pumped into the earth under high pressure where it enters a reservoir rock and fractures it. Proppants are carried in suspension by the fluid into the fractures. When the pressure is released, the fractures partially close on the proppants, leaving channels for oil and gas to flow. 
     Specialized pumps are used to develop the pressures necessary to complete a hydraulic fracturing procedure or “frac job.” These pumps are usually provided with so-called fluid ends within which reciprocating plungers place frac fluids under pressure. On rare occasions, enough proppant can become trapped or captured within a fluid end to block the flow of fluid from it, sometimes leading to catastrophic pump failure. A need exists, therefore, for a product that will prevent the buildup of excessive pressures within the fluid end of a pump in the event of a flow blockage. 
     SUMMARY OF THE INVENTION 
     In light of the problems associated with conventional oilfield pumping equipment, it is a principal object of the present invention to provide a pressure relief valve that can be easily installed in the fluid end of a conventional, high-pressure pump to vent fluids in the event that pressures exceeding a predetermined threshold are reached. The preferred pressure relief valve permits the pressure threshold to be set by a user so as to ensure maximum safety in any operating environment. 
     It is another object of the invention to provide a pressure relief valve of the type described that can be readily sized for installation in fluid ends of numerous makes and models. The pressure relief valve can also be installed and serviced with minimal training and with conventional tools. Should the pressure relief valve ever open to relieve pressures in an abnormal situation, it can be rapidly returned to use with the replacement of an expendable part. 
     It is a further object of the invention to provide a pressure relief valve whose fluid discharge can be directed into an area selected by a user. 
     It is an object of the invention to provide improved elements and arrangements thereof in a pressure relief valve for the purposes described that is lightweight, inexpensive to manufacture, and fully dependable in use. 
     Briefly, the pressure relief valve in accordance with this invention achieves the objects noted above by featuring a cage for positioning within a passageway connecting an area of high pressure with an area of low pressure. The cage includes a valve seat having a central channel open to the area of high pressure and a valve seat retainer abutting the valve seat and having a plurality of peripheral channels open to the area of low pressure. The central channel is normally blocked by the head of a deformable plug positioned within the cage between the valve seat and the valve seat retainer. A hollow, bulbous tail extends from the head and abuts the valve seat retainer. Deformation of the tail moves the head away from the seat thus permitting fluid to move from the area of high pressure through the central and peripheral channels to the area of low pressure. A deflector is carried by the valve seat retainer to direct the flow of fluid from the peripheral channels into the area of low pressure. 
     The foregoing and other objects, features and advantages of the present invention will become readily apparent upon further review of the following detailed description of the preferred embodiment as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be more readily described with reference to the accompanying drawings, in which: 
     FIG. 1 is a cross-sectional view of a fluid end of a pump having a pressure relief valve in accordance with the present invention. 
     FIG. 2 is an enlarged cross-sectional view of the pressure relief valve of FIG.  1 . 
     FIG. 3 is a perspective view of deformable plug forming part of the pressure relief valve. 
     FIG. 4 is a side elevational view taken along line  4 — 4  of FIG.  2 . 
     FIG. 5 is a cross-sectional view taken along line  5 — 5  of FIG.  2 . 
     FIG. 6 is a cross-sectional view taken along line  6 — 6  of FIG.  2 . 
     Similar reference characters denote corresponding features consistently throughout the accompanying drawings. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A pressure relief valve in accordance with the present invention is shown at  10 . Pressure relief valve  10  includes a cage  12  for positioning within a passageway  14  in a fluid end  16  connecting a pumping chamber  18 , i.e., an area of high pressure, with the atmosphere, i.e., an area of low pressure. Cage  12  includes a valve seat  20  and an abutting valve seat retainer  22  that together define an interior cavity  24 . Access to cavity  24  is provided by means of a central channel  26  in valve seat  20  that opens to pumping chamber  18  and by means of a plurality of peripheral channels  28  in valve seat retainer  22  that open to the atmosphere. Central channel  26  is normally blocked by the head  30  of a deformable plug  32  positioned within cavity  24 . A hollow, bulbous tail  34  extends from head  30  and abuts valve seat retainer  22 . Should a preset pressure differential be reached between pumping chamber  18  and the atmosphere, the force exerted on head  30  will cause tail  34  to buckle thereby permitting head  30  to move away from valve seat  20  as shown by broken lines in FIG.  2 . Fluid in pumping chamber  18  is then free to flow through cavity  24 , and channels  26  and  28  to the atmosphere. 
     Valve seat  20  includes a primary cylinder  36  for engaging head  30  of plug  32  and a secondary cylinder  38  for distributing pressure surges generated in pumping chamber  18  evenly across head  30 . As shown, primary cylinder  36  includes an outwardly extending peripheral flange  40  at its inner end for abutting a valve seat deck  42  of corresponding shape in passageway  14  and an inwardly extending peripheral flange  44  at its outer end. A pair of O-rings  46  in primary cylinder  36  adjacent flange  40  ensures a fluid-tight seal within passageway  14 . A circumferential groove  48  in peripheral flange  44 , however, snugly receives head  30  and defines a shoulder  50  spacing the side of head  30  from the side of cavity  24 . 
     Secondary cylinder  38  includes a neck  52  extending outwardly from primary cylinder  36  and a peripheral rim  54  at the free end of neck  52 . Neck  52  has a number of radial openings  56  that permit fluid to readily pass from the interior to the exterior of secondary cylinder  38 . An inwardly beveled surface  58  on peripheral rim  54  directs fluid into the interior of secondary cylinder  38 . 
     Neck  52  is provided with an outer diameter that is less than that of primary cylinder  36  and peripheral rim  54 . This area of reduced diameter permits fluids entering secondary cylinder  38  through its open outer end to be jetted radially away from head  30  with minimal frictional losses thereby ensuring that pressures are not concentrated on any side of head  30  or in any portion of pumping chamber  18 . It is believed, over time, that the application of uneven pressure loads to head  30  could result in fluid leakage around head  30  and through relief valve  10 . Of course, the circulatory action of fluids through and around neck  52  ensures that any solids carried by fluids in pumping chamber  18  will remain in suspension and not become lodged against head  30  thereby impeding its action. 
     Valve seat retainer  22  comprises a major cylinder  60  whose outer end is closed by an integral cap  62 . The exterior of cylinder  60  is threaded so that it may be screwed into a correspondingly threaded portion of passageway  14 . To facilitate the turning of cylinder  60  to remove such from passageway  14  by means of a wrench (not shown), an outwardly projecting, hexagonal fitting  64  is provided to the center of cap  62 . Peripheral channels  28  penetrate cap  62  about hexagonal fitting  64  and place cavity  24  in fluid communication with the atmosphere. To ensure that channels  28  cannot become completely blocked by deformed plug  32  when pressure relief valve  10  is open, channels  28  are as widely spaced as possible from the center of cap  62  and partially penetrate major cylinder  60 . An O-ring  66  in the inner end of major cylinder  60  ensures a fluid-tight seal against valve seat  20 . 
     Deformable plug  32  comprises head  30  and tail  34  integrally formed with, and extending from, head  30 . Head  30  is a disk whose load-bearing surface  68  and reinforcing surface  70  are conical and bulge outwardly from the center of the disk so as to permit fluids to easily flow around head  30  when head  30  is disengaged from valve seat  20 . An O-ring  72  about the periphery of surface  68  of head  30  ensures a fluid-tight seal against valve seat  20  in groove  48 . Tail  34 , however, is a hollow bulb that is open at its free end  74 . The free end  74  of tail  34  normally engages the center of cap  62  of valve seat retainer  22  remote from peripheral channels  28  and presses head  30  into groove  48  of valve seat  20  providing a fluid-tight seal. The diameter and thickness of tail  34  are variable, depending on pressure differential threshold desired for opening pressure relief valve  10 . To reduce weight, a hollow  76  may be formed in the surface  70  of head  30  that opens into tail  34 . 
     Shapes other than open-ended bulbs could be incorporated into tail  34 . Cones, cylinders and rods, to name a few, are all possibilities. Unlike bulbs, however, such were not found to collapse evenly and completely so as to not block peripheral channels  28  in valve seat retainer  22 . Furthermore, such were not found to collapse within the close tolerance ranges required by pressure relief valve  10 . 
     A deflector  78  is carried by valve seat retainer  22  to direct the flow of fluid from peripheral channels  28  when pressure relief valve  10  is open. Deflector  78  includes a bowl  80  having a rim  82  with a height substantially equal to that of hexagonal fitting  64  and a notch  84  formed therein serving as a spray nozzle. Rim  82  is oriented so that it points toward cage  12  and the area of high pressure. 
     A bore  86  in the center of bowl  80  permits the passage of a threaded fastener  88  into a correspondingly sized threaded aperture  90  in hexagonal fitting  64  in valve seat retainer  22 . Not only does fastener  88  releasably secure bowl  80  to cage  12 , but, by selectively loosening and retightening fastener  88 , notch  84  may be oriented within a wide, 360° range about fastener  88 . Thus, fluids emitted from pressure relief valve  10  may be sprayed from notch  84  upwardly, downwardly or laterally as conditions dictate. 
     Although pressure relief valve  10  could be used in conjunction with pressure vessels and equipment of various types, it is anticipated that pressure relief valve  10  would find immediate application within the fluid end  16  of a high-pressure pump. Fluid end  16  includes at least one horizontal passageway  14  for receiving a reciprocating plunger  92  at one of its ends and a pressure relief valve  10  at the other of its ends. A vertical passageway  94  intersects passageway  14  to define pumping chamber  18  at their intersection. Vertical passageway  94  contains a suction valve  96  beneath chamber  18  and a discharge valve  98  above chamber  18 . A suction manifold  100  is attached to the bottom of fluid end  16  to provide a flow of fluid into chamber  18  via suction valve  96 . A discharge passage  102  intersects vertical passage  94  and receives fluid pressurized by plunger  92  via discharge valve  98  and ports such from fluid end  16 . 
     From the foregoing, it will be appreciated that use of pressure relief valve  10  is straightforward. First, pressure relief valve  10  is installed within the fluid end  16  of a pump as shown in FIG.  1  and plunger  92  is caused to reciprocate thereby moving fluid from manifold  100 , through valve  96 , into pumping chamber  18  where the fluid is pressurized, past valve  98 , and from passage  102  where it can be conveyed by suitable conduits (not shown) to a location where needed. A blockage of valve  98  or passage  102  will cause the fluid pressure in pumping chamber  18  to increase. 
     The front surface of the head  30  of plug  32 , being exposed to pumping chamber  18 , will transmit the imparted load to tail  34 . Should the load exceed the yield point of tail  34 , tail  34  will evenly flatten or collapse thereby opening pressure relief valve  10 . Fluid may now pass from pumping chamber  18  through cage  12  and out to the atmosphere. The direction that the fluid is sprayed from pressure relief valve  10  is determined in advance by appropriately adjusting the positioning of the notch  84  in deflector bowl  80 . Of course, the spraying of fluid from valve  10  can be easily detected by the operator who can shut down the associated pump. Catastrophic damage to fluid end  16  is usually avoided if the operator acts with reasonable prudence. 
     Pressure relief valve  10  can be continuously reused. To do so, an operator need only unscrew valve seat retainer  22  from passageway  14  and replace the deformed plug  32  that permitted pressure relief valve  10  to open with a new, undeformed plug  32 . After repositioning valve seat retainer  22  and deflector  78 , fluid end  16  can be reenergized. The process requires only a few minutes to complete after which, provided the blockage that caused pressure relief valve  10  to open is cleared, fluid end  16  can be reenergized. 
     While the invention has been described with a high degree of particularity, it will be appreciated by those skilled in the art that modifications may be made thereto. For example, the configuration of the head  30  of plug  32  can be made either as a flat plate for easy manufacturing or may be made even more streamlined to further enhance the ability of pressure relief valve  10