The present invention relates in general to reciprocating pumps and, in particular, to a packing nut lock for a reciprocating pump and a system for holding a cover in position closing an access port of a pump housing.
In oil field operations, reciprocating pumps are often used for various purposes. Some reciprocating pumps, generally known as “service pumps,” are typically used for operations such as cementing, acidizing, or fracing a well. Typically, these service pumps run for relatively short periods of time, but they operate on a frequent basis. Often they are mounted to a truck or a skid for transport to various well sites. A pump might operate several times a week. In many applications, several pumps are connected in parallel to a single flow line.
High pressure pumps are widely used in the petroleum industry for a variety of field operations relating to oil and gas wells. Such pumps deliver a fluid or slurry, which may carry solid particles (e.g., a sand proppant), at pressures up to 20,000 psi. A common type is a positive displacement pump having one or more plungers reciprocally movable in a corresponding pump chamber. Each chamber has an intake port for receiving fluid, a discharge port for exhaust, and a one-way flow valve in each port for preventing reverse flow. These valves require frequent maintenance. Components of the valves are formed of a material which forms an effective seal, such as polyurethane, but which is incapable of withstanding the erosive environment of the pump chamber for an extended duration. Typically, each valve must be serviced after every period of continuous operation at a well site (e.g., every four to six hours) for replacement of worn components. An access port is provided in a wall of the pump housing, at a location near the valves, so that maintenance personnel can readily reach the valves.
The access port must be securely closed and sealed for proper operation of the pump. A closure device, such as a plug with a circumferential seal, is provided for installation in the access port. A retaining cover is typically secured in the access port behind the closure to thinly hold the closure at its installed position. The retaining cover has external threads and is rotatably received in a threaded portion of the access port. Typically, a worker tightens the retaining cover in the access port to a high torque using a sledge hammer and a tool placed in a cavity of the cover to effect its rotation.
Unfortunately, the retaining cover is subject to inadvertently loosen. The pump experiences substantial vibration during operation at high power settings such that the retaining cover can overcome its initially applied torque and begin to “back out”, or rotate in the access port in a loosening direction. Should the retaining cover continue to loosen, the closure and a quantity of high pressure fluid would be ejected from the pump housing and potentially cause damage or injury. Consequently, safety regulations demand that operators respond to any loosening of the retaining cover by stopping the pump. That degrades efficiency and can necessitate the expense of a back-up pump for continuing a pumping operation while the primary pump is shut down.
A retaining system for securing a closure at an installed position within a bore. The bore is positioned within a portion of a housing. The bore has screw threads along at least a portion of the bore. The closure has an internally threaded hole extending into the closure. The closure, when positioned in the installed position, closes the bore.
The retaining system has a retaining cover for obstructing removal of the closure from the bore. The cover is receivable in the bore in a position generally adjacent to the closure. The cover has external threads that are interengageable with the screw threads of the bore such that the cover is rotatable relative to the housing in a tightening direction for movement of the cover into the bore toward the closure and rotatable in an opposite, loosening direction for movement of the cover out from the bore away from the closure. The cover has a central opening extending therethrough that defines an internal wall along the opening. The cover also has a central axis of rotation.
The retaining system also has a locking member configured for being secured to the cover, the locking member has an outer surface which forms a radial abutment to the opening of the cover, and against rotation of the cover relative to the locking member. The locking member has a central clearance bore located in and extending therethrough. A plurality of apertures are located in and extend through the locking member at intervals surrounding the central clearance bore, each aperture having threads extending along its inner surface. A set screw is positioned within each of the plurality of apertures. Each of the set screws has threads interengageable with the threads of the plurality of apertures to allow for the plurality of set screws to be tightened into engagement with the closure, thereby preventing rotation of the locking member relative to the closure.
A fastener is receivable in the central clearance bore of the locking member and the hole of the closure and has external threads interengageable with the threads of the hole in the closure. The threads of the cover and the threads of the fastener are spiraled in the same direction. The cover is securely threaded into the housing. The locking member is inserted into the central opening of the cover, and the faster is inserted through the central clearance bore of the locking member and threaded into the internally threaded hole of the closure, thereby securing the locking member in abutting contact with the closure. The set screws of the locking member are then engaged with the closure, thereby preventing rotation of the locking member relative to the closure, and thus, preventing rotation of the cover relative to the housing.
A retaining system for securing a packing nut at an installed position within a bore. The bore is located in a portion of a housing and has a central axis. The bore has threads along at least a portion thereof. An elongated member extends axially through the bore and is capable of movement along the axis. Packing is positioned between the inner surface of the bore and the member. The packing nut has a plurality of apertures located in the outer peripheries thereof at an angle transverse to the axis. The packing nut in the installed position has threads engaged with the threads of the bore, thereby retaining the packing between the bore and the member.
The retaining the system has a locking device. The locking device has a substantially cylindrical portion that is adapted to be positioned within at least one of the plurality of apertures of the locking nut, thereby connecting the locking device to the packing nut. A plurality of apertures are located in and extend through the locking device at an angle substantially parallel to the axis when the locking device is connected to the packing nut. A set screw is positioned within each of the plurality of apertures of the locking device. The plurality of set screws have threads interengageable with the threads of the plurality of apertures of the locking device to allow for the plurality of set screws to be tightened into engagement with the housing, thereby preventing rotation of the locking device relative to the housing, and thus, preventing the packing nut from rotating relative to the housing when the locking device is connected to the packing nut.
Referring to
Referring to
Referring to
In one embodiment, a gear 24 is mechanically connected to crankshaft 25 and is rotated by the motor through gears 26 and 24. A connector rod 27 connects to a crosshead 29 through a crosshead pin 31, which holds connector rod 27 longitudinally relative to crosshead 29. Connector rod 27 pivots about crosshead pin 31 as crankshaft 25 rotates with the other end of connector rod 27. Pony rod 33 extends from crosshead 29 in a longitudinally opposite direction from crankshaft 25. Connector rod 27 and crosshead 29 convert rotational movement of crankshaft 25 into longitudinal movement of pony rod 33.
A plunger 35 is connected to pony rod 33 for pumping the fluid passing through cylinder housing 17. Packing 36 surrounds plunger 35. A packing nut 38 is threaded into cylinder housing 17, and acts to maintain packing 36 in the proper position within packing bore 37. A number of holes or apertures 40 (
Plunger 35 reciprocates, or moves longitudinally toward and away from cylinder housing 17, as crankshaft 25 rotates. As plunger 35 moves longitudinally away from cylinder chamber 39, the pressure of the fluid inside chamber 39 decreases, creating a differential pressure across inlet valve 41, which actuates valve 41 and allows and allows the fluid to enter cylinder chamber 39 from fluid inlet 19. The fluid being pumped enters cylinder chamber 39 as plunger 35 continues to move longitudinally away from cylinder housing 17 until the pressure difference between the fluid inside chamber 39 and the fluid in fluid inlet 19 is small enough for inlet valve 41 to actuate its closed position. As plunger 35 begins to move longitudinally towards cylinder housing 17, the pressure on the fluid inside of cylinder chamber 39 begins to increase. Fluid pressure inside cylinder chamber 39 continues to increase as plunger 35 approaches cylinder housing 17 until the differential across outlet valve 43 is large enough to actuate valve 43 and allow the fluid to exit cylinder housing 17 through fluid outlet 21. In one embodiment, fluid is only pumped across one side of plunger 35, therefore reciprocating pump 12 is a single-acting reciprocating pump. As the operation of pump 12 is conventional, it will not be described in further detail. During operation of pump 12, vibration and reciprocating forces from plunger 35 may cause packing nut 38 to loosen or back out. As packing nut 38 backs out, packing 36 is affected, resulting in pressure differentials and leaking of packing bore 37.
Referring to
Referring to
The engagement of set screws 73 with cylinder housing 17 locks packing nut lock 67 to cylinder housing 17, and prevents it from rotating relative to housing 17, thereby also preventing packing nut 38 from rotating relative to housing 17. As a result, packing nut lock 67 prevents packing nut 38 from loosening and backing out. Cable 75 (
Referring now to the drawings and in particular to
Access bore cover or retaining cover 22 (broadly, a “retainer”) has a size and shape corresponding with outer portion 87 of bore 85 and is received in outer portion 87 for holding closure 83 at its installed position. Cover 22 has external threads 99 which are interengageable with the threads of outer portion 87 of bore 85. Cover 22 is rotatable relative to housing 17 about a central axis 101 in a tightening direction toward closure 83 and into housing 17, and in a loosening direction away from closure 83 and out from housing 17. When positioned in bore 85, cover 22 obstructs removal of closure 83 from bore 85. A central opening 103 extends through cover 22 and defines an internal wall. In one embodiment, central opening 103 has a polygonal (e.g., hexagonal) shape.
A locking device designated generally at 105 is provided for preventing inadvertent rotation of cover 22. Locking device 105 comprises a fastener 107 which is received in threaded hole 95 of outer face 93 of closure 83. In one embodiment, fastener 107 is aligned with central axis 101 when secured. Fastener 107 illustrated in
Bolt 107 is inserted through bore 113 of locking member 111 and threaded into hole 95 of closure 83. Bolt 107 is tightened to a suitable torque such that the head of bolt 107 applies substantial force against locking member 111. Set screws 117 are tightened to a suitable force against face 93 of closure 83, and consequently, locking member 111 and closure 83 are firmly secured together. Locking device 105 is compatible with existing pump equipment. Although the locking device of the illustrated embodiment has two parts, it is understood that the locking device may have more or fewer parts without departing from the scope of this invention.
Significantly, threads 99 of cover 22 and threads 109 of fastener 107 are spiraled in the same direction. In one embodiment, cover 22 and its corresponding outer portion 87 of access port 85, and the fastener 107 and its corresponding threaded hole 95 are right-hand threaded. Therefore, the loosening direction for cover 22 and bolt 107 is typically a counter-clockwise rotational direction. The form of threads 99, 109 is conventional and of a suitable standardized type and pitch. It is understood that cover 22 and fastener 107 may be left-hand threaded without departing from the scope of this invention.
In operation, pump 12 may generate vibrations when operating at high power settings which tend to loosen cover 22 in its threaded engagement with access port bore 85. Locking device 105 prevents rotation of cover 22 in the loosening direction. Closure 83 does not rotate relative to housing 17 due to friction between closure 83 and bore 85 and due to the mass of closure 83. Frictional forces also act along the outer surface of closure seal 89. The frictional engagement between set screws 117 and face 93 of closure 83, prevents rotation of locking member 111. The nesting engagement of locking member 111 within central opening 103 of cover 22 prevents locking member 111 and cover 22 from rotating relative to one another. The tendency of cover 22 to loosen has insufficient torque to overcome the frictional engagement of set screws 117 of locking member 111 with face 93 of closure 83, thereby preventing rotation of locking member 111, and thus stopping the rotation of cover 22. Consequently, the need to shut down pump 12 due to a loosening cover is precluded.
The invention has several advantages. By eliminating backing off of the packing nut, necessary pressures are maintained between the plunger. Additionally, the incorporation of the packing nut lock helps to prevent the packing bore from leaking due movement of the packing and the backing off of the packing nut. The suction cover locking device helps to prevent rotation of the suction cover and the withdraw of the plug member from within the access bore.
While the invention has been shown or described in only some of its fauns, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.
This application claims priority to provisional application 61/121,464, filed Dec. 10, 2008.
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