Reciprocating pump fluid cylinder sleeve assembly

A reciprocating pump includes a fluid end having a body defining a plunger bore that engages a plunger sleeve with a threaded interface, where the plunger sleeve defines throughbore configured to receive a plunger operatively reciprocating within the plunger bore during operation of the reciprocating pump. A packing assembly including a plurality of stacked annular seals is disposed between the plunger sleeve and the plunger. A packing nut having a threaded profile for engagement with a threaded surface of the plunger bore asserts a load against the packing assembly to ensure a positive engagement with the plunger.

FIELD

The present disclosure relates to positive displacement pumps, and in particular, to a reciprocating pump fluid cylinder sleeve assembly.

BACKGROUND

Hydraulic fracturing (a.k.a. fracking) is a process to obtain hydrocarbons such as natural gas and petroleum by injecting a fracking fluid or slurry at high pressure into a wellbore to create cracks in deep rock formations. The hydraulic fracturing process employs a variety of different types of equipment at the site of the well, including one or more positive displacement pumps, slurry blender, fracturing fluid tanks, high-pressure flow iron (pipe or conduit), wellhead, valves, charge pumps, and trailers upon which some equipment are carried.

Positive displacement pumps are commonly used in oil fields for high pressure hydrocarbon recovery applications, such as injecting the fracking fluid down the wellbore. A positive displacement pump typically has two sections, a power end and a fluid end. The power end includes a crankshaft powered by an engine that drives the plungers. The fluid end of the pump includes cylinders into which the plungers operate to draw fluid into the fluid chamber and then forcibly push out at a high pressure to a discharge manifold, which is in fluid communication with a well head. A seal assembly, also called a packing assembly or stuffing box, disposed in the cylinder chamber of the pump housing is used to prevent leakage of frac fluid from around the plunger during pumping operations.

DETAILED DESCRIPTION

During the operation of a positive displacement pump, the dynamic seal packing around the plunger will often wear out and sometimes fail, causing damage to the sealing surface of the hydraulic fracturing fluid end block. At this point, the fluid end block will need expensive repair or be scrapped. This type of repair is expensive and time-consuming. The solution described herein uses a sacrificial sleeve around the plunger bore to prevent damage to the hydraulic fracturing fluid end block in the case of packing seal failure. The plunger sleeve described herein has a threaded interface with the fluid end block. The present disclosure describes two sealing designs: a rod seal and a face seal. If the packing seal fails and the sacrificial sleeve becomes damaged, the sleeve can be easily removed and a new sleeve installed. The sleeve and seal arrangement provide relatively inexpensive and reliable solutions for remedying washboarding and/or washout of a packing segment of the plunger bore of the pump. The use of the sleeve also increases the longevity of a fluid cylinder of the pump and thereby reduces operating and maintenance costs.

As shown inFIG.1, a positive displacement reciprocating pump100has a power end102operatively coupled to a fluid end104via a plurality of stay rods106. The fluid end104has a fluid end block105that includes a suction manifold108connected to a fluid source that supplies a fracturing fluid that is commonly called a slurry, which is a mixture of water, abrasive proppants (silica sand or ceramic), and corrosive chemical additives. The fluid end104is also coupled to a discharge manifold110that discharges the fluid at high pressure from the pump100into an encased wellbore. The pump100can also be used to inject a cement mixture down the wellbore for cementing operations. The pump100may be freestanding on the ground, mounted to a skid, or mounted to a trailer.

FIG.2is a cross-sectional view of a reciprocating pump100that incorporates a sacrificial plunger bore sleeve200described herein. The pump100includes a power end102operably coupled to a fluid end104having a fluid end block105(also referred herein as fluid end body105). The fluid end block105has a plurality of chambers formed therein, including a plurality of cylinder chambers208(only one shown inFIG.2). Each of the cylinder chambers208is in communication with a suction manifold108and a discharge port210. A suction cover plate209connects to an end of each cylinder chamber208on a rearward side of the fluid-end block105opposite the stay rods106. A suction valve211opens the cylinder chamber108to the suction manifold108during the intake stroke of the pump. A discharge valve212opens the discharge port210of the cylinder chamber208during the discharge stroke.

The fluid end104further includes plungers214that extend through plunger bores215defined in the cylinder chambers208. Each plunger214is adapted to reciprocate within the corresponding cylinder chamber208during operation of the reciprocating pump100. The power end102of the reciprocating pump100includes a crankshaft216that includes one or more crank throws, corresponding to the one or more cylinders206of the fluid end104, and a main shaft. The crank throws are connected to the main shaft and are each offset from the rotational axis of the crankshaft216. The crankshaft216is mechanically coupled to a power source (not shown) via a bull gear218and a pinion220. The bull gear218is attached to the crankshaft216and the pinion220is connected to a power source or motor (not shown). The gear teeth of the bull gear218mesh with the gear teeth of the pinion220, thereby transmitting torque therebetween. The crank throws are each coupled to a respective one of the plungers214via a mechanical linkage222, each of which includes a connecting rod224, a crosshead226, and a pony rod228. Each of the crossheads226is disposed within a corresponding crosshead bore230, within which the crosshead226is adapted to reciprocate. The connecting rods224connect respective ones of the crossheads226to respective ones of the crank throws. Further, the pony rods228connect respective ones of the crossheads226to respective ones of the plungers214.

In operation, the power source or motor (not shown) rotates the shaft of the pinion220, which rotates the pinion gear teeth that engage the bull gear218and the crankshaft216. The crankshaft216rotates the crank throws about the central axis of the main shaft. The crank throws, in turn, are operable to drive the mechanical linkages222, including respective ones of the connecting rods224, the crossheads226, and the pony rods228, causing the crossheads226to reciprocate within the corresponding crosshead bores230. The reciprocating motion of the crossheads226is transferred to respective ones of the plungers214via the pony rods228, causing the plungers214to reciprocate within the corresponding fluid chambers208. As the plungers214reciprocate within the respective fluid chambers208, fluid is allowed into the fluid cylinders206from the suction manifold108and, thereafter, discharged from the fluid cylinders206into the discharge manifold110.

FIG.3is a more detailed partial cross-sectional view of the fluid cylinder showing an embodiment of the plunger sleeve200using a rod seal300(e.g., having an annular body) disposed at the outside diameter of the sleeve. The fluid end of the pump includes a body105having a plunger bore215that includes an inner wall having first and second inner diameter threaded surfaces312and314. The plunger bore215further incorporates a seal assembly302. The seal assembly302, also commonly called a packing, a seal packing, a packing assembly, a packing stack, or stuffing box, is disposed in the cylinder chamber around the plunger214to prevent leakage of frac fluid from around the plunger during pumping operations. The packing assembly302includes multiple individual annular metallic and/or elastomer seal components (e.g., junk ring, header ring, pressure ring, adapter ring, spacer ring) inserted into a stuffing box successively to form the seal packing during installation. This seal stack is energized by a packing nut304that is also installed in machined contours and an inner diameter threaded surface314defined in the fluid end body105. The packing nut304preloads the seal stack to ensure positive engagement with the plunger214. To remedy washboarding and/or washout of the inner wall of the plunger bore215, the fluid cylinder incorporates a plunger sleeve200(e.g., having a tubular or annular body) disposed between the packing assembly302and the inner wall of the plunger bore215of the fluid cylinder. The plunger sleeve200may be fabricated from a hard durable material or having a coating selected from the group consisting of steel, a tungsten carbide composite, a non-ferrous metal, and a non-metallic composite material now known or later to be developed.

The plunger sleeve200includes a throughbore316that accommodates the plunger214as it reciprocates during operations of the reciprocating pump100. The plunger sleeve200includes an outer diameter surface that incorporates a threaded profile306configured to engage the threaded surface312formed in the fluid end block105. The threaded interface defined between the sleeve200and the block may employ any standard thread profile. Alternatively, a modified stub ACME thread with a rounded or larger root radius may be used. The plunger sleeve200includes an inner wall that defines the throughbore316and the packing assembly302is received within the throughbore316of the sleeve such that the packing extends radially between an exterior surface of the plunger214and the inner wall of the plunger sleeve200. The packing302seals the radial gap defined between the plunger214and the inner wall of the plunger sleeve200to facilitate sealing the plunger214within the plunger bore of the fluid cylinder.

As shown inFIGS.3-5, the plunger sleeve200includes a step308that defines first and second segments of the plunger sleeve200. A first segment of the plunger sleeve200defined on a first side of the step308(e.g., disposed inside the rod seal300) may have a thinner wall, compared to an adjacent, or adjoining, second segment of the plunger sleeve200defined on a second side of the step308. An outer diameter of the first segment may be less than an outer diameter of the second segment. The rod seal300is disposed at an outside diameter surface of the plunger sleeve200spaced from the packing assembly302and functions to prevent intrusion of hydraulic fluids if the seal packing302fails. The rod seal300has an inner diameter profile500that is contoured to have higher and lower features to cause sealing against the outside diameter of the plunger sleeve200(FIG.3). The plunger sleeve is omitted fromFIG.5in order to more clearly illustrate the inner diameter profile500.

Referring toFIG.6, the plunger sleeve200further includes a tool engagement structure600configured as a castle feature on one annular end that is designed to interface with a custom installation tool700shown inFIG.7. One end of the cylindrical installation tool700is contoured with equidistant rectangular projections or flanges702that correspond to equidistant rectangular indentations602on the end of the plunger sleeve200. To install the plunger sleeve200, the installation tool700is used to rotate the plunger sleeve200so that the threaded profile306interfaces with the threaded face of the bore. A chain wrench1200, such as that shown inFIG.11, may be used to securely grab and rotate the installation tool700where its castle features702engage or mesh with the indentations602of the plunger sleeve200. Once the plunger sleeve200is advanced to its proper position within the cylinder bore, a plurality of set screws may be advanced radially inward to secure the plunger sleeve200in place via through-holes604in the walls of the plunger sleeve200and prevent further rotation.

It should be noted that the tool engagement interface of the plunger sleeve200and the corresponding face of the custom installation tool700may incorporate alternate profiles that permit the installation tool to grip the plunger sleeve tightly to enable rotation thereof so that it may advance along the threaded interface with the plunger bore during installation, and retreat along the same threaded interface during removal and maintenance. For example, the alternate tool engagement profile may utilize triangular teeth or engagement features of other suitable shapes.

FIGS.8-10provides various views of another embodiment of the plunger sleeve800incorporating an annular face seal802. The plunger sleeve800also includes an outer diameter surface that incorporates a threaded profile804configured to engage a threaded profile801formed in the fluid end block805. The threaded interface804may employ any standard thread profile. Alternatively, a modified stub ACME thread with a rounded or larger root radius may be used. The plunger sleeve800includes an inner wall that defines a throughbore816(or an internal passage) and a packing assembly806is received within the throughbore816of the sleeve such that the packing seal assembly606extends radially between an exterior surface of the plunger810and the inner wall of the sleeve800. The packing assembly606seals the radial gap defined between the plunger810and the inner wall of the sleeve800to facilitate sealing the plunger within the plunger bore of the fluid cylinder. The packing assembly606is disposed in the cylinder chamber around the plunger810to prevent leakage of frac fluid from around the plunger during pumping operations. The packing assembly606includes multiple individual annular metallic and/or elastomer seal components (e.g., junk ring, header ring, pressure ring, adapter ring, spacer ring) inserted into a stuffing box successively to form the seal packing during installation. This seal stack606is energized by a packing nut814that is also installed in machined contours and threaded surface815in the fluid end block805. The packing nut814preloads the seals606to insure its positive energized engagement with the plunger810. The plunger sleeve800may further incorporate a step808that defines first and second segments of the plunger sleeve800. A first segment of the plunger sleeve800defined on a first side the step808may have a thinner wall, compared to an adjacent or adjoining second segment of the plunger sleeve800defined on a second side of the step808. An outer diameter of the first segment may be less than an outer diameter of the second segment.

As shown inFIGS.8and9, the plunger sleeve800incorporates an annular groove812at the inward facing end in which the annular face seal802is disposed. The annular face seal802is disposed at the end face of the plunger sleeve800spaced from the packing assembly606and functions to prevent the intrusion of hydraulic fluids if the seal packing606fails. As shown inFIG.10, the annular face seal802may feature a keyhole groove900facing toward an inner diameter thereof. A metal energizer ring (not shown) may be used with the annular face seal802.

Similar to the plunger sleeve200shown inFIG.6, the plunger sleeve800shown inFIG.8also includes a tool engagement profile that may include castle features on one annular end that is designed to interface and engage with the same custom installation tool700shown inFIG.7. One end of the cylindrical installation tool700is contoured with equidistant rectangular flanges that correspond to equidistant rectangular indentations on the end of the plunger sleeve800. To install the plunger sleeve800, the installation tool is used to rotate the sleeve so that its threaded face interfaces with the threaded face of the plunger bore. The same chain wrench, such as that shown inFIG.11, may be used to securely grab and rotate the installation tool700that engages the castle feature end of the plunger sleeve800. Once the plunger sleeve800is advanced to its proper position within the plunger bore, a plurality of set screws may be used to secure the sleeve in place via through-holes in the walls of the sleeve to prevent further rotation.

Certain embodiments of the disclosure provide a fluid cylinder for a fluid end section of a reciprocating pump includes a body having a pressure chamber and a plunger bore that fluidly communicates with the pressure chamber. The plunger bore includes a packing segment configured to hold a packing assembly. The fluid cylinder includes a plunger sleeve received within the seal packing segment of the plunger bore. The interface of the plunger bore and the sleeve includes a threaded interface for securely engaging and retaining the plunger sleeve within the plunger bore. The plunger sleeve is configured to hold the plunger within its throughbore such that the plunger is configured to reciprocate within the plunger bore during operation of the reciprocating pump. The fluid cylinder includes a retention mechanism secured within the plunger bore such that the retention mechanism is configured to retain the sleeve within the packing segment of the plunger bore.

The features of the present invention which are believed to be novel are set forth below with particularity in the appended claims. However, modifications, variations, and changes to the exemplary embodiments described above will be apparent to those skilled in the art, and the plunger sleeve assembly for the packing bore described herein thus encompasses such modifications, variations, and changes and are not limited to the specific embodiments described herein.