HEADER RING

A reciprocating pump includes a casing defining a pumping chamber, a plunger configured to reciprocate in an axial direction within the pumping chamber along a plunger axis, and an annular header ring positioned between the plunger and the casing. The annular header ring is formed solely of a fabric-reinforced rubber.

BACKGROUND

High pressure reciprocating pumps are often used to deliver high pressure fluids during earth drilling operations. A sealing arrangement is provided between a pump casing and a reciprocating plunger to reduce the likelihood of leakage and to protect the plunger from potential damage from any abrasive components that may be contained in the fluid being pumped.

The sealing arrangement can include a header ring, such as the header ring shown in U.S. Pat. No. 9,534,691. The header ring disclosed in some embodiments of the '691 Patent is described as an annular body portion which is primarily made of a homogeneous elastomeric material. Bonded to the homogeneous elastomeric portion of body is an annular layer of a fabric reinforced elastomer, the layer covering the surfaces of a pedestal, a sealing lip, a bead and portions of the forward and rearward portions of the body forming surface.

SUMMARY

The invention provides, in a first embodiment, a reciprocating pump. The reciprocating pump includes a casing defining a pumping chamber, a plunger configured to reciprocate in an axial direction within the pumping chamber along a plunger axis, and an annular header ring positioned between the plunger and the casing. The annular header ring is formed solely of a fabric-reinforced rubber.

The invention provides, in another embodiment, an annular header ring defining a central axis. The annular header ring includes a first axial side, a second axial side opposite the first axial side, a first radial side extending between the first and second axial sides and defining an inside diameter of the annular header ring, and a second radial side extending between the first and second axial sides and defining an outside diameter of the annular header ring. The annular header ring is a body uniformly constructed entirely of a fabric-reinforced rubber.

The invention provides, in yet another embodiment, a method of forming an annular header ring. A rubber material is mixed with a fabric material to form a fabric-reinforced rubber having fabric fibers. The fabric-reinforced rubber is cut into sheets on a bias, turning the fabric fibers to an offset angle. The sheets of the fabric-reinforced rubber are joined, and the rejoined sheets are cut into ribbons. The ribbons are stacked or coiled into a preform. The preform is compressed in a mold chamber of a compression mold.

DETAILED DESCRIPTION

FIG. 1illustrates a reciprocating pump100including a power end102and a fluid end104. The power end102includes a crankshaft that drives a plurality of reciprocating plungers within the fluid end104to pump fluid at high pressure.

FIG. 2is a section view taken through the central or plunger axis210of one of the plungers202. Each of the pumping chambers208of the reciprocating pump100includes a plunger202that reciprocates within a casing206of the fluid end104. With each stroke of the plunger202, low pressure fluid is drawn into the pumping chamber208and high pressure fluid is discharged.

A packing arrangement204is positioned between the casing206and the plunger202to form a seal therebetween. The fluid within the pumping chamber208often contains abrasive material that can damage the packing arrangement204and the plunger202if not sealed properly.

As illustrated inFIG. 3the packing arrangement204is disposed within a packing box322that is formed as part of the casing206of the fluid end104. The packing arrangement204includes a junk ring302, a first support ring304, a header ring306, a first pressure ring308, a second pressure ring310, a second support ring312, a lantern ring314, and a packing nut320.

Before discussing the packing arrangement204in detail it is important to understand the terms “upstream” and “downstream”. Any flow through the packing arrangement204or between the packing arrangement204and the plunger202flows from a high pressure side324of the packing box322to a low pressure side adjacent the packing nut320. Thus, upstream would be in the direction away from the packing nut320while downstream would be in a direction toward the packing nut320.

The junk ring302is positioned within the packing box322adjacent the high pressure end324and is preferably made of a hard material such as steel. The junk ring302is annular in shape with a cylindrical inside surface and a cylindrical outside surface. The junk ring302includes a planar lead surface that abuts a planar surface that defines the high pressure end324of the packing box322. Opposite the planar surface is a male chevron portion that faces toward the low pressure end326of the packing box322.

The first support ring304is annular in shape and includes a cylindrical inner surface that abuts the plunger202and a cylindrical outer surface that abuts the wall of the packing box322. The first support ring304also includes a female chevron portion that faces the high pressure end324and abuts the male chevron portion of the junk ring. A male chevron portion is positioned opposite the female chevron portion and faces toward the low pressure end326. In preferred constructions, the first support ring304is manufactured from a material such as polyether ether ketone (PEEK).

The header ring306is positioned on the low-pressure side of the first support ring304and on the high pressure side of the first pressure ring308. Alternatively, the header ring306may be positioned between the first and second pressure rings308,310. The header ring will be discussed in greater detail with regard toFIG. 4. As a further alternative, as shown inFIGS. 6-7, the header ring may abut directly against the junk ring302or directly against the high pressure end of the packing box322(i.e., the high pressure end of the casing206) without a junk ring302or first support ring304therebetween.

The first pressure ring308is an annular ring that includes a cylindrical inner surface that abuts the plunger202and a cylindrical outer surface that abuts the bore of the packing box322. A high pressure side of the first pressure ring308includes a female chevron portion arranged to receive the male chevron portion of the header ring306. An aperture328is formed in the female chevron portion and provides a relief should the arms of the female chevron portion be forced apart. A male chevron portion, opposite the female portion extends toward the low pressure end326of the packing box322. In preferred constructions, the first pressure ring308is formed from an elastomer impregnated aramid fabric.

The second pressure ring310is identical to the first pressure ring308and the second support ring312is identical to the first support ring304. The second support ring312is positioned on the low pressure side of the second pressure ring310.

The first and second pressure rings308,310are the primary sealing components of the packing arrangement, bearing the brunt of the pressure applied by the high-pressure fluid within the pumping chamber208. Therefore, the pressure rings308,310are stiff or inflexible and lack springiness (relative to the header ring306).

The lantern ring314is an elongated annular ring that includes an inner cylindrical surface that abuts the plunger and an outer cylindrical surface that abuts the surface of the packing box322. The high pressure side of the lantern ring314includes a female chevron portion that is arranged to receive the male chevron portion of the second support ring312. One or more lube oil bores318pass between the inner surface and the outer surface and provide a flow path for lube oil that is delivered to the packing arrangement204via the lube oil passage316. In preferred constructions, the lantern ring314is formed from a metal such as aluminum, bronze, or an aluminum-bronze alloy.

Lube oil can be provided to the packing arrangement204via the lube oil passage316and the lube oil bore318. The lube oil creates a pressure seal that enhances the function of the packing arrangement204while provided lubrication between the plunger202and the packing arrangement204.

The packing nut320threadably engages the casing206and is movable between a first position and a second position in which the packing nut320compresses the lantern ring314against the stack including the second support ring312, the second pressure ring310, the first pressure ring308, the header ring306, the first support ring304, and the junk ring302. Collectively, the components of the packing arrangement204are compressed in the direction of the piston axis by the packing nut320, expanding radially to better contact the outer wall or bore of the packing box322and the outer surface of the plunger202.

As illustrated inFIG. 4the header ring306includes an annular outer surface402sized to abut the surface of the packing box322. An inner surface404defines a minimum inside diameter412that is preferably smaller than the outside diameter of the plunger202to assure solid contact with the plunger202to improve the seal. A first portion of the inner surface404is non-cylindrical and is defined by the revolution of a curved line about the center line of the header ring306. The inner surface404further includes a second portion—an annular step or cutout414, adjacent a high pressure side408of the header ring306. The cutout414may be adjacent to the first portion or may otherwise extend partially into the curved line defined by the first portion.

A low pressure side of the header ring306includes a male chevron portion and a knob portion406extending from the male chevron portion toward the low pressure end326of the packing box322. The knob portion406is sized to be received in the aperture328of the first pressure ring308when the packing arrangement204is assembled.

The high pressure side408of the header ring306includes a surface portion that is shaped to mate with the adjacent surface. As shown inFIGS. 4, 6, and 7, the high pressure side408of the header ring306is relatively flat to mate with the high pressure end of the packing box322or the low pressure side of the junk ring302. Alternatively, as shown inFIG. 3, the high pressure side of the header ring306may include a female chevron portion sized to engage the male chevron portion of the first support ring304.

The header ring306has greater elasticity than the pressure rings308,310to maintain a constant force on the pressure rings308,310when assembled in the packing arrangement204. Specifically, when the packing nut320is threaded to the casing206, the nut320compresses the rings306,308,310. The header ring206provides flexibility to compensate for minor compression fluctuations to maintain a constant axial force on the pressure rings308,310for sealing.

FIG. 10illustrates a header ring306having a modified geometry. Specifically, the header ring includes a radial step or cutout1034between the inner surface404and the axial step414. The step cutout formed by the radial and axial steps1034,414may increase the flexibility of the inner surface404that contacts the plunger202.

The header ring306is formed entirely of a cloth or fabric reinforced elastomeric material, such as a fabric reinforced rubber, and more specifically an aramid reinforced rubber. The annular outer surface402, the inner surface404, the low pressure side including the knob portion406, and the high pressure side408of the header ring306are formed of the fabric reinforce rubber. Further, the area between the aforementioned surfaces402,404,406,408is likewise made of the same fabric reinforced material. In other words, the header ring306is a body uniformly constructed entirely from the fabric reinforced elastomeric material without the presence of other dissimilar materials embedded within the body or forming outer layers of the body. Common trade names for aramid fabrics include Kevlar, Nomex, and Twaron.

To form the fabric reinforced rubber into the header ring306, a rubber material (e.g., hydrogenated nitrile butadiene rubber) is mixed with a fabric. The rubber material may be calendered (i.e., via a calender machine using rollers to smooth and thin the material) with the fabric to specification (e.g., with a 35-75 percent rubber pickup, with a 55-65 percent rubber pickup). The roll of rubber-fabric is then cut into sheets on a bias to turn the fabric fibers to an offset angle. The bias cut sheets are joined back together, and cut into ribbon. That ribbon is then turned on edge and stacked or coiled into the preform, as shown inFIG. 5.

Alternatively, the reinforced rubber may be formed via a dip coating or solution coating process. In the dip coating process, the rubber material is dissolved in an applicable solvent for the particular rubber chemistry, or is otherwise converted into a liquid or low viscosity flowable state using an organisol or plasticol. The liquid rubber is then applied to the fabric. The fabric may be pulled through the liquid rubber, or alternatively, the liquid may be applied via a spray coat (e.g., using pneumatic spray equipment, airless sprayers, etc.). Further still, the liquid rubber may be applied via a transfer roll mechanism in which the liquid is applied to the roll and the roll contacts with the fabric to transfer the liquid to the fabric. With a transfer roll mechanism, the coat weight is controlled by varying the roll speed relative to the fabric speed. Once the fabric has been coated, it passes into an oven to remove the solvent or gel the rubber into the fabric, thereby producing the solid rubber-fabric composite. The rubber-fabric material is then rolled and cut as described above.

The preform is placed into a mold chamber of a compression mold, such as the mold510shown inFIG. 8. As shown, the compression mold includes three mold components510A,510B,510C that collectively define the mold chamber. Pressure is applied to the mold components510A,510B,510C such that the fabric reinforced rubber is forced into contact with all areas within the mold chamber. As shown inFIG. 9, the fabric reinforced rubber is molded to the finished shape, producing the header ring306. Some flashing may be produced in the molding process, which can be removed via a post-processing step.

Other header rings may be formed of a homogeneous elastomeric material or may include a fabric-reinforced layer covering surfaces of a homogenous elastomeric material. Such header rings lack advantages of the header ring306discussed above. Specifically, a purely elastomeric header ring lacks the strength and wear resistance provided by the fabric reinforcement. Further, coating a homogeneous elastomeric material with a fabric-reinforced layer only provides limited advantages over the bare homogenous elastomeric material core. Specifically, the interface between the coating and the core provides an additional point of failure for the header ring. Further, as the plunger reciprocates against the header ring, the coating applied to the core can shear away from the core as the fibers of the coating that contact the reciprocating plunger are oriented substantially parallel to the axial direction defined by the movement of the plunger.

In contrast to the other header rings described above (i.e., the purely elastomeric header ring and the header ring having a fabric-reinforced coating), the header ring306is formed solely of the fabric-reinforced rubber, such that there is no interface within the header ring306that is parallel to the axial direction at or adjacent to the inner surface404(that contacts the plunger202) of the header ring306. Further the manufacturing processes utilized to form the header ring orient the fibers of the fabric-reinforced material perpendicular to the axial direction (i.e., the direction of travel of the plunger202), thereby increasing the shear strength of the header ring306in the contact region of the inner surface404.

Experimental testing has been conducted to compare the reliability of the fabric-reinforced rubber header ring306described above to an elastomeric header ring having a fabric-reinforced coating. Running at 9500 psi, the fabric-reinforced rubber header ring306experienced a failure rate of 2.5 percent after 144 stages. In comparison, the elastomeric header ring having a fabric-reinforced coating experienced a failure rate of 71.1 percent after the same number of stages. The fabric-reinforced rubber header ring306was tested to have an average life approximately five times greater than the average life of the elastomeric header ring having a fabric-reinforced coating. A second test was conducted at 10,200 psi with a 100 percent failure rate at 35 hours of the elastomeric header ring having a fabric-reinforced coating. The fabric-reinforced rubber header ring306had no failures when the test concluded at 138 hours. Increasing the average life of the header ring decreases downtime of the reciprocating pump100and likewise decreases maintenance work.