Scraper ring assembly

An annular scraper ring assembly for a packing arrangement is disclosed. The annular scraper ring assembly can form a seal with a plunger included in a fluid end of a reciprocating pump and includes two or more rings, including a first ring and a second ring. The first ring is formed from a resilient material configured to form a seal against a plunger included in a fluid end of a reciprocating pump and includes an upstream face and an inner surface. The second ring defines a caroming surface configured to engage the upstream face of the first ring and cam the inner surface inwards when the first ring is compressed against the second ring.

FIELD OF INVENTION

The present invention relates to the field of high pressure reciprocating pumps and, in particular, a sealing arrangement for high pressure reciprocating pumps.

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.

SUMMARY

The present application relates to a scraper ring assembly for a packing arrangement of a high pressure reciprocating pump. The scraper ring assembly may be provided independent of any other elements incorporated in a packing arrangement, and/or incorporated in a reciprocating pump.

More specifically, in accordance with at least one embodiment, the present application is directed to an annular scraper ring assembly for a packing arrangement that can form a seal with a plunger included in a fluid end of a reciprocating pump. The scraper ring assembly includes two or more rings, including a first ring and a second ring. The first ring includes an upstream face and an inner surface and is formed from a resilient material configured to form a seal against a plunger included in a fluid end of a reciprocating pump. The second ring defines a camming surface configured to engage the upstream face of the first ring and cam the inner surface of the first ring inwards when the first ring is compressed against the second ring. Thus, advantageously, when the scraper ring assembly is compressed, the camming will increase the magnitude of sealing forces generating by compressing the first ring against the plunger and/or increase the length of time over which sufficient sealing forces are generated. This may protect downstream components of the packing arrangement, as well as downstream portions of the scraper ring assembly, from debris (i.e., abrasive materials) and extend the lifespan of the packing arrangement.

In at least some embodiments, the resilient material of the first ring comprises at least a resilient elastomeric material. In at least some of these embodiments, the second ring is also formed from the resilient material. Alternatively, the second ring may be formed from a second material with a resiliency that is less than a resiliency of the resilient material. That is, the second ring may be formed from a stiffer or less resilient material than the first ring. Forming the second ring from a stiffer material may extend the lifespan of the second ring as compared to the first ring, which may be important since the second ring is upstream of the first ring and may be exposed to more high pressure fluid and abrasive debris than the first ring (e.g., if the second ring functions like a conventional junk ring). On the other hand, forming the second ring from a resilient material, such as the same material as the first ring may allow the second ring to form a seal against a plunger, such as in combination with the first ring, which may provide seal redundancy that expands the life of the scraper ring assembly.

In at least some embodiments, the annular scraper ring assembly also includes a third ring. The third ring has a planar downstream surface and the second ring has an upstream face disposed opposite the camming surface that is configured to engage the planar downstream face of the third ring. The third ring is formed from a third material with a resiliency that is less than the resiliency of the material used to form the first ring. In such embodiments, the third ring may have a longer lifespan than the first ring or second ring, which may be important since the third ring is upstream of the first and second rings and may be exposed to more high pressure fluid and abrasive debris than the first ring (e.g., if the second ring functions like a conventional junk ring). Moreover, forming the third ring from a stiffer material may provide a surface against which the first and second rings can compress to cause radial expansion of the first ring and/or the second ring.

Still further, in some embodiments, the upstream face of the first ring and the inner surface of the first ring meet at a sharp leading edge and the inner surface defines a tapered section that tapers away from the plunger along a downstream direction so that the first ring is widest at the upstream face. Additionally or alternatively, the annular scraper ring assembly may not include a pedestal. These features, either alone or in combination, eliminate any pockets that might encourage a “nibbling” phenomenon that damages sealing elements (i.e., rings). Additionally, the sharp leading edge and the tapered section may effectively peel debris off the plunger, to protect downstream elements of a packing arrangement from debris.

In accordance with another embodiment, the present application is directed to a packing arrangement for a fluid end of a reciprocating pump. The packing arrangement is installable within a packing box disposed at the fluid end of a reciprocating pump and is arranged to form a seal with a plunger of the reciprocating pump. The packing arrangement includes one or more pressure rings and a scraper ring assembly. The scraper ring is disposed upstream of the one or more pressure rings and may include any combination of the features of the scraper ring assembly described above.

In some embodiments, the packing arrangement may also include a packing nut disposed downstream of the one or more pressure rings. The packing nut may be configured to compress at least the one or more pressure rings and the first ring of the scraper ring assembly to cause radial expansion of at least the one or more pressure rings and the first ring within the packing box. Among other advantages, this may secure the scraper ring in a sealed position that prevents blow-by leakage. Additionally or alternatively, the packing arrangement may include a lantern ring disposed between the one or more pressure rings and the packing nut. The lantern ring defines one or more lube oil bores that allow lubricant to be delivered to an outer surface of the plunger. This oil delivery may ensure that sealing rings (e.g., the first ring) can form a proper seal against a reciprocating plunger.

In accordance with another embodiment, the present application is directed to a reciprocating pump include a casing defining a pumping chamber, a plunger configured to reciprocate in an axial direction within the pumping chamber, and an annular scraper ring assembly that can form a seal with the plunger. The annular scraper ring may include any combination of the features of the scraper ring assembly described above.

DETAILED DESCRIPTION

The following description is not to be taken in a limiting sense but is given solely for the purpose of describing the broad principles of the invention. Embodiments of the invention will be described by way of example, with reference to the above-mentioned drawings showing elements and results according to the present invention.

Generally, the scraper ring assembly presented herein improves upon existing sealing arrangements for high pressure reciprocating pumps by improving sealing forces generated by the sealing arrangement and extending the lifespan of the sealing arrangement. To achieve these improvements, the scraper ring assembly includes a first ring and a second ring, insofar as “first” and “second” herein are used to refer to particular rings of two or more rings included in the scraper ring assembly and are not intended to denote a specific location of the ring in a stack or packing arrangement. The first ring mates with a downstream face of the second ring in a manner that cams the first ring into contact with a plunger to increase sealing or compression forces between the first ring and the plunger.

More specifically, the second ring includes a downstream face with a camming surface while the first ring includes an upstream face configured to mate with the camming surface. Thus, when compressed, the inner surface of the first ring is pushed or urged radially inwards, increasing the magnitude of sealing forces generated against the plunger and/or the length of time that sealing forces are exerted. Consequently, these features help achieve a sufficient seal while also extending the lifespan of the scraper ring assembly (and, thus, the lifespan of the packing).

Additionally, the scraper ring assembly presented herein improves debris control. To improve debris control, at least the first ring of the scraper ring assembly has a sharp, highly compressed leading edge. The sharp leading edge peels debris off the plunger. Meanwhile, the shape of the first ring focuses the largest concentration of seal compression forces at or adjacent the upstream face, forming a strong seal that protects both downstream portions of the first ring and downstream rings from high pressure debris. Collectively, the sharp leading edge of the first ring and the overall shape of the rings included in the scraper ring assembly may replace or eliminate a pedestal so that the scraper ring assembly presented does not include any pockets on or adjacent its upstream face that might encourage a “nibbling” phenomenon that damages sealing elements (i.e., rings).

Now referring toFIG.1for a description of an exemplary embodiment of a reciprocating pump100in which the scraper ring assembly presented herein may be included. The reciprocating pump100includes 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. Generally, the power end102is capable of generating forces sufficient to cause the fluid end104to deliver high pressure fluids to earth drilling operations. For example, the power end102may be configured to support hydraulic fracturing (i.e., fracking) operations, where fracking liquid (e.g., a mixture of water and sand) is injected into rock formations at high pressures to allow natural oil and gas to be extracted from the rock formations.

Often, the reciprocating pump100may be quite large and may, for example, be supported by a semi-tractor truck (“semi”) that can move the reciprocating pump100to and from a well. For example, in some instances, a semi may move the reciprocating pump100off a well when the reciprocating pump100requires maintenance. However, a reciprocating pump100is typically moved off a well only when a replacement pump (and an associated semi) is available to move into place at the well, which may be rare. Thus, often, the reciprocating pump is taken offline at a well and maintenance is performed while the reciprocating pump100remains on the well. If not for this maintenance, the reciprocating pump100could operate continuously to extract natural oil and gas. Consequently, any improvements that extend the lifespan of components of the reciprocating pump100, especially typical “wear” components, and extend the time between maintenance operations (i.e., between downtime) are highly desirable.

FIG.2is a sectional view taken through a 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. Often, the fluid within the pumping chamber208contains abrasive material (i.e., “debris”) that can damage the reciprocating pump100. Thus, a packing arrangement204is positioned between the casing206and the plunger202to form a seal therebetween.

In such a reciprocating pump100, the stroke length of the plunger202may be relatively short and, thus, only a limited amount of axial space is available for the packing arrangement204. That is, due to the small stroke length, gas and oil reciprocating pumps for which the scraper ring assembly presented herein is useful have a constrained linear space for a sealing arrangement. For example, the stroke length may be between approximately six and approximately twelve inches. This often limits the types and sized of components that can be included in packing arrangement204.

For example, conventional packing arrangements for short-stroke pumps have been unable to incorporate wiper seals that are often included in equipment that applies hydraulic loads (e.g., construction equipment), which often have longer stroke lengths that provide more room for sealing elements and/or provide seals against significantly lower pressures. This limits the effectiveness with which conventional packing arrangements may remove or detach debris from a plunger202, which, in turn, limits the effectiveness and/or the lifespan of conventional packing arrangements. In fact, as fracking continues to be deployed in more extreme conditions, the pressure, flow rate, and amount of sand introduced into a well continues to increase by orders of magnitude. This generates more debris that conventional packing arrangements struggle to handle while further emphasizing the need for strong and effective seals in a small axial space.

FIGS.3and4show an example embodiment of a packing arrangement204. InFIG.3, the packing arrangement204is illustrated within a packing box322that is formed as part of the casing206of the fluid end104of reciprocating pump100. Meanwhile, inFIG.4, the packing arrangement204is illustrated independent of the casing206. As is discussed in detail below, when the packing arrangement204is disposed in the casing206, compression of the packing arrangement204causes the packing arrangement204to seal against the casing206and the plunger202. Overall, the packing arrangement204includes scraper ring assembly301, a first pressure ring308, a second pressure ring310, a lantern ring314, and a packing nut320. As is discussed in detail below, the scraper ring assembly301includes at least two rings, which may be referred to herein as first ring306(or scraper ring306) and a second ring302(or junk ring302).

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 side326. Thus, if a first component is described as being “upstream” of a second component, the first component will be closer to the high pressure side324than the second component. Likewise, if a first component is described as being “downstream” of a second component, the first component will be closer to the low pressure side326than the second component.

In the depicted packing arrangement204, the scraper ring assembly301is positioned adjacent the high pressure side324. Specifically, the second ring302is positioned within the packing box322adjacent the high pressure side324and the first ring306is positioned immediately downstream of the second ring302. The features of the first ring306and the second ring302are described in detail below, but regardless, in other embodiments, the scraper ring assembly301need not be adjacent the high pressure side324.

In the depicted embodiment, the remainder of the packing arrangement204is disposed downstream of the scraper ring assembly301. Specifically, in the depicted embodiment, the first pressure ring308is downstream of the scraper ring assembly301, the second pressure ring310is downstream of the first pressure ring308, the lantern ring314is downstream of the second pressure ring310, and the packing nut320is downstream of the lantern ring314. However, in other embodiments, the packing arrangement might include any combination of components arranged in any order. For example, an alternative embodiment might include only one pressure ring, three or more pressure rings, any number of support rings, or any other such rings, and each of these components may have suitable axial dimensions to collectively span the axial distance between the second ring302and the packing nut320(each of which might also have varied dimensions across different embodiments).

Still referring toFIGS.3and4, the first pressure ring308is an annular ring that includes a tapered cylindrical inner surface3082that abuts the plunger202and a tapered cylindrical outer surface3084that abuts the bore of the packing box322. An upstream (high pressure) side3086of the first pressure ring308includes a female chevron portion arranged to receive the male chevron portion of the first ring306included in the scraper ring assembly301. An aperture3088is formed in the female chevron portion and provides a relief space that allows the legs of the female chevron portion to flex inwards in response to compression (e.g., generated by the rigid sides of the bore318and plunger202).

The downstream (low pressure) side3089of the first pressure ring308includes a male chevron portion with an apex that extends toward the low pressure side326of the packing box322. In at least some embodiments, the male chevron portion and the female chevron portion have like dimensions so that the downstream side3089of first pressure ring308matches or mirrors the upstream side3086of the first pressure ring308. However, the downstream side3089need not necessarily match or mirror the upstream side3086.

In the depicted embodiment, the second pressure ring310is identical to the first pressure ring308. However, in other embodiments, the second pressure ring310could have different dimensions as compared to the first pressure ring308. For example, the second pressure ring310could have a different height (insofar as “height” refers to a dimension spanning the flow or axial direction), different upstream chevron shape, different aperture shape, different aperture size, and/or different downstream chevron shape as compared to the first pressure ring308.

Regardless of the dimensions, features, and/or characteristics of pressure rings308and310, pressure rings308and310may be the primary sealing components of the packing arrangement204, bearing the brunt of the pressure applied by the high pressure fluid within the pumping chamber208. Therefore, the pressure rings308,310may be stiff or inflexible and lack springiness, at least as compared to one or more rings included in scraper ring assembly301. For example, in at least some embodiments, the first pressure ring308and the second pressure ring310are formed from an elastomer impregnated aramid fabric, but in other embodiments, one or both of pressure ring308and pressure ring310may be formed from other suitable materials.

The lantern ring314is an elongated annular ring that includes an inner cylindrical surface3142that faces the plunger and an outer cylindrical surface3144that faces the inner surface of the packing box322(seeFIG.4). The upstream (high pressure) side3146of lantern ring314includes a female chevron portion that is arranged to receive the male chevron portion of the second pressure ring310(seeFIG.4). In at least some embodiments, the lantern ring314is formed from a metal such as aluminum, bronze, or an aluminum-bronze alloy. Thus, the lantern ring314may, in at least some embodiments, include sealing elements (e.g., O-rings or annular seals) embedded therein (not labeled). The lantern ring314may also include one or more lube oil bores318that extend between its inner surface3142and its outer surface3144to provide a flow path for lube oil that is delivered to the packing arrangement204via an oil passage316formed in casing206(seeFIG.3). The lube oil creates a pressure seal that enhances the function of the packing arrangement204while also providing lubrication between the plunger202and the packing arrangement204.

As is shown inFIG.3, the packing nut320threadably engages the casing206. The threaded engagement allows the packing nut320to compress the lantern ring314against the second pressure ring310, the first pressure ring308, and the first ring306(which may be referred to collectively as a “stack”). This compression causes the stack to expand radially, towards the outer wall or bore of the packing box322and the outer surface of the plunger202. This radial expansion creates seals between: (1) the stack and the outer wall or bore of the packing box322; and (2) the stack and the outer surface of the plunger202.

Now turning toFIGS.5-7for a description of an example embodiment of a scraper ring assembly301. Generally, the scraper ring assembly presented herein includes rings with geometries specifically designed to form a tight and effective seal against the plunger202over a long lifespan. Specifically, the scraper ring assembly301includes a first ring306configured to mate with a second ring302in a manner that cams or pushes the first ring306into contact in response to axial compression of the first ring306. Additionally, the geometries may be designed to prevent, or at least discourage, debris from being trapped against the scraper ring assembly301and/or grinding against sealing areas of the packing arrangement204. To achieve this, at least the first ring306of the scraper ring assembly301has a geometry configured to scrape debris off a plunger once compressed and sealed thereagainst. Each of these features is addressed in turn below.

However, before turning to the aforementioned features, it is important to understand the compositions of the first ring306(i.e., the scraper ring306) and the second ring302(i.e., the junk ring302). The scraper ring306, or portions thereof may be fabricated from any commonly used resilient materials, such as homogeneous elastomers, filled elastomers, partially fabric reinforced elastomers, and full fabric reinforced elastomers. Suitable resilient elastomeric materials includes, but re not limited to, thermoplastic polyurethane (TPU), thermoplastic copolyester (COPE), ethylene propylene diene monomer (EPDM), highly saturated nitrile rubber (HNBR), reinforced versions of the foregoing materials, such as versions reinforced with fibers or laminations of woven material, as well as combinations of any of the foregoing materials. Forming the first ring306from a resilient material allows the first ring306to expand radially in response to axial compression and form a seal against the plunger and/or the casing of a reciprocal pump.

By comparison, the second ring302(i.e., junk ring302), or portions thereof, may be fabricated from any foregoing materials and/or from metals, metal alloys, and/or plastics. Thus, in at least some embodiments, the second ring302may have a resiliency that is less than the resiliency of the first ring306. Put another way, the first ring306may have a first resiliency and the second ring302may have a second resiliency that is less than the first resiliency, insofar as “resiliency” is used herein to describe stiffness, pliability, and other such characteristics and may be represented by, for example, a durometer measurement. In these embodiments, the second ring302may resist axial forces generated by compression of the first ring306against the second ring302(e.g., when the scraper ring assembly301is compressed in the upstream direction) so that the axial compression causes the first ring306to expand radially.

As a specific example, the first ring306may be manufactured from a resilient elastomer and the second ring302may be fabricated from steel, aluminum, bronze, brass, plastic(s) and/or composite plastic(s). Such compositions may be particularly useful when the scraper ring assembly301is immediately adjacent the upstream side324of a packing box322(e.g., abutting a metal casing), as is depicted inFIGS.3-5. In these instances, the second ring302may act similar to a conventional metal junk ring that shrinks the gap between the casing and the plunger upstream of resilient sealing rings.

However, to be clear, for the purposes of this application, the term “junk ring” does not signify that a ring is a metal or metal alloy ring nor does the term “junk ring” require a particular placement in the stack. Instead, “junk ring” is an alternate term used to describe the second ring302of the scraper ring assembly301and is only used because the second ring302may, in some embodiments, perform tasks often performed by a conventional junk ring (among other tasks). In fact, in some embodiments, forming the second ring302from a plastic or plastic composite may provide advantages over traditional metal junk rings. First, manufacturing the second ring302from plastic and/or plastic composite(s) may reduce manufacturing costs as compared to manufacturing from metal. For example, plastics and plastic composites can be molded and quickly mass produced while also avoiding the material costs associated with metal. Second, a plastic or plastic composite ring may be lighter than a metal ring and, thus, may be easier to install in a reciprocating pump. Finally, plastics do not typically have recycling value and thus, will discourage theft for recycling value.

Alternatively, the second ring302may be fabricated from at least the same materials, or similar materials, as the first ring306and may have the same resiliency as or a similar resiliency to the first ring306. In these embodiments, the first ring306and the second ring302may both expand radially in response to axial compression (e.g., when the scraper ring assembly301is compressed in the upstream direction); however, the amount of axial compression of each of ring302and ring306may depend on its resiliency (e.g., on the particular materials and construction used to form the ring). Such compositions may be particularly useful when the scraper ring assembly301includes a third ring and/or is downstream of another ring so that the scraper ring assembly301is not at an upstream end of a stack (and, thus, not immediately adjacent the upstream side324of a packing box322and abutting a metal casing). An example scraper ring assembly301with three rings is depicted inFIGS.8and9and is discussed in details below.

Now turning to the two aforementioned features of the scraper ring assembly301depicted inFIGS.5-7, first, the first ring306(i.e., the scraper ring) includes an upstream face402with a geometry configured to engage a corresponding geometry included on a downstream face510of the second ring302(i.e., the junk ring). In particular, moving from the inner surface504of the second ring302to the exterior surface506of the second ring302, the downstream face510includes a planar section512, a skew section513, an arcuate section514, and an exterior section515. Meanwhile, moving from the inner surface404of the first ring306to the exterior surface406of the first ring306, the upstream face402includes a scraping section421, a planar section422, a skew section423, an arcuate section424, and an exterior section425.

The caroming action between the first ring306and the second ring302may be driven largely by arcuate sections424and514, skew sections423and513, and planar sections422and512. These sections are specifically designed to provide enough space for the first ring306to compress and cam during installation, while minimizing any space where debris might be trapped during pump use. For example, arcuate sections424and514may have identical or nearly identical radiuses to form a tight fit and provide a fulcrum point from which the first ring may expand radially in both directions.

Meanwhile, planar section512(of second ring302) may have a width or radial dimension that is larger than the width or radial dimension of planar section422(of first ring306). Additionally or alternatively, the skew section513(of second ring302) may extend away from the planar section512(of second ring302) at an exterior angle θ4that is smaller than an exterior angle θ2at which the skew section423(of first ring306) extends away from the planar section422(of first ring306) (seeFIGS.6-7for reference). As a specific, non-limiting example, the skew section423may extend away from the planar section422in a downstream direction at an exterior angle θ2in the range of approximately 42° to approximately 48°. Meanwhile, as another non-limiting example, the skew section513may extend away from the planar section512in a downstream direction at an exterior angle θ4of approximately 40°.

The longer planar section512of the second ring302may provide a surface along which the planar section422of the first ring306can slide or cam. The smaller exterior angle θ4may provide space into which the first ring306can expand while also creating a ramp that pushes the skew section423of the first ring306radially inwards. This camming urges the scraping section421radially inwards, compressing the scraping section421against a plunger of a reciprocating pump so that the scraping section421forms a seal with the plunger and scrapes debris off the plunger.

These example dimensions and ranges are merely examples and other ranges may also be suitable. For example, in other embodiments, angles θ2and θ4may be any angle over a range of approximately 40° to approximately 50°, approximately 35° to approximately 55° or even approximately 25° to approximately 65°, provided that the combination of angles can cause suitable camming of the scraping section421towards the plunger202of a reciprocating pump100(e.g., provided that that angles θ4is smaller than angle θ2).

The scraping section421of the upstream face402of the first ring306extends radially inwards from the planar section422, beyond the planar section512of the downstream face510of the second ring302, as can be seen inFIG.5. Thus, the scraping section421may seal a gap between the stack and the plunger202of a reciprocating pump100, such as a reduced gap defined by the second ring302. That is, the second ring302may have a radial dimension or width, as measured between its exterior surface506and its inner surface504that closes a portion of a gap between a plunger202and a casing206, while the first ring306may extend beyond this width to close any remaining, smaller gaps downstream of the second ring302.

Moreover, the scraping section421of the upstream face402of the first ring306extends away from the planar section422of the upstream face402in a downstream direction at an angle θ3. Angle θ3is carefully selected so that when the first ring306is axially compressed and expands radially into a plunger of a reciprocating pump, the scraping section421moves into alignment or nearly into alignment with the planar section422. That is, radial expansion into the plunger will create normal forces on the inner surface404that push the scraping section421in an upstream direction. Thus, after compression, the scraping section421may extend away from a plunger at a right angle or nearly a right angle, such as angle in the range of approximately 88° to approximately 92°, approximately 85° to approximately 95°, or approximately 80° to approximately 100°. To achieve this, angle θ3may be an angle in the range of approximately 12° to approximately 18°. However, this is just an example and, in other embodiments, angle θ3may be any angle over a range of approximately 10° to approximately 20°, approximately 8° to approximately 22° or even approximately 5° to approximately 25°, provided that angle θ3encourages the scraping section421to respond to axial compression by forming a near perpendicular surface against a plunger202.

Finally, the exterior section425is sized and positioned to mate with the exterior section515. Both section425and section515may be substantially planar and, thus, may facilitate radial expansion of one of exterior section425and exterior section515with respect to the other. In at least some embodiments, the exterior section515of second ring302may have a radial dimension or width that is slightly smaller than the radial dimension or width of the exterior section425of first ring306. This may ensure that the first ring306can seal against a casing206of a reciprocal pump100and/or may ensure proper tolerance during installation of the first ring306and the second ring302, especially if the second ring302is formed from metal or metal-like materials.

Now referring toFIGS.4-6, the scraper ring assembly301can effectively scrape debris off a plunger202on which it is sealed due, at least in part, to the specific geometry of the inner surface404of the first ring306. As can be seen, the upstream face402of the scraper ring306(i.e., the first ring) defines the largest inwards radial extension of the scraper ring assembly301. Put another way, overall, the upstream face402has a width W (seeFIG.4) that defines the widest or maximum width of the scraper ring306(and of scraper ring assembly301). Then, the inner surface404tapers inwards from the upstream face402so that the scraper ring306does not have or define a pedestal. Additionally, the second ring302includes a flat or planar upstream face502that does not define a pedestal. Thus, when the scraper ring assembly301is used as the first ring of a packing arrangement, it may protect downstream rings, as well as downstream portions of the scraper ring306, without exposing a pedestal to high pressure fluid and debris.

By comparison, many conventional rings that are used as the first ring of a stack have pedestals or steps defined in their upstream faces. In most of these conventional scraper rings with pedestals, the pedestals help ensure that pressure does not act away from the piston to cause “blow-by leakage” that prevents sealing between the first ring and the piston. However, these pedestals also create a pocket of space adjacent the upstream face of the first ring in which debris can be trapped. Then, reciprocation of the plunger may cause this trapped debris to grind against and damage the first ring, accelerating seal wear and eventually leading to seal failure and leakage that requires pump maintenance (and likely down time). This phenomenon is known as “nibbling” and can significantly reduce the lifespan of the first ring.

To address pedestal nibbling, some conventional packing rings have attempted to strengthen the pedestal or adjacent portions of a packing ring. However, such solutions do not eliminate pedestal nibbling; they simply aim to slow the pedestal nibbling. Such solutions may also require expensive materials or manufacturing techniques. In contrast, the rings of the scraper ring assembly presented herein do not include a pedestal and, thus avoid these issues entirely when used as the first ring in a stack. Instead, the first ring306of the scraper ring assembly301presented herein includes an upstream face402that defines the widest or maximum width of the scraper ring306. Meanwhile, the geometry and/or the compression forces provided by the packing nut320may be adequate to prevent blow-by leakage. For example, the camming created by the interface between the first ring306and the second ring302may counteract any pressure that tends to encourage blow-by leakage.

Still referring toFIGS.4-6, in the depicted embodiment, the inner surface404of first ring306has a tapered section410that tapers away from the plunger202along a downstream direction, thereby ensuring that the scraper ring is widest at the upstream face. In particular, the tapered section410extends away from the upstream face402so that it forms a right or acute angle θ1(e.g., less than or approximately equal 90°) with respect to a radial axis (seeFIG.6). Put another way, the tapered section410tapers in a radial direction towards an exterior surface406of the scraper ring306. Angle θ1ensures that the tapered section410tapers away from the plunger202and that a sharp edge420is formed between the inner surface404and the upstream face402, insofar as “sharp” is used herein to describe a corner that may be acute or right from the perspective of the plunger.

In fact, as mentioned above, when the first ring306is compressed, for example by the packing nut320, and expands radially into the plunger202, the scraper section421of the upstream face402may move in an upstream direction so that the edge420is approximately perpendicular to the plunger. That is, edge420may move towards or into axial alignment with planar section422, thereby softening (e.g., decreasing) the angle θ3of the scraping section421until the tapered section410is approximately perpendicular (e.g., forms a angle in the range of approximately 85° to approximately 95°. Consequently, after the first ring306is compressed, the sharp leading edge420may peel or scrape debris off the plunger202, protecting any downstream rings from exposure to this damaging debris.

In view of the foregoing, angle θ1is carefully selected in view of the stiffness of the first ring306and/or the overall dimensions of the first ring306. For example, in the depicted embodiment, the θ1is any angle in the range of approximately 76° to approximately 82°. However, in other embodiments, angle θ1may be any angle over a range of approximately 74° to approximately 80°, approximately 74° to approximately 84°, approximately 72° to approximately 86°, or even approximately 65° to approximately 89°.

Still further, in the depicted embodiment, the tapered section410extends directly from upstream face402. However, in other embodiments, the tapered section410need not extend directly from the upstream face402. Instead, a cylindrical section may be disposed therebetween so that, for example, the scraper ring defines a first section of constant width adjacent the upstream face402and then tapers towards a narrower width as you move downstream. Additionally or alternatively, the inner surface404and/or the taper section410need not have a single linear taper and, in some embodiments, can have multiple slopes or subsections, whether linear, curved (e.g., parabolic), or shaped in any other way. The inner surface404may also include any number of sections. Regardless, the upstream face402can define the maximum width W of the scraper ring306(seeFIG.4).

When the width of the scraper ring306tapers from the upstream face402, the magnitude of normal forces acting against the inner surface404during compression of the scraper ring306(e.g., via tightening packing nut320) will decrease moving in a downstream direction along the tapered section410. Put another way, when compression causes radial expansion of the scraper ring306, the normal forces acting against the radial expansion will have the largest magnitude at the upstream face402of the scraper ring306(and potentially adjacent the upstream face402if a cylindrical section is disposed between the upstream face402and the tapered section410). This concentration of strong sealing forces at the upstream and leading edge420of the scraper ring306creates a barrier that prevents debris from grinding into a sealing area in a middle axial portion of scraper ring306(i.e., a secondary sealing area of the scraper ring306), prolonging seal life.

Still referring toFIGS.4-6, the first ring306also includes an exterior surface406and a downstream face408. In the depicted embodiment, the exterior surface406is orthogonal to the exterior section425of the upstream face402; however, in other embodiments, the exterior surface406may have any shape that is suitable for an exterior of a packing ring, whether now known or developed hereafter. Also, in the depicted embodiment, the downstream face408has a male chevron412with a protrusion416extending from an apex of the male chevron412(seeFIG.5), but in other embodiments, the downstream face408may have any shape that is suitable for a downstream face of a packing ring, whether now known or developed hereafter.

For example, the downstream face408may have any configuration that allows the scraper ring306to mate, interface, couple, seat against, or otherwise be packed with any other desirable packing rings. That said, in the depicted embodiment, the upstream side3086of the first pressure ring308has a female chevron with an aperture3088so the male chevron412and protrusion416included on the downstream face408of the scraper ring may mate appropriately with the remainder of the stack via the first pressure ring308for additional seal redundancy. Moreover, in the depicted embodiment, the downstream face408of the scraper ring is connected to the inner surface404by a radius R1in a range of approximately 0.055 inches to approximately 0.095 inches; however, in other embodiments, radius R1may be any size or this connection may be a sharp corner.

Now turning toFIGS.5and7, as mentioned, the second ring302may include an exterior surface506and an interior surface504that each extend orthogonally with respect to both the upstream face502and the downstream face510(e.g., with respect to the exterior section515and the planar section512, respectively). However, in other embodiments, the exterior surface506may have any shape that is suitable for an exterior of a packing ring, whether now known or developed hereafter, and the interior surface504may have any shape that is suitable for an interior of a packing ring, whether now known or developed hereafter. Likewise, the upstream face502may have any shape that is suitable for an engaging with a high pressure side324of a packing box322and/or an upstream ring, whether now known or developed hereafter. For example, although the depicted upstream face502is planar, the upstream face502could, in other embodiments include or define one or more steps and/or a chevron.

That said, generally, the radial dimensions of the second ring302are primarily selected to reduce the size of the gap between the casing206and the plunger202so that high pressure fluid acts on a smaller annular portion of a ring immediately downstream of the second ring302, such as first ring306. Additionally or alternatively, in some embodiments, the inner surface504and exterior surface506may define radial (i.e., lateral) dimensions that are at least slightly smaller than sealing components of the packing arrangement (e.g., first ring306, first pressure ring308, and second pressure ring310) to ensure that a hard material, if used to form the second ring302, has appropriate clearances within the packing box322.

Now turning toFIGS.8and9, these Figures illustrate a packing arrangement600including a scraper ring assembly601formed in accordance with a second embodiment. This alternative embodiment scraper ring assembly601includes three rings: a first ring606that is substantially similar to the first ring306of scraper ring assembly301; a second ring602that is substantially similar to the second ring302of scraper ring assembly301; and a third ring603disposed upstream of the second ring602.

In this embodiment, the first ring606of scraper ring assembly601may be axially shorter that the first ring306of scraper ring assembly301; however, the lateral and angular dimensions of the first ring606may be substantially similar to corresponding dimensions of the first ring306. For example, in one embodiment, aside from the taper angle θ1, all of the lateral and angular dimensions of rings306and606may be identical between rings306and606. And, the taper angle θ1may only be smaller in first ring606to accommodate the shrinking of the axial length of ring606(as compared to ring306) while the radial width is maintained (as required by trigonometric principles). However, even with this change, taper angle θ1may still fall within the angular ranges discussed above for angle θ1. Thus, for brevity, the description ofFIGS.8and9focuses on the other rings of scraper ring assembly601, or at least on portions of these rings that differ from like portions of like rings included in scraper ring assembly301. However, any description of like numerals included herein should be understood to apply to like components or features ofFIGS.8and9.

Generally, the second ring602of scraper ring assembly601may have an overall appearance that resembles the second ring302of scraper ring assembly301. However, the second ring602may be axially shorter than the second ring302, may have a different inner surface than the second ring302, have different radial dimensions (i.e., a different width), and may have downstream face610with the different dimensions than the downstream face510of the second ring302. The differences in axial length between the first and second rings606,602of scraper ring assembly601and the corresponding rings306,302of scraper ring assembly301allow the scraper ring assembly601to accommodate third ring603in the limited axial space of the packing box322. The latter three differences may allow the second ring602to seal against a plunger and scrape debris therefrom, in combination with the first ring606and/or in lieu of the first ring606. Each of these differences is described in turn below.

First, the second ring602includes a planar upstream face622and an interior surface624that extends away from the planar upstream face622at acute interior angle θ5(e.g., less than 90°). Put another way, the interior surface624tapers in a radial direction towards an exterior surface626of the second ring602. Acute angle θ5ensures that the interior surface624tapers away from the plunger202and that the inner surface624and the upstream face622for a sharp edge620therebetween, insofar as “sharp” is used in the manner defined above with respect to first ring306of scraper ring assembly301. For example, in the depicted embodiment, angle θ5is in the range of approximately 83° to approximately 89°. However, in other embodiments, angle θ5may be any angle over a range of approximately 80° to approximately 89°, approximately 75° to approximately 89°, or even approximately 60° to approximately 89°.

As is discussed in detail above with respect to first ring306of scraper ring assembly301, a sharp leading edge that is followed by an inward taper—so that the leading edge defines the widest portion of a ring—allows a ring formed of resilient elastomer material to create an effective seal and scrape debris of a plunger. Thus, when second ring602is formed of a resilient elastomer material (an option that is discussed in detail above), the interior surface624of second ring602may achieve the same or similar advantages as the interior surfaces of first rings606and306. With such an arrangement, the first ring606may provide redundant or secondary sealing and scraping (e.g., until the second ring602fails) and/or may provide primary sealing and scraping (e.g., in combination with second ring602and/or after failure of the second ring602). Consequently, this arrangement may extend the lifespan of a packing arrangement beyond the lifespan of a packing arrangement with a single sealing/scraping ring (e.g., packing arrangement204).

Second, the radial dimensions of the second ring602—the width or distance between an interior surface624and an exterior surface626—may be larger than the radial dimensions of second ring302. This may allow the second ring602to compress and seal against both a casing206and a plunger202of a reciprocating pump100. The smaller width of second ring302may provide installation clearance for a metal or metal-like (i.e., a less resilient) ring while second ring602may be formed from a more resilient material that can be installed with smaller clearances.

Third, the second ring602may have downstream face610with different dimensions than the downstream face510of the second ring302. That is, although the downstream face610includes a planar section612, a skew section613, an arcuate section614, and an exterior section615that are similar to the planar section512, the skew section513, the arcuate section514, and the exterior section515of second ring302, the sections of second ring602may have different dimensions. For example, since the second ring602includes a tapered interior surface624configured to engage and seal against a plunger202, the planar section612may be longer than planar section512. Additionally, exterior section615may be wider than exterior section515so that the exterior section615can seal and/or deform against a casing206and/or provide structural stability that prevents quick deterioration.

As another example, the skew section613may extend away from the planar section612in a downstream direction at an exterior angle θ6that is larger than the corresponding exterior angle θ4included in the second ring302. For example, in the depicted embodiment, angle θ6is in the range of approximately 47° to approximately 53°. However, in other embodiments, angle θ6need not be larger than angle θ4and may be any angle over a range of approximately 45° to approximately 55°, approximately 40° to approximately 60°, or even approximately 25° to approximately 65°, provided that the angle θ4can facilitate camming of a skew surface included on a corresponding first ring (e.g., skew section423). That is, skew section can extend at any angle θ4that provides space into which the first ring606can expand while still ensuring that the skew section613can still act as a ramp to push the first ring606radially inwards to compress against a plunger202of a reciprocating pump100.

Still referring toFIGS.8and9, but now with an emphasis onFIG.8, in this embodiment, the third ring603may be a ring formed from a metal or metal-like material. For example, the third ring may be formed from steel, aluminum, bronze, brass, plastic(s) and/or composite plastic(s). In some instances, metals may ensure the third ring603lasts at least as long as first ring606and second ring602; however, plastics and/or plastic composites may also achieve such a lifespan while offering the advantages discussed above in connection with second ring302.

The third ring603is also annular in shape with a cylindrical inner surface6032and a cylindrical outside surface6034. Since the third ring603is formed from a metal or metal-like material, the inner surface6032and outer surface6034may have radial (i.e., lateral) dimensions that are at least slightly smaller than the remaining components of the packing arrangement (e.g., first ring606and second ring602). This ensures that the hard material of the third ring603has appropriate clearances for installation into or removal from a packing box. However, the radial dimensions of the third ring603are primarily selected to reduce the size of the gap between a casing206and a plunger202in a reciprocating pump100so that high pressure fluid acts on a smaller annular portion of a ring downstream of the third ring603(e.g., second ring602and/or first ring606).

The third ring603also includes a stepped upstream surface6036(also referred to as a leading surface or lead surface) that can abut a planar surface of a high pressure side of a packing box in which the scraper ring assembly is disposed. In the depicted embodiment, each stepped portion of the leading surface6036(seeFIG.8) is substantially flat or planar. Opposite the upstream surface6036is a substantially flat or planar downstream surface6038. The planar upstream surface622of the second ring602abuts the planar downstream surface6038of the third ring603.

While the invention has been illustrated and described in detail and with reference to specific embodiments thereof, it is nevertheless not intended to be limited to the details shown, since it will be apparent that various modifications and structural changes may be made therein without departing from the scope of the inventions and within the scope and range of equivalents of the claims. In addition, various features from one of the embodiments may be incorporated into another of the embodiments. For example, inner surface sections from one embodiment may be combined with inner surface sections from another embodiment to form a complete inner surface. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure as set forth in the following claims.

Similarly, it is intended that the present invention cover the modifications and variations of this invention that come within the scope of the appended claims and their equivalents. For example, it is to be understood that terms such as “left,” “right,” “top,” “bottom,” “front,” “rear,” “side,” “height,” “length,” “width,” “upper,” “lower,” “interior,” “exterior,” “inner,” “outer” and the like as may be used herein, merely describe points of reference and do not limit the present invention to any particular orientation or configuration. Further, the term “exemplary” is used herein to describe an example or illustration. Any embodiment described herein as exemplary is not to be construed as a preferred or advantageous embodiment, but rather as one example or illustration of a possible embodiment of the invention.

Finally, when used herein, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc. Meanwhile, when used herein, the term “approximately” and terms of its family (such as “approximate”, etc.) should be understood as indicating values very near to those which accompany the aforementioned term. That is to say, a deviation within reasonable limits from an exact value should be accepted, because a skilled person in the art will understand that such a deviation from the values indicated is inevitable due to measurement inaccuracies, etc. The same applies to the terms “about” and “around” and “substantially”. Also, any ranges provided herein should be understood to include their bounds, so that, for example, a range of 80-90 includes both 80 and 90.