Patent Application
20210381603
Conventional mechanical seals are employed in a wide variety of environments and settings, such as for example, in mechanical apparatuses, to provide a fluid-tight seal. The mechanical seals are usually positioned about a rotating shaft or rod that is mounted in and protrudes from a stationary mechanical housing.
Split mechanical seals are employed in a wide variety of mechanical apparatuses to provide a pressure-tight and fluid-tight seal. The mechanical seal is usually positioned about a rotating shaft that is mounted in and protruding from stationary equipment. The mechanical seal is usually bolted to the stationary equipment at the shaft exit, thus preventing the loss of pressurized process fluid from the stationary equipment. Conventional split mechanical seals include face-type mechanical seals, which include a pair of seal rings that are concentrically disposed about the shaft and are axially spaced from each other. The seal rings each have sealing faces that are biased into sealing contact with each other. Usually, one seal ring remains stationary while the other seal ring is coupled to the shaft and rotates therewith. The mechanical seal prevents leakage of the pressurized process fluid to the external environment by biasing the seal ring sealing faces into sealing contact with each other. The rotary seal ring is usually mounted in a holder assembly which is disposed in a chamber formed by a gland assembly. The holder assembly can have a pair of holder halves or segments secured together by a screw. Likewise, the gland assembly can have a pair of gland halves or segments that are also secured together by a screw. The seal rings are also often divided into segments, each segment having a pair of sealing faces, thereby resulting in each ring being a split ring that can be mounted about the shaft without the necessity of freeing one end of the shaft.
Prior art split mechanical seals have rotary and stationary components assembled around the shaft and then bolted on to the equipment to be sealed. A rotary seal face is inserted into a rotary metal clamp after the segments are assembled around the shaft. Then, the stationary face segments and gland segments are assembled and the split gland assembly is then bolted to the pump housing. Alternatively, the stationary and rotary sealing components can be preassembled into subassemblies that can then be mounted about the shaft.
Split mechanical seals that come in rotary and stationary halve assemblies (e.g., four sub-assemblies) have the split surfaces of the metal parts, the elastomer gaskets and O-rings, and the primary faces all in line. This significantly increases the difficulty in assuring that all the components are constrained to come back into sealing alignment. For example, as the O-rings are compressed radially inside their grooves, they expand circumferentially with ends protruding, potentially buckling when joined, thereby causing pinching by metal or seal face parts at the location of the split. The conventional method of staggering the splits of the various parts within the rotating or stationary assemblies cannot be utilized as whole sub-assemblies are secured around the shaft and not individual components. This facilitates and speeds up the seal assembly onto the equipment but can result in parts misalignment and subsequent measurable leakage from the joints formed by the sealing components.
The present invention eliminates this problem specifically as it relates to O-rings or other elastomer split components. The present invention is directed to a split mechanical seal that employs an axially movable spring holder plate. The spring holder plate can engage a sealing element, such as an O-ring, associated with a stationary seal ring. In turn, the stationary seal ring can have a sealing face that engages with a sealing face of a rotary seal ring. The rotary seal ring can also have a sealing element, such as an O-ring, associated therewith. The O-rings are initially disposed in an unloaded position, since the O-rings are not being overly compressed in a radial direction such that the O-rings do not expand circumferentially with ends protruding past the end faces of the holder or gland segments. The spring holder plate can be moved axially by tightening selected bolts associated therewith. When moved axially, the spring holder plate contacts and moves the stationary seal ring and the O-ring associated therewith in an axially inboard direction. The stationary seal ring in turn contacts and moves axially inwardly the rotary seal ring, which in turn moves the O-ring associated therewith in the axially inboard direction. The O-rings are thus moved from the unloaded position to a loaded position where the O-rings are compressed in a radial direction.
The present invention is directed to a mechanical seal for mounting to a housing having a shaft comprising a gland assembly configured for mounting to the housing and having a top surface and an inner surface forming a gland mounting region, wherein the top surface of the gland assembly has a plurality of gland fastener holes formed therein; a holder assembly forming a holder chamber and disposed within the gland mounting region; a rotary seal ring disposed within the holder chamber of the holder assembly and having an outer surface; a rotor sealing element disposed about the outer surface of the rotary seal ring; a stationary seal ring disposed within the gland mounting region and having an outer surface; a stator sealing element disposed about the outer surface of the stationary seal ring; an axially movable spring holder plate having a top surface and an opposed bottom surface and a radially inwardly spaced flange portion, wherein the top surface has a plurality of fastener apertures formed therein; a plurality of biasing clip assemblies configured for mounting about the spring holder plate and for mating engagement with the stationary seal ring for coupling the spring holder plate to the stationary seal ring; and a plurality of fasteners for mounting in the fastener apertures and the gland fastener holes and for securing the spring holder plate to the top surface of the gland assembly. Further, the stator sealing element and the rotor sealing element are disposable in a radially uncompressed state in a first unloaded position and wherein the spring holder plate is movable in the axial direction when the plurality of fasteners are tightened so as to move the stator sealing element and the rotor sealing element in the axial direction into a radially compressed state in a second loaded position.
The top surface of the gland assembly has a plurality of spring holes formed therein and a plurality of springs are mounted in the plurality of spring holes. The holder assembly has an inner surface having a holder detent groove formed therein and the rotary seal ring has a rotary detent groove formed in the outer surface thereof. Further, the inner surface of the stationary seal ring has a groove formed therein for coupling to a portion of each of the plurality of biasing clip assemblies and the inner surface of the gland assembly has a lead-in angled surface. When the plurality of fasteners are tightened, the plurality of biasing clip assemblies applies an axially inward force to the stationary seal ring which in turn applies an axial inward force to the rotary seal ring and the plurality of fasteners axially moves the spring holder plate between the first unloaded position and the second loaded position. In the first unloaded position, the stator sealing element is disposed between the lead-in angled surface and the outer surface of the stationary seal ring and the rotor sealing element is disposed in the holder detent groove and the rotary detent groove such that the stator sealing element and the rotor sealing element are disposed in the radially uncompressed state. In the second loaded position, the stator sealing element is moved axially inwardly from the lead-in angled surface by the flange portion of the spring holder plate and is disposed between the inner surface of the gland and the outer surface of the stationary seal ring and the rotor sealing element is displaced from the holder detent groove by the axial inward movement of the rotary seal ring such that the stator sealing element and the rotor sealing element are disposed in the radially compressed state.
According to the present invention, the spring holder plate has a plurality of recesses formed in the top surface and a portion of each of the plurality of biasing clip assemblies seats in a portion of the recesses. Further, the stationary seal ring has a plurality of spaced apart recesses formed in a top surface thereof. Each of the plurality of biasing clip assemblies comprises an inner spring clip having a main body having an inner ridge portion formed at a first end thereof and configured for engaging with a recessed portion formed in the bottom surface of the spring holder plate, and a bent portion formed at a second opposed end and configured for engaging with one of the plurality of recesses formed in the top surface of the stationary seal ring. The biasing clip assemblies also include an outer spring clip having a first end that is sized and configured for mounting on the main body of the inner spring clip and an opposed second end having a bent tab portion sized and configured for engaging with the groove formed in the inner surface of the stationary seal ring.
The spring holder plate has a main body composed of first and second spring holder plate segments and each of the spring holder plate segments has first and second end faces each of which has a surface feature formed thereon. The surface feature of the first end face of the first spring holder plate segment is a protrusion and the surface feature of the second end face of the first spring holder plate segment is an aperture, and the surface feature of the first end face of the second spring holder plate segment is an aperture configured for seating the protrusion on the first end face of the first spring plate holder segment, and the surface feature of the second end face of the second spring holder plate segment is a protrusion configured for seating in the aperture formed in the second face of the first spring holder plate segment. As such, the surface features on aligned and opposed seal faces of the segments when assembled together are complementary to each other. The main body further has a plurality of recesses formed in the top surface thereof.
The present invention is also directed to a method for positioning a plurality of sealing elements in a mechanical seal. The mechanical seal includes a gland assembly configured for mounting to the housing and having a top surface and an inner surface forming a gland mounting region, wherein the top surface of the gland assembly has a plurality of gland fastener holes formed therein; a holder assembly having an inner surface forming a holder chamber and disposed within the gland mounting region; a rotary seal ring disposed within the holder chamber of the holder assembly and having an inner surface and an opposed outer surface; a rotor sealing element disposed about the outer surface of the rotary seal ring; a stationary seal ring disposed within the gland mounting region and having an inner surface and an opposed outer surface; a stator sealing element disposed about the outer surface of the stationary seal ring; an axially movable spring holder plate having a top surface and an opposed bottom surface and a radially inwardly spaced flange portion, wherein the top surface has a plurality of fastener apertures formed therein; a plurality of biasing clip assemblies configured for mounting about the spring holder plate and for mating engagement with the stationary seal ring for coupling the spring holder plate to the stationary seal ring; and a plurality of fasteners for mounting in the fastener apertures and the gland fastener holes and for securing the spring holder plate to the top surface of the gland assembly. The method of the present invention includes, when the plurality of fasteners are tightened, configuring the plurality of biasing clip assemblies to apply an axially inward force to the stationary seal ring which in turn applies an axial inward force to the rotary seal ring, and configuring the spring holder plate to move axially. Specifically, the spring holder plate is moved axially between an unloaded position where the stator sealing element is disposed between a lead-in angled surface formed in the inner surface of the gland assembly and the outer surface of the stationary seal ring and the rotor sealing element is disposed in a holder detent groove formed in the inner surface of the holder assembly and in a rotary detent groove formed in the outer surface of the rotary seal ring, wherein the stator sealing element and the rotor sealing element are in a radially uncompressed state when in the unloaded position, and a loaded position where the stator sealing element is configured to move axially inwardly from the lead-in angled surface by the flange portion of the spring holder plate and is disposed between the inner surface of the gland and the outer surface of the stationary seal ring and the rotor sealing element is configured to be displaced from the holder detent groove by the axial inward movement of the rotary seal ring, wherein the stator sealing element and the rotor sealing element are in a radially compressed state when in the loaded position.
The plurality of biasing clip assemblies comprises an inner spring clip having a main body having an inner ridge portion formed at a first end thereof and configured for engaging with a recessed portion formed in the bottom surface of the spring holder plate, and a bent portion formed at a second opposed end and configured for engaging with one of the plurality of recesses formed in the top surface of the stationary seal ring; and an outer spring clip having a first end that is sized and configured for mounting on the main body of the inner spring clip and an opposed second end having a bent tab portion sized and configured for engaging with the groove formed in the inner surface of the stationary seal ring. The step of configuring the plurality of biasing clip assemblies to apply an axially inward force, when the plurality of fasteners are tightened, includes applying an axial inward force to the stationary seal ring with the inner spring clip by contacting the recess formed in the top surface of the stationary seal ring.
These and other features and advantages of the present invention will be more fully understood by reference to the following detailed description in conjunction with the attached drawings in which like reference numerals refer to like elements through the different views. The drawings illustrate principals of the invention and, although not to scale, show relative dimensions.
The present invention provides a mechanical seal for providing sealing on a rotating shaft or other suitable device. The invention will be described below relative to illustrated embodiments. Those skilled in the art will appreciate that the present invention may be implemented in a number of different applications and embodiments and is not specifically limited in its application to the particular embodiment depicted herein.
The terms “mechanical seal system,” “mechanical seal,” “sealing system” and “sealing assembly” as used herein are intended to include various types of mechanical fluid sealing systems, including single or solid seals, split seals, concentric seals, spiral seals, cartridge seals, and other known mechanical seal and sealing types and configurations.
The term “shaft” is intended to refer to any suitable device in a mechanical system to which a mechanical seal can be mounted and includes shafts, rods and other known devices. The shafts can move in any selected direction, such as for example in a rotary direction or in a reciprocating direction.
The terms “axial” and “axially” as used herein refer to a direction generally parallel to the axis of a shaft. The terms “radial” and “radially” as used herein refer to a direction generally perpendicular to the axis of a shaft. The terms “fluid” and “fluids” refer to liquids, gases, and combinations thereof.
The terms “axially inner” or “axially inboard” as used herein refer to the portion of the stationary equipment and a mechanical seal proximate the stationary equipment employing the mechanical seal. Conversely, the terms “axially outer” or “axially outboard” as used herein refer to the portion of stationary equipment and a seal assembly distal from the mechanical system.
The term “radially inner” as used herein refers to the portion of the mechanical seal proximate a shaft. Conversely, the term “radially outer” as used herein refers to the portion of the mechanical seal distal from a shaft.
The terms “stationary equipment,” “static surface” and “gland” as used herein are intended to include any suitable stationary structure housing a shaft or rod to which a seal is secured.
As shown in
A sealing element, such as O-ring 188, is concentrically disposed about the rotary seal ring 20 to seal between the rotary seal ring 20 and the holder assembly 110. As shown, the O-ring 188 is preferably disposed about a radially outer surface 184 of an axially inner portion of the rotary seal ring 20 and seals against the radially inner surface 124 of the holder assembly 110. The radially inner surface 124 of the holder assembly 110 may include a detent groove 189 for receiving and seating the O-ring 188 disposed about the rotary seal ring 20 to facilitate assembly and operation of the mechanical seal and to maintain the rotary seal ring 20 in an optimal position.
Other sealing members can be provided to seal the interfaces between different components of the mechanical seal 10. For example, a flat annular elastomeric gasket 60 can be employed to seal the interface between the gland assembly 40 and the stationary equipment. Further, a holder gasket 160 can be mounted in a corresponding groove 158 to seal the holder segments 112 together if the holder assembly 110 is split. A holder/shaft elastomeric member, illustrated as O-ring 142, sits in a holder groove 140 formed along the inner surface 138 and seals between the rotary seal ring holder assembly 110 and the shaft. A stationary seal ring/gland elastomeric member, illustrated as O-ring 202, seals at an interface between the stationary seal ring 30 and the gland assembly 40 and provides radially inward pressure on the stationary seal ring 30. A gland gasket 76 can seat within a gland gasket groove 70 (
In addition, the illustrated split mechanical seal 10 can include an anti-rotation mechanism (not shown) such as a pin or a flat surfaced element that extends axially between the rotary seal ring 20 and the holder assembly 110 to prevent relative rotary movement between the rotary seal ring and the holder assembly 110. Those of ordinary skill will also recognize that suitable fasteners, such as bolts, can be employed to secure together the gland halves and the holder halves. Certain components of the mechanical seal 10 of the present invention are similar to the mechanical seal assemblies described in U.S. Pat. Nos. 5,571,268, 7,708,283 and 10,352,457, the contents of which are herein incorporated by reference.
The illustrated holder assembly 110 for mounting the rotary seal ring 20 is disposed in a chamber 24 formed by the gland assembly 40, and spaced radially inward therefrom. It should be understood, however, that the holder assembly 110 need not be disposed within the gland assembly 40. Rather, the holder assembly 110 can be axially spaced from the gland assembly 40. The holder assembly 110 also includes an inwardly stepped surface that forms a second, axially-extending face 133. The radially inner surface 124 and the axially extending face 133 have a radially inward-extending first wall 132 formed therebetween. As shown, the inner axially extending face 133 and the radially innermost axially extending face or holder inner face 138 define an axially innermost second wall 134 therebetween that serves as the bottom of a cavity or seal ring receiving space 111 (
According to one embodiment, the sealing element or O-ring 188 for sealing between the rotary seal ring 20 and the rotary seal ring holder 110 seats in a groove 189, such as a detent groove, formed on the radially inner surface 124 of the holder assembly 110. The detent groove 189 is sized, located and configured to receive a radially outermost portion of the O-ring 188 so as to position and seat the O-ring 188 relative to the holder assembly 110 during installation without compromising performance. The detent groove 189 preferably seats the O-ring 188 above the stepped wall 132. Alternatively, the detent groove 189 seats the O-ring in another location between the holder assembly 110 and the rotary seal ring 20. A significant advantage of the detent groove 189 and the placement of the groove on the radially inner surface 124 of the holder is that it reduces the amount of compression needed to seat the O-ring 188 in the groove.
The illustrated rotary sealing ring 20 includes a substantially smooth arcuate inner surface 172 and an outer surface comprising several surfaces including a first outer slanted surface 182 that forms a skirt portion, a relatively flat outer surface 184, and an axially inwardly tapered or sloped outer surface 186. The rotary seal ring 20 also includes a smooth arcuate sealing surface 21 disposed at a top of the seal ring 20. A rotary seal ring detent groove 92 is formed on the flat outer surface 184 adjacent the first slanted surface 182, as best shown in
As shown in
As shown in
The inner diameter of the stationary seal ring 30 as defined by the inner surface 32 is greater than the shaft diameter, and can if desired be greater than the diameter of the inner surface 172 of the rotary seal ring 20, thereby allowing relative motion therebetween. Therefore, the stationary seal ring 30 remains stationary while the shaft rotates. An elastomeric sealing member, e.g., O-ring 202, provides a radially inward biasing force sufficient to place the seal ring segment sealing faces 35 in sealing contact with the other stationary seal ring segment. Additionally, the O-ring 202 forms a fluid-tight and pressure-tight seal between the inner surface 46 of the gland assembly 40 and the stationary seal ring 30. The O-ring 202 seats in a first mounting region 204 defined by the gland first face 46 and the annular wall 48 and the outer surface 190 of the stationary seal ring 30 when disposed in the loaded position. In a preferred embodiment, the abutment 192 of the stationary seal ring 30 forms an angle relative to the stationary seal ring outer surface 190 preferably in the range of between about 30° and about 60°, and most preferably about 45°. The stationary seal ring 30 is preferably composed of a carbon or ceramic material, such as alumina or silicon carbide and the like.
The biasing assembly of the split mechanical seal 10 of the present invention, illustrated as a biasing clip assembly 210, also functions as an axial biasing means by providing resilient support for the stationary and rotary seal rings 20, 30 by axially biasing the seal rings such that the stationary and rotary sealing surfaces 21 and 31 are disposed in sealing contact with each other. As illustrated in
The mechanical seal 10 of the present invention preferably employs a series of biasing clip assemblies 210 that are mounted on the axially outermost end of the gland assembly 40. Since the biasing clip assemblies 210 are identical, we need only describe herein one of the clip assemblies. The biasing clip assembly 210 preferably employs a pair of generally C-shaped spring clips defined as an inner spring clip 216 and an outer spring clip 218. The inner spring clip 216 has a first lower end that has a ridge portion 220 that seats within a recessed portion 242 of the spring holder plate 230. The engagement of the ridge portion 220 of the inner spring 216 with the recessed portion 242 helps secure the inner spring clip 216 thereto. The inner spring clip 216 further includes at an opposite end a bent portion 222 that seats on or can be disposed in contact with the recessed portion 196 formed in the top surface 194 of the stationary seal ring 30 to provide an axial biasing force thereto. The bent portion 222 thus functions as an axial biasing member for applying an axial biasing force to the seal rings 20, 30. The axial biasing force as is known to those of ordinary skill in the art is an inboard directed force that helps place the seal faces 21, 31 of the seal rings 20, 30, respectively, in sealing contact with each other.
The illustrated mechanical seal 10 also includes an axially movable spring holder plate 230, as shown for example in
The biasing clip assembly 210 of the mechanical seal 10 of the present invention includes an outer spring clip 218 that is adapted to be mounted over the inner spring clip 216. The outer spring clip 218 has a main body that includes a generally rounded first end portion 224 that is configured to be mounted on and engage the outer surface of the inner spring clip 216, as best illustrated in
In assembly and during operation, the mechanical seal 10 can be composed of four selected halves or segments that have selected seal components that are preassembled together to form subassembly units. For example, as shown in
Similarly, as shown for example in
When assembling together the holder and gland subassembly units, the sealing elements, such as for example the O-rings 188, 202, can become pinched when the O-rings are moved from the unloaded position to the loaded position. For example, as the O-rings are compressed radially, they expand circumferentially with the ends of the O-ring segments protruding, potentially buckling when joined, thereby causing pinching by metal or seal face parts at the location of the split. In order to prevent this from occurring, the present invention provides for a selected assemblage of components that forms a loading assembly that does not prematurely load the O-rings 188, 202 prior to assembly of the subassembly units about the shaft 12, thus preventing the O-rings 188, 202 from extruding past the end faces of the holder and gland segments.
With regard to the holder subassembly units 270, each of the O-ring segments 188 are concentrically disposed about the rotary seal ring segments 20 and are preferably disposed in contact with the rotary seal ring outer surfaces 182, 184 and the rotary seal ring detent groove 92 to form the rotary seal ring pre-assembly. The O-ring 188 and the rotary seal ring 20 are mounted in the holder assembly 110 such that the O-ring 188 seats within the detent grooves 189, 92 formed in the surfaces 124, 184. This prevents, reduces or minimizes premature and unwanted loading of the O-ring 188 when the holder subassembly units 270 are assembled together. As such, the end regions of the O-ring segments do not extrude past the end faces of the holder and gland segments. The holder pre-assembly units 270, 270 are then disposed about the shaft 12. A coupling mechanism, such as a drive flat, can be employed to rotationally couple the rotary seal ring 20 to the holder assembly 110 for relative rotation therewith. The coupling mechanism can be disposed on either the holder assembly or the rotary seal ring, and in a preferred embodiment, is disposed on both the rotary and stationary seal rings. The detent groove 189 of the holder assembly 110 and the detent groove 92 of the rotary seal ring 20 receive and retain the O-ring 188 in an optimal position. The O-ring 188 provides an inward radial force sufficient to place the axial seal faces 25 of the rotary seal ring segments in sealing contact with each other. The holder segments are then secured together by tightening the screws 170 that are positively maintained in the fastener-receiving apertures 164. The rotary seal ring segments are spaced from the inner surface 124 of the holder assembly and are non-rigidly supported therein by the O-ring 188, thereby permitting small radial and axial floating movements of the rotary seal ring 20. When disposed within the detent grooves, the O-ring 188 is disposed in the unloaded position.
With regard to the gland pre-assembly unit 260, the O-ring 202 is disposed about the stationary seal ring 30 and then disposed adjacent the lead-in surface 52 formed along the inner surface of the gland assembly 40. The springs 86 are mounted within the corresponding spring holes 64 formed in the top surface 62 of the gland assembly 40. The spring holder plate 230 is secured to the gland assembly top surface 62 by partially tightening the bolts 250 in the fastener holes 66. The spring holder plate 230, the springs 86 and the bolts 250 can form the loading assembly. The multiple biasing inner clips 216 are mounted along the perimeter or circumferential edge of the top surface 61 of the gland assembly. The ridge portion 220 of the first end of the inner spring clip 216 is mounted in the recessed portion 242 formed in the bottom surface 238 of the spring holder plate 230. The outer spring clip 218 when mounted on the inner spring clip 216 has the bent tab portion 228 that has an edge or tip that seats in the groove 33 formed in the inner surface 32 of the stationary seal ring 30. The O-ring 202 is captured between the lead-in surface 52 (
As shown in
The illustrated loading assembly can thus be employed to axially move the O-rings 202, 188 into the engaged and loaded position where they are radially compressed. The O-rings are compressed after the gland and holder subassembly units have been assembled and secured around the shaft 12 and to the stationary equipment. The loading assembly of the present invention avoids having the O-rings extrude past the end faces prior to assembly where they can be pinched when the subassembly units are secured together. Since the gland and holder surfaces defining the regions mounting the O-rings 202, 188 are in contact with each other prior to the O-ring being radially compressed in the sealing location, there is no protruding end of the O-ring segments with the potential resulting misalignment of the sealing elements.
The spring holder plate 230 further includes segments 231, 233 that are secured together using male and female types mechanical connections. The spring holder plate 230, prior to being tightened by the operator, serves to hold the rotary and stationary O-rings 188, 202 in a free state or unloaded position during the securing of the gland and holder subassembly units 260, 270 around the shaft 12. The preassembled subassembly units 260, 270 allow for sequenced installation of the units. Specifically, the holder subassembly units 270 (e.g., rotary subassembly units) are secured to the shaft 12 and then the gland subassembly units 260 (e.g., stationary subassembly units) are secured around the rotary components and to the stationary equipment. The axial movement of the spring holder plate 230 via the bolts 250 pushes the seal faces 21, 31 and the rotary and stationary O-rings 188, 202 into their operating locations. As such, a single element can be used to displace the O-rings 188, 202 from a radially uncompressed state (e.g., unloaded position) to a compressed energized state (e.g., loaded position).
It will thus be seen that the invention efficiently attains the objects set forth above, among those made apparent from the preceding description. Since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are to cover all generic and specific features of the invention described herein, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.
Having described the invention, what is claimed as new and desired to be secured by Letters Patent is:
The present application claims priority to U.S. provisional patent application Ser. No. 63/035,504, filed on Jun. 5, 2020, and entitled EXTERNALLY ENERGIZED SECONDARY SEALS IN SPLIT MECHANICAL SEALS, the contents of which are herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63035504 | Jun 2020 | US |
