FIELD OF THE INVENTION

The invention relates to globe valves, and more particularly, to globe, angle, and sweep angle control valves that are subject to severe erosion due to particulate impacts. These valve types are referred to generically herein as “plug and seat” valves, indicating that a flow is being controlled between a plug and seat.

BACKGROUND OF THE INVENTION

Plug-and-seat valves are widely used for a variety of applications. With reference toFIG. 1A, a plug-and-seat valve assembly118controls fluid flow from an inlet114to an outlet116by actuating a plug assembly110such that a plug head100of the plug assembly110is moved closer to or further from a valve seat112.

While plug-and-seat valves are readily adapted to many applications, special problems arise when implementing plug-and-seat valves in extreme operating environments, such as when controlling process fluids that are at elevated temperatures and/or pressures, and/or are corrosive. In addition, plug-and-seat valves can be subject to severe and rapid erosion when controlling the flow of a slurry that contains both solids and fluids. This erosion is intensified when the plug is near the seat, such that the slurry is forced to flow rapidly between, and in close contact with, the seat and plug. Under such conditions, in the region of the plug and seat, the slurry is generally flowing away from, or parallel to, the surfaces of the seat, while flowing generally toward, and applying pressure to, the plug. As such, it is the plug that is the primary victim of abrasive erosion when controlling the flow of a slurry that contains a high concentration of abrasive particulates.

For these and other reasons, plug-and-seat valves that are designed for implementation under extreme conditions generally implement a plug assembly that include a hardened plug head attached to a metal plug stem. One approach to attaching the plug head to the plug stem is by soldering, welding or brazing. This approach is suitable, for example, when attaching a tungsten carbide plug head to a plug stem. However, this approach is limited by temperature, size, and the choice of materials.

Furthermore, ceramic plug heads, such as plug heads comprised of sintered silicon carbide (SSiC), are often preferable to metals such as tungsten carbide for extreme operating environments involving highly erosive and/or corrosive fluids and/or slurries, due to the higher resistance of ceramics to corrosion and erosion. Because ceramics are generally not compatible with soldering, welding, or brazing, this approach generally requires attachment of the ceramic plug head to the plug stem by a retainer assembly that captures the shaped body of the ceramic plug head and holds it against the plug stem. An example of such a plug assembly110is shown inFIGS. 1A and 1B, in which a ceramic plug head100is attached to a plug stem102by a retainer assembly that comprises a plug head retainer104attached to a plug head blank106, which in turn is attached to the plug stem102.

The erosion of plug head by slurries can be further reduced by carefully configuring the outer profile shape of the plug head such that the contour of the plug head varies gradually and smoothly as the slurry flows past the plug head, thereby minimizing obstruction of the slurry and encouraging laminar flow of the slurry near the plug head. This approach can be successful in valves where the plug head is directly attached to the plug stem by soldering, welding, or brazing. However, this approach can be difficult to implement when the plug head100, such as a ceramic plug head, is attached to the plug stem102by a retainer assembly104,106, as illustrated inFIGS. 1A and 1B. This is because the retainer assembly104,106must encapsulate the plug head100, and therefore some part104of the retainer assembly104,106must extend beyond the plug head100. In the example ofFIGS. 1A and 1B, it can be seen that a region108of the plug head retainer104extends beyond the profile of the plug head100, where it will be impacted and unduly eroded by particulates in a slurry.

What is needed, therefore, is a plug head assembly that includes a plug head, such as a ceramic plug head, that is attached to a plug stem by a retainer assembly, and in which the retainer assembly is not subject to undue erosion by particulates included in a process fluid slurry.

SUMMARY OF THE INVENTION

The present invention is a plug head assembly that includes a plug head, such as a ceramic plug head, that is attached to a plug stem by a retainer assembly, and in which the retainer assembly is not subject to undue erosion by particulates included in a process fluid slurry.

The plug head of the present invention is axially symmetric about a plug head axis, and includes a proximal first portion and a distal second portion, wherein the second portion has a diameter that smoothly increases axially from a distal end thereof to a proximal end thereof according to a plug diameter profile that is configured to minimize obstruction of the slurry and encourage laminar flow of the slurry near the plug head.

The diameter of the first portion of the plug head also varies, but is everywhere less than the plug diameter profile. Furthermore, the diameter of the first portion reaches a maximum at a location that is axially proximal to the juncture between the second portion and the first portion.

The proximal first portion of the plug head is surrounded by a plug head retainer of the retainer assembly. The plug head retainer has an interior diameter that conforms closely to the outer diameter of the first portion of the plug head, and an outer diameter that extends the plug diameter profile of the plug head, so that the process fluid transitions smoothly from the second portion of the plug head to the plug head retainer with minimal erosion of the plug head retainer. Because the diameter of the first portion reaches a maximum at a location that is axially proximal to the juncture between the second portion and the first portion, the plug head is constrained from axial movement in a distal direction relative to the plug head retainer.

In embodiments, the retainer assembly further includes a plug head blank that abuts a proximal face of the plug head and attaches to the plug head retainer, thereby capturing the plug head between the plug head retainer and the plug head blank. In various embodiments, fasteners such as pins or bolts are used to attach the plug head retainer to the plug head blank and/or to attach the retainer assembly to the plug stem.

In embodiments, the plug head retainer is configured to apply a radial compressive stress to the plug head, and in some embodiments the retainer assembly is configured to apply an axial compressive stress to the plug head.

A first general aspect of the present invention is a plug head assembly configured for implementation in a plug-and-seat valve. The plug head assembly includes a plug head that is axially symmetric about a plug head assembly axis, the plug head having a proximal first portion and a distal second portion, wherein the second portion has a second portion diameter that increases smoothly in a proximal direction from a distal end thereof according to a plug diameter profile, the first portion having a first portion diameter that is everywhere less than the plug diameter profile, and which reaches a maximum at a location that is proximally spaced apart from the second portion.

The plug head assembly further includes a plug stem centered along the plug head assembly axis, and a plug head retainer assembly comprising one or more retainer elements, the plug stem being proximally attached to the plug head retainer assembly, at least one of the retainer elements surrounding and capturing the first portion of the plug head while the second portion of the plug head extends distally beyond the retainer assembly, the plug head being thereby fixed to the plug stem by the plug head retainer assembly, the plug head retainer assembly and plug stem being thereby attached to the plug head without welding or adhesion of any element of the plug head retainer assembly or plug stem to the plug head, and wherein an outer surface of the plug head retainer assembly conforms with and extends the plug diameter profile of the plug head proximally of the second portion of the plug head.

In embodiments, the plug head is made of a ceramic.

In any of the above embodiments, the plug head retainer assembly elements can comprise a plug head retainer and a plug head blank configured for attachment to the plug head retainer, said plug head being captured therebetween, and wherein an outer surface of the plug head retainer conforms with and extends the plug diameter profile of the plug head.

In any of the above embodiments, the plug head retainer assembly can be configured to apply radially compressive stress to the plug head.

In any of the above embodiments, the plug head retainer assembly can be configured to apply axially compressive stress to the plug head.

And in any of the above embodiments, the plug diameter profile of the plug head can be configured to provide equal percentage characteristics to the plug head assembly, or linear characteristics to the plug head assembly.

A second general aspect of the present invention is a plug-and-seat valve suitable for controlling a flow of a slurry containing a high concentration of abrasive particulates, the plug-and-seat valve comprising a plug assembly according to the first general aspect, a valve seat, and a housing, the plug assembly being configured for translation within the housing toward and away from the valve seat.

In embodiments of the second general aspect, the plug head is made of a ceramic.

In any of the above embodiments of the second general aspect, the plug head retainer assembly elements can comprise a plug head retainer and a plug head blank configured for attachment to the plug head retainer, said plug head being captured therebetween, and wherein an outer surface of the plug head retainer conforms with and extends the plug diameter profile of the plug head.

In any of the above embodiments of the second general aspect, the plug head retainer assembly can be configured to apply radially compressive stress to the plug head.

In any of the above embodiments of the second general aspect, the plug head retainer assembly can be configured to apply axially compressive stress to the plug head.

And in any of the above embodiments of the second general aspect, the plug diameter profile of the plug head can be configured to provide equal percentage characteristics to the plug head assembly, or linear characteristics to the plug head assembly.

The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter.

