Patent Application
20170292527
The present disclosure is directed to high speed centrifugal pumps and more particularly to a lined space behind the pump impeller and seal housing.
Centrifugal pumps are common for transporting fluids. Centrifugal pumps help convert rotational kinetic energy into hydrodynamic energy, helping move fluid from one place to another. Commonly, a centrifugal pump uses an impeller, which spins rotationally and is connected to a fluid source. The impeller often resembles a disc with a series of blades or extensions, or a disc with channels on one side. The impeller spins, causing a pressure differential. This pressure differential pulls fluid into the housing. The impeller will direct the fluid into a second channel or pipe for transport to another location.
Current designs of high speed centrifugal pumps typically utilize metallic components for stationary surfaces. Behind the impeller there can be a seal housing. The seal housing contains the seals that seal the shaft and prevent pumped fluid from entering the gears, and other parts of the machinery. One problem with current solutions is that sticky or gritty pumped fluids can get stuck at various parts of the machinery, in particular in the seal chamber causing pump failure. At the same time, if the pump is transporting water, it can be very important to prevent the pumped fluid from penetrating into the seal chamber and causing fouling. One solution for preventing build up has been to use polymer-based linings, or rubber. But these solutions have been limited to low speed pumps, e.g. below 3600 rpm.
One embodiment of the present disclosure comprises a centrifugal fluid pump comprising: an impeller operable, when spun rotationally, to cause a pressure differential and pull fluid from an inlet and direct the fluid toward an outlet; a shaft operable to move the impeller rotationally; a seal casing operable to fit around the shaft; a cover operable to fit around the shaft and on a side of the seal casing proximate the impeller; a seal operable to fit around the shaft and on a side of the seal casing distal the impeller; and a lining attached to a surface of the seal casing that faces the shaft, wherein the lining comprises a hard polymer and is to isolate and protect the seal chamber.
Another embodiment comprises a pump casing for a centrifugal fluid pump comprising: an annular opening operable to receive a shaft therein and to allow the pump casing to fit along the shaft and proximate an impeller; and a polymer lining operable to attach to an inner surface of the annular opening facing the shaft, wherein the sleeve comprises a hard polymer and is capable of isolating the annular opening; wherein the annular opening is configured to create a seal chamber comprising the space between the inner surface and the shaft.
Another embodiment comprises a method of constructing a centrifugal pump comprising: providing an impeller operable, when spun rotationally, to cause a pressure differential and pull fluid from an inlet and toward an outlet; providing a shaft operable to move the impeller rotationally; providing a seal casing operable to fit around the shaft; providing a cover operable to fit around the shaft and on a side of the seal casing proximate the impeller; providing a seal operable to fit around the shaft and on a side of the seal casing distal the impeller; and attaching a lining to a surface of the seal casing that faces the shaft, wherein the lining comprises a hard polymer.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
Referring now to
Embodiments of pumps incorporating the concepts described herein use hard polymers instead of metallic parts on certain components in high speed pumps. For example, when the components of
The present teachings allow for operation in pumps at greater than 5,000 rpm. Using the present teachings to apply fluoropolymer, or another appropriate solid polymer, to interior portions of a pump, will generally be limited to portions near the center, e.g. near the shaft. The further out from the shaft that fluoropolymer is applied, the greater stresses will act on the fluoropolymer. Fluoropolymer can deform at high pressures and speeds. But near the shaft the fluoropolymer will remain undeformed and provide appropriate non-stick surface. Fluoropolymer will generally not be able to be applied to all the wetted components. Though at slower speeds, fluoropolymer cover 225 can be increased in diameter from the shaft.
The embodiments described use fluoropolymer (polytetrafluoroethylene) for the lining sleeve. While the preferred embodiment uses fluoropolymer, other embodiments may use other thermoplastic polymers with appropriate properties. Some embodiments may use fluoropolymer that is cross-linked or otherwise combined with other materials or substances. Fluoropolymer can refer to polytetrafluoroethylene (PTFE) or other polymers such as perfluoroalkoxy (PFA) or fluorinated ethylene propylene (FEP).
Seal housings or other components of fluid pumps are often manufactured with materials such as 316 stainless steel. Fluoropolymer can be applied to steel according to methods well known in the art. Materials besides stainless steel are possible for use in pump and pump components. Materials besides fluoropolymer may be useable for lining the interior of the seal casing according to the present teachings.
The embodiments of the teachings of the present disclosure have been illustrated with certain geometries. However, the current teachings can be implemented with various shapes of pumps, various impeller shapes, and across a variety of pump materials, sizes and geometries. Embodiments can include different types of pumps, including gas powered, electric powered, magnetic drive, or other types. In addition, the exact length and dimension of the lining sleeve (sleeve portion and plate portion) may differ according to the embodiment. In some embodiments, the plate portion will extend further out from the shaft, depending on the composition of the pumped fluid, speed or other characteristics of the given pump. The sleeve portion of the lining sleeve preferably covers an entire inner surface of the seal casing, however other geometries are possible. Some embodiments will comprise only a sleeve portion, or only a plate portion, as needed.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
