Patent Application
20130039754
1. Field of the Invention
The present invention relates to a pump or pumping assembly, arrangement or combination; and more particularly relates to a new technique for providing axial thrust in such a pump or pumping assembly, arrangement or combination, e.g., including a vertical double-suction pump.
2. Brief Description of Related Art
Single-suction type impellers produce hydraulic thrust loads in the direction along their axis of rotation. In a vertically suspended pump, these axial thrust loads are transmitted from the impeller(s) at the bottom of the pump rotor assembly, through the shaft of the pump, and absorbed by a thrust bearing in the motor at the top of the pump. Axial thrust loads are beneficial in vertical pumps for two reasons:
Typical double-suction type impellers produce no axial thrust loads from hydraulic forces; because their symmetrical geometry about the centerline of the impeller has the same pressure acting on both shrouds. Therefore, when typical double-suction impellers are used in vertically suspended pumps, the benefits of axial thrust loads pump shafts are not realized, and these types of pumps suffer from poor reliability.
In view of the aforementioned, there is a long felt need in the industrial pump industry for an improved design or technique that solves the problems related to realizing axial thrust loads in an industrial pump or pumping assembly, arrangement or combination, including a vertical double-suction pump.
According to some embodiments of the present invention, apparatus, including for example a vertical double-suction pump, is provided featuring a pump casing and a double suction impeller arranged therein on a shaft. The pump casing has a pump casing wall. The double suction impeller has upper and lower shrouds with metal rims configured to form upper and lower isolating annuli or rings between the double suction impeller and the pump casing wall of the pump casing in order to impede a recirculation flow from an impeller discharge to be able to act upon the upper and lower shrouds and create a controlled axial thrust load from differentiated hydraulic pressure on the upper and lower shrouds.
In effect, the present invention provides a special double-suction type impeller design, which creates the controlled axial thrust load from differentiated hydraulic forces acting on the impeller shrouds. The metal rims or rings on the upper and lower shrouds of the double-suction impeller design create or form the isolating annuli or rings between the double suction impeller and the pump casing wall. The isolation occurs as a result of the metal rim impeding the recirculation flow from the impeller discharge to be able to act upon the upper and lower impeller shrouds. The upper and lower isolating annuli or rings may be geometrically varied between the upper and lower shrouds of the impeller, which creates a pressure differential in the direction parallel to the axis of impeller rotation. Thus axial thrust load is created on a double-suction impeller design which normally has no substantial hydraulic thrust load in the direction of the axis of rotation.
When this innovative double-suction type impeller design is used in vertically suspended pumps, the benefits are at least as follows:
The drawing includes the following Figures, not necessarily drawn to scale:
In the following description of the exemplary embodiment, reference is made to the accompanying Figures in the drawing, which form a part hereof, and in which is shown by way of illustration of an embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized, as structural and operational changes may be made without departing from the scope of the present invention.
In
In operation, the pair of isolating annuli 22 and 24 between the double suction impeller 14 and pump casing wall 16 reduces internal leakage in the pump 10, which improves volumetric efficiency and overall pump efficiency, and also dampens secondary flows from pump casing recirculation and isolates such flows from buffeting the upper and lower shrouds 18 and 20 of the double suction impeller 14. This mitigates undesirable axial vibration on the overall pump rotor system of the apparatus 10.
According to some embodiments, the upper and lower isolating annuli 22 and 24 may also be geometrically varied between the upper and lower shrouds 18 and 20 of the double suction impeller 14 to create a pressure differential in a direction parallel to an axis A of rotation of the double suction impeller 14.
The upper and lower isolating annuli 22 and 24 may be configured to create the controlled axial thrust load LA on the double suction impeller 14 which typically has substantially no hydraulic thrust load in the direction of the axis A of rotation.
The upper and lower isolating annuli 22 and 24 may be configured to form an isolated section generally indicated by arrow 30 along the upper or lower shrouds 18 and 20 extending at least partly towards the shaft 15. (In
The metal rims 22 and 24 may be configured to be located at a minimum trim value in relation to the outside diameter of the double suction impeller 14, as shown, e.g., in
Moreover, the apparatus 10, e.g., as shown in
It should be understood that, unless stated otherwise herein, any of the features, characteristics, alternatives or modifications described regarding a particular embodiment herein may also be applied, used, or incorporated with any other embodiment described herein. Also, the drawings herein are not drawn to scale.
Although the invention has been described and illustrated with respect to exemplary embodiments thereof, the foregoing and various other additions and omissions may be made therein and thereto without departing from the spirit and scope of the present invention.
