GB2036869A

GB2036869A - Submersible Motor Pump

Info

Publication number: GB2036869A
Application number: GB7942765A
Authority: GB
Original assignee: Klein Schanzlin and Becker AG
Current assignee: Klein Schanzlin and Becker AG
Priority date: 1978-12-13
Filing date: 1979-12-12
Publication date: 1980-07-02
Also published as: DE2853744A1; ZA796769B; PL220293A1

Abstract

The shaft of the electric motor 1 extends axially from the rotor at either end to provide shaft end portions 2a and 2b which carry respective shaft extensions fixed thereto, each shaft extension carrying the respective pair of centrifugal impellers 4 which form parts of two respective stages of the pump, which has four stages in all, the first two stages being located at the end of the pump adjacent shaft end portion 2a and the last two stages being located at the end of the pump adjacent shaft end portion 2b. Each stage, and thus each impeller 4, is of the single suction stage, and the two impellers 4 carried by each shaft end portion 2a, 2b, have their inlet eyes facing towards the rotor of the motor, and thus facing in opposite directions at opposite ends of the rotor shaft, so that in operation, the thrust applied to the rotor shaft by the impellers at one end of the shaft is balanced by the thrust applied by the impellers at the other end of the shaft, thereby eliminating the need for substantial axial or thrust bearings. <IMAGE>

Description

SPECIFICATION Submersible Motor Pump This invention relates to a submersible motor pump, comprising a plurality of single-suction stages and having a motor which includes a rotor having respective shaft end portions extending axially from oppositeends thereof and drivingly connected with respective impellers or groups of impellers of the pump.

In a known pump of this kind disclosed in United States Patent Specification 2,450,137 one or more impellers are disposed below the motor, (arranged with its rotary axis vertical) and the delivery from the impellers is guided along the motor into other stages of the pump which are disposed above the motor and which discharge to a pipeline. This kind of construction is used to pump volatile liquids; the pump stage below the motor acts merely as an intake stage. It is difficult to compensate for axial thrust in the known construction. Consequently, in the prior art the various stages above the motor are disposed oppositely with respect to one another, while an elaborate axial bearing is provided for the first impeller, the same being disposed below the motor.Unfortunately, this form of compensation for axial thrust becomes unsatisfactory when the pump has to operate with corrosive or abrasive media, for such compensation would become increasingly ineffective with increasing wear, with the result that the axial bearing in the motor would be overloaded.

It is an object of the invention to devise a submersible motor pump having an axial thrust compensating means substantially unaffected by wear.

According to the invention, therefore, there is provided a submersible motor pump comprising a plurality of single-suction stages and having a motor which includes a rotor having respective shaft end portions extending axially from opposite ends thereof and drivingly connected with respective impellers or groups of impellers of the pump, the or each impeller associated with each shaft end portion having its eye facing in the axial direction which is opposite to that in which the eye of the or each impeller associated with the other shaft end portion faces.

This disposition of the impellers oppositely to one another on the two shaft end portions provides substantially complete compensation for axial thrust during normal operation. However, a small axial bearing may be necessary for starting, depending upon operating conditions. Another advantage of the invention is that the shaft diameters in the parts of the pump need be designed only for half the total power so that material is saved and the hydraulic shaping at the impeller entry can be improved, as compared with known constructions.

Arranging the stages of the pump above and below the motor (the pump being considered in its normal operating position with the rotary axis of the motor vertical) enables the bottom part of the pump-which part preferably also comprises the pump intake orifice-to be devised as a lowpressure part and the upper part of the pump (i.e.

the part above the motor) to be devised as a highpressure part, again with the result of reducing the material required, in this case for the expensive castings of the various stages.

A particular advantage provided by the invention is that the hydraulic side of the system-i.e. the impellers and diffusers-can be optimized for particular delivery requirements.

The hydraulic efficiency of a centrifugal pump depends upon the specific speed nq: Q 1/2 nq=n.

H 314 Thus, where n is the rotational speed, Q is the delivery rate (volume/unit time) and H is the head.

The construction according to the invention is particularly well suited to high-delivery pumps. If delivery is relatively small, the specific speeds nq are low in double-suction pumps-i.e. efficiencies are low-and it becomes difficult to produce the impellers and diffusers since the flow channels become very narrow.

The specific speed of the single suction arrangement in embodiments of the invention is greater by pathan in the double suction construction.

Also, it is simpler to assemble and easier to transport a submersible motor pump embodying the invention, since, in its preferred form, the pump can be transported "knocked-down" and fully assembled in sits.

An embodiment of the invention is shown in the drawing and will be described in greater detail hereinafter.

The drawing shows a submersible motor pump, i.e. a centrifugal pump driven by an electric motor 1 of the submersible type.

The motor 1 comprises a stator mounted in a motor jacket 9 and a rotor mounted for rotation within the stator, the rotor being carried by a shaft rotatably mounted in bearings and having respective end portions 2a, 2b, extending axially in opposite directions from respective opposite ends of the rotor. The motor is intended to be operated with the rotary axis of the rotor and said shaft extending vertically, with the shaft end portions 2a lowermost, and terms such as "upper" and "lower", "top" and "bottom", are used herein to refer to the pump in its normal operating position.

In the embodiment shown, a respective further shaft portion, formed separately from the shaft on which the rotor 1 is mounted, is secured to the free end of each end portion 2a, 2b, as an axial extension thereof, by means of a releasable coupling arrangement including a respective sleeve receiving the adjacent ends of the respective shaft end portion 2a or 2b and the respective further shaft portion. These further shaft portions are journalled for axial rotation in respective end casing parts detachably secured to the motor jacket 1, and each said further shaft portion has secured thereto a respective pair of impellers 4 cooperating with respective stationary parts 5 carried by or provided by, the respective end casing parts to define therewith respective stages of the pump.

The releasable connection of these further shaft portions with the main shaft to which the motor rotor is directly secured, and the detachable mounting of the end casing parts on the motor jacket allows the pump parts above and below the motor to be readily disconnected from the motor for ease of transportation and the like, but for other purposes these further shaft portions can be regarded as forming parts of the respective shaft end portions.

The end casing part below the motor comprises an intake casing 3 which defines the intake orifices of the pumps, which lead to the first pump stage, from which, in operation, fluid being pumped passes to the second pump stage, the first and second pump stages being defined by the two impellers 4 carried by the lower shaft end portion 2a in conjunction with stationary parts forming appropriate diffusers and flow channels.

The impellers 4, whether above or below the motor, and consequently the respective pump stages, are of the single suction type, i.e. each impeller has an inlet eye at only one axial end thereof, (as opposed to the double suction type of centrifugal pump impeller which has an inlet eye at both axial ends thereof and in operation of which fluid is drawn axially into each eye, moving in opposite axial directions into the two eyes to pass outwardly on opposite sides of a central web of the impeller extending generally normal to the axis of the impeller).

The eyes of the impellers 4 below the motor 1 face upwardly towards the motor 1, while the eyes of the impellers 4 above the motor face downwardly, towards the motor 1.

The inlet orifices of the pump are disposed closer to the motor than the diffusers 4 secured to the lower shaft end portion, and in operation, fluid being pumped is drawn into the intake orifices to pass, as indicated by the arrows, in the direction away from the motor into the eye of the firststage impeller, through the associated diffuser and flow passages into the eye of the secondstage impeller 4, disposed lowermost in the drawing, and passing from the second stage is deflected within a casing part 6 forming a portion of the lower casing end part, to return through ducts 7 in the lower casing end part, towards the motor and pass from ducts 7 through registering ducts in the motor jacket 9, along and past the motor to the pump part at the upper end thereof, the medium pumped acting as a coolant as it moves past the motor 1.

The pumped fluid, after passing the motor, passes upwardly via ducts in the upper end casing part into the eye of the third stage impeller and thence, via the associated diffuser and flow passages etc. upwardly into the eye of the fourth stage impeller to pass from the fourth stage upwardly through a central outlet orifice at the upper end of the pump.

Because the impellers 4 above and below the motor all have their eyes directed towards the motor 1, the axial thrusts produced in the two parts of the pump acts towards the motor and so the axial thrusts at opposite ends of the rotor cancel one another out.

Consequently, an axial bearing is necessary only for the short starting and stopping period of the pump.

Claims

1. A submersible motor pump comprising a plurality of single-suction stages and having a motor which includes a rotor having respective shaft end portions extending axially from opposite ends thereof and drivingly connected with respective impellers or groups of impellers of the pump, the or each impeller associated with each shaft end portion having its eye facing in the axial direction which is opposite to that in which the eye of the or each impeller associated with the other shaft end portion faces.

2. A submersible motor pump according to claim 1 in which the eyes of the impellers associated with each shaft end portion face towards the rotor of the motor.

3. A submersible motor pump according to claim 1 or claim 2 wherein said shaft end portions are associated with equal numbers of impellers, each impeller serving a respective single-suction stage of the pump.

4. A submersible motor pump substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.

5. Any novel feature or combination of features disclosed herein.