GB2045351A

GB2045351A - Rotary Pitot Pumps

Info

Publication number: GB2045351A
Application number: GB8009619A
Authority: GB
Original assignee: Kobe Inc
Current assignee: Kobe Inc
Priority date: 1979-03-23
Filing date: 1980-03-21
Publication date: 1980-10-29
Also published as: JPS55151193A; DE3007188A1; GB2045351B

Abstract

The pump comprises a rotatable housing 10 having a fluid inlet 37 and containing a rotatable chamber 15 and accelerating passages 30. The housing is formed of high structural strength material and is lined with corrosion resistant material. The lining 30 of the annular end wall 20 carries a plurality of vanes 32 and there is an annular sheet 33 of corrosion resistant material to define the accelerating passages. <IMAGE>

Description

SPECIFICATION Rotary Pumps The invention relates to a modification of high speed rotary pumps so as to make them more suitable for handling corrosive fluids.

A commercially available rotary fluid pump used in many industries, but particularly in connection with the pumping and transportation of oil, is an apparatus wherein the only rotary element of the pump comprises a pair of housings secured together to form a rotating fluid chamber. Within such chamber, a stationary pickup tube of the pitot type is disposed with its opening located near the periphery of the rotating chamber and facing the rotary flow of the fluid in the rotary chamber. Such pickup tube communicates with an axial central pipe forming the pressured fluid discharge passage for the pump, while the fluid inlet to the rotating pumping chamber is provided by an annular axial passageway surrounding the discharge pipe so that only a single rotating fluid seal is required for the entire pump.

Generally, the rotating fluid chamber is defined by a unitary cup shaped member which can only be economically manufactured by casting techniques, while the open face of the cup shaped member is closed by a cooperating annular casting defining a central opening for surrounding the stationary fluid discharge conduit and providing an axial inlet conduit for the fluid, and, in addition, defining a plurality of radial accelerating passages for the inlet fluid which impart a substantial rotational velocity to the inlet fluid as it enters the rotating chamber.

These pumps have been subject to a serious limitation in rotational speed whenever corrosive fluids are to be pumped. Corrosive fluids can only be effectively handled by corrosion resistant material such as stainless steel, but stainless steel castings have significantly less tensile strength than many other steels which do not have the corrrosion resistance of stainless steel.

Accordingly rotary pumps formed of stainless steel suffered from limitations in either fluid capacity or maximum pressure developed due to the fact that either the diameter of the pump casting had to be limited, or the rotational speed of the rotating castings had to be reduced in order to avoid breaking of the pump by the centrifugal stresses generated in the castings.

In the invention an improved rotary chamber type pump is provided for the pumping of corrosive fluids wherein the rotational speed or the diameter of the pump can be significantly increased over that permitted by utilization of stainless steel castings without subjecting the fluid engaging elements of the pump to rapid corrosion by the corrosive fluid being pumped.

In brief, this invention constructs the rotary chamber type pump so as to provide two distinct groups of elements defining such rotary chamber respectively having two different functions. The one set of elements provides the stress or load carrying ability of the construction while the other set of elements constitutes all surfaces of the pump that are in contact with the fluid being pumped and provides the required corrosion resistance to such fluid. In other words, the pump is designed so that the structural portion of the rotating pumping chamber may be defined by castings formed from high tensile strength steel, while the fluid engaging components of the pump, including the inlet and accelerating passages may be defined by stainless steel elements so as to provide optimum corrosion resistance.

A rotary pump according to the invention comprises a rotatable housing having a fluid inlet in an annular end wall and about which the pump may rotate and the housing contains a rotatable chamber and accelerating passages for leading fluid from the inlet to the chamber and is formed of material of high structural strength and is lined entirely with corrosion resistant material and the lining on the annular end wall has on its inner face a plurality of vanes each of which has an end adjacent the inlet and leads radially away from the inlet, and there is an annular sheet of corrosion resistant material secured to the vanes thereby defining, with the vanes and the lining on the annular end wall of the housing, the radially extending accelerating passages.

Since the housing is made primarily of high structural strength material, normally cast high tensile strength steel, the pump housing can be subjected to substantially the same centrifugal forces as conventional pumps used for pumping non-corrosive liquids. However since the chamber is lined with corrosion resistant material and the accelerating passages are formed of corrosion resistant material corrosion within the pump is minimised ever when using corrosive liquids.

Naturaliy it is desirable that all parts that will be contacted by the liquid should be formed of corrosion resistant material, including the pick-up tube or tubes. The corrosion resistant material is generally stainless steel. It will of course be in a snug fit with the contours of the housing parts that it is lining.

The housing will normally have an outlet for the pump fluid and the inlet is generally an annular inlet around this outlet and the pump will include at least one pick-up tube formed of corrosion resistant material and leading to the outler and that has an orifice positioned near the radially outer portion of the chamber to face the rotational flow of the fluid within the chamber during rotation of the chamber relative to the tube.

The housing is generally formed of a cup shaped portion defining the rotational chamber and an annular portion. The annular sheet of corrosion material defining the accelerating passages may have its outer portion secured to the rim of the cup shaped portion and will then have apertures through it for passage of fluid from the radially outer ends of the accelerating passages into the chamber. The lining on the cup shaped portion may abut the lining on the annular portion and there may be a fluid seal between the abutting surfaces.

One preferred form of pump according to the invention comprises a cup shaped rotatable housing formed of high tensile strength material; a thin sheet of stainless steel shaped to conform to the radial wall and the peripheral wall of the inner surface of the cup shaped housing, thereby defining a major portion of a rotating fluid chamber; the other axial end wall of said chamber being defined by a high strength annular cover shaped to define a centrifugally resistant annular pocket; an annular lining of stainless steel snugly supported in said pocket, said stainless steel lining having a plurality of radial vanes on its inner face having their radially inner ends disposed adjacent to an annular fluid inlet passage; and an annular sheet of stainless steel integrally secured to said vanes to define radial fluid accelerating passages, whereby all fluid engaging portions of said rotary chamber are defined by corrosive resistant material while the centrifugally stressed portions of the rotary pump are fabricated from high tensile strength material.

Another rotary pump according to the invention has a rotating fluid pumping chamber, an axial, annular fluid inlet passage and radial accelerating passages connecting with said chamber, and at least one stationary fluid pickup tube having a hollow, radial portion defining an inlet opening disposed in the radially outer portions of said chamber and facing the rotational flow of fluid in the rotating chamber, and a hollow, axial portion disposed within said annular fluid inlet passage and defining a pressured fluid discharge passage, the improvement comprising a liner of corrosion resistant material shaped to conform to the one radial end wall and the peripheral wall of said fluid chamber; the other radial end wall being defined by a high strength annular element defining a centrifugally resistant annular pocket; an annular element of corrosion resistant material snugly supported in said pocket, said corrosion resistant element having a plurality of radial vanes on its inner face having their radially inner ends disposed adjacent to said annular fluid inlet passage; and an annular sheet of corrosion resistant material integrally secured to said vanes to define the radial fluid accelerating passages, whereby all fluid engaging portions ot said rotary chamber are defined by corrosion resistant material while the centrifugally stressed portions of said rotary chamber are defined of high tensile strength materials.

The invention is now described with reference to the accompanying drawings in which: Figure 1 is a schematic vertical sectional view of a rotary chamber pump according to this invention.

Figure 2 is a reduced scale sectional view of Figure 1 taken on the plane 2-2 of Figure 1.

Referring to Figure 1, the basic elements of a rotary chamber type pump 1 are therein shown.

The rotary portion of pump 1 comprises two structural elements, respectively a cup shaped casting 10 and an annular cover casting 20. The castings 10 and 20 are secured together by suitable bolts 11 provided around their abutting peripheries and a fluid seal is provided therebetween in a manner to be hereinafter described. The cup shaped casting 10 has a central axial recess 1 0a by which it is secured in conventional fashion to the end of a rotating shaft (not shown). Thus rotational movement is provided to the pumping chamber 1 5 defined between the structural members 10 and 20.

Each of the members 10 and 20 are formed by casting of high tensile strength steel so as to provide maximum resistance to the centrifugal forces inherently generated when such elements are rotated at high speeds. Additionally, cover casting 20 has an internal surface 20a terminating in an axial peripheral flange 20b to define an annular pocket resistant to centrifugal forces.

The entire inner surface 1 Ob of the cup shaped structural element 10 is covered by a thin sheet 25 of stainless steel which is pressed to exactly conform to the interior surface 1 Ob of casting 1 0.

Stainless steel sheet element 25 extends radially outwardly as indicated at 25a around the perimeter of radial flange 1 Oc formed on the structural element 10.

A lining element 30 is provided for the internal surface 20a of the cover casting 20. Liner 30 is formed from a stainless steel casting and it fits snugly within the annular pocket defined by flange 20b. Thus, it has a thickened annular hub portion 31 which receives a plurality of bolts 36 which respectively project through suitable holes provided around a collar 35, which not only effects the anchoring of the structural cover casting 20 to the corrosive resistant liner portion 30 but also provides a mounting for an annular fluid seal 37 which is required to prevent leakage of the inlet fluid entering the axial bore 30a of the corrosion resistant liner 30 and a conventional stationary casing (not shown) of the pump which provides appropriate support for the tubular discharge conduit 41 of the stationary pitot type, pickup tube 40.

Pickup tube 40 is of conventional configuration having a radially extending portion 40a terminating in a fluid inlet 40b which opens against the rotational flow of the fluid contained in the rotary chamber 1 5. Opening 40b is connected by a suitable diverging interior passageway (not shown) in tube 40 by which the rotational energy of the fluid is diffused to create a pressure head and is discharged through the bore of the axially extending discharge conduit 41.

The corrosion resistant liner 30 is additionally provided with a plurality of radially extending vanes 32 which radially accelerate the fluid entering the inlet passage 30a. To ensure the maximum rotational acceleration of the inlet fluid by the vanes 32, a cover plate 33 comprising an annular disc portion 33a and an axially enlarged hub portion 33b is proveded. Portions 33a and 33b are both formed from stainless steel and their abutting surfaces are brazed together to provide an integral construction. The inner peripheral surface 33c of hub portion 33b is disposed in close proximity to an enlarged flange 41 a provided on the tubular discharge conduit 41 so as to prevent any significant leakage of the inlet fluid into the rotary chamber 1 5 at that point.

Additionally, the disc portion 33a is brazed to the end faces of the vanes 32. Adjacent the outer ends of vanes 32, the disc portion 33a is provided with a plurality of peripherally spaced orifices 33d which discharge the rotationally accelerated fluid into the rotating pumping chamber 1 5.

Annular seal 34 is provided between the inwardly facing end 30c of the corrosion resistant lining element 30 and the outwardly facing surface of the flange 25a of the corrosion resistant cover sheet 25.

It is therefore apparent that the aforedescribed construction provides a rotary pump wherein all of the centrifugal forces generated by the rotation of the rotary pumping chamber is effectively absorbed by the structural members 10 and 20 which are cast from high tensile strength steels and hence provide tensile strength on the order of three to five times that available from stainless steel castings.On the other hand, all of the fluid engaging surfaces of the rotating components of the pump, such as the internal surface 25b of the cover sheet 25, both surfaces of the corrosion resistant cover plate 33, and the radial fluid accelerating passages defined by the vanes'32, the disc 33a and the inwardly facing surface 30b of the corrosion resistant liner 30 are all formed from stainless steel and provided optimum resistance to corrosive fluids passing through the pump. Obviously, the pitot type pickup tube 40 will also be formed from stainless steel, but this element, being stationary, is not subjected to any significant structural forces.

It is therefore apparent that the pump design of this invention splits the functions of stress resistance and corrosion resistance between two groups of components, each group being formed of a material that provides the optimum characteristics for the function that such group is to perform. ~~~~~~~~~~~~~~~

Claims

1. A rotary pump comprising a rotatable housing having a fluid inlet in an annular end wall and about which the pump may rotate and in which the housing contains a rotatable chamber and accelerating passages for leading fluid from the inlet to the chamber and is formed of material of high structural strength and is lined entirely with corrosion resistant material and in which the material lining the annular end wall has on its inner face a plurality of vanes each of which has an end adjacent the inlet and leads radially away from the inlet and in which there is an annular sheet of corrosion resistant material secured to the vanes thereby defining, with the vanes and the lining on the annular end wall of the housing, the radially extending accelerating passages.

2. A pump according to claim 1 in which the housing has an outlet for pumped fluid and the inlet is an annular inlet around this outlet and there is at least one pickup tube formed of corrosion resistant material leading to the outlet and that has an orifice positioned near the radially outer portion of the chamber to face the rotational flow of fluid within the chamber during rotation of the chamber relative to the tube.

3. A pump according to claim 1 or claim 2 in which the housing is formed of a cup shaped portion defining the rotatable chamber and an annular portion and the annular sheet has its outer portions secured to the rim of the cup shaped portion and has apertures through it for passage of fluid from the radially outer ends of the accelerating passages into the chamber.

4. A pump according to claim 3 in which the lining of the cup shaped portion abuts the lining of the annular portion and there is a fluid seal between the abutting surfaces.

5. A pump according to any preceding claim in which the corrosion resistant material is stainless steel.

6. A pump according to any preceding claim in which the material of high structural strength and of which the housing is formed is cast high tensile strength steel.

7. A pump according to claim 1 substantially as herein described with reference to the accompanying drawings.