Durable pumps for abrasives

Abstract

Durable pumps for abrasives are provided. An example centrifugal pump stage for subsurface operation has a thrust washer located inside the circumference of an outboard clearance seal between an impeller shroud and the diffuser. Relocation of the thrust washer allows the clearance seal to protect the thrust washer from abrasives. A centrifugal action of an outboard seal lip effects a separation of the particles from the fluid nearest the gap of the outboard seal and drives the particles away from the gap of the outboard seal. When an abrasive particle in the leakage flow does clear the outboard seal, the particle is readily flushed across the thrust washer by the leakage flow to the central fluid inlet to prevent wear of the thrust washer. In an implementation, the inside diameter of the thrust washer is approximately flush with the bore of a central fluid inlet of the pump stage.

1 . A pump stage for application in a subsurface hydrocarbon well, comprising:
 a diffuser;   an impeller;   a thrust washer; and   an outboard seal formed between a surface of the impeller and a first surface of the diffuser and located radially outward from an outside periphery of the thrust washer with respect to a central axis of the pump stage.   
     
     
         2 . The pump stage of  claim 1 , wherein the outboard seal protects a pump component from particles in a leakage flow of a fluid being pumped, wherein the pump component is selected from a group consisting of the thrust washer and a balance ring seal. 
     
     
         3 . The pump stage of  claim 1 , further comprising an outboard seal lip of the impeller;
 wherein a surface of the outboard seal lip at an outside diameter of the outboard seal lip engages a second surface of the diffuser to prevent particles in a fluid being pumped from bypassing a centrifugal action of the outside periphery of the outboard seal lip.   
     
     
         4 . The pump stage of  claim 3 , wherein when the impeller rotates a centrifugal action of the outboard seal lip impels a fluid near a gap of the outboard seal to move radially outward from the gap of the outboard seal; and
 wherein when the fluid contains particles the centrifugal action of the outboard seal lip effects a separation of the particles from the fluid nearest the gap of the outboard seal and drives the particles away from the gap of the outboard seal.   
     
     
         5 . The pump stage of  claim 1 , wherein a gap of the outboard seal and a clearance around the thrust washer form a path for a leakage flow comprising a fluid flow from the impeller back to a central fluid inlet of the pump stage;
 wherein the outboard seal restricts the leakage flow through the path more than the clearance around the thrust washer restricts the same leakage flow; and   wherein when a particle in the leakage flow follows the path and clears the outboard seal the particle is readily flushed across the thrust washer by the leakage flow to the central fluid inlet to prevent a wear of the thrust washer.   
     
     
         6 . The pump stage of  claim 1 , wherein an inside diameter of the thrust washer is approximately flush with an outside diameter of a central fluid inlet of the pump stage; and
 wherein the outboard seal is approximately flush with an outside diameter of the thrust washer.   
     
     
         7 . The pump stage of  claim 1 , wherein an inside cylindrical surface of the thrust washer at an inside diameter of the thrust washer is flush with a bore of a fluid inlet of the pump stage. 
     
     
         8 . The pump stage of  claim 7 , wherein the inside cylindrical surface of the thrust washer is in contact with fluid in the fluid inlet of the pump stage. 
     
     
         9 . The pump stage of  claim 1 , wherein a diameter of the outboard seal determines a volume of a first fluid cavity on a first side of the impeller to equalize a first fluid pressure on the first side of the impeller with a second fluid pressure on a second side of the impeller; and
 wherein equalizing the fluid pressures on the first side and the second side of the impeller reduces a friction of the impeller on the thrust washer.   
     
     
         10 . The pump stage of  claim 9 , wherein the diameter of the outboard seal is reduced in order to equalize the fluid pressures on the first side and the second side of the impeller; and
 wherein a diameter of the thrust washer is reduced to less than an inside diameter of the outboard seal.   
     
     
         11 . The pump stage of  claim 10 , wherein the reduced diameter of the thrust washer and a consequent reduced surface area of the thrust washer reduces an overall friction of the impeller on the thrust washer. 
     
     
         12 . The pump stage of  claim 10 , wherein the reduced diameter of the thrust washer reduces a moment arm of a braking torque acting between the impeller and the thrust washer. 
     
     
         13 . An impeller for a submersible pump for subsurface pumping of a fluid, comprising:
 a circular pump component at a first radius from a center of rotation of the impeller; and   a surface radially outboard of the circular pump component and at a second radius greater than the first radius, the surface forming an outboard seal with a diffuser at the second radius to protect the circular pump component from particles in a leakage flow of the fluid being pumped.   
     
     
         14 . The impeller of  claim 13 , wherein the circular pump component is selected from a group consisting of a thrust washer and a balance ring seal. 
     
     
         15 . The impeller of  claim 13 , further comprising a lip on the impeller, the lip possessing multiple surfaces engaging the diffuser including the surface forming the outboard seal;
 a first surface of the lip to engage a first surface of the diffuser to form the outboard seal;   a second surface of the lip radially outward from the first surface of the lip, the second surface to engage a second surface of the diffuser to impel the fluid away from a gap opening of the outboard seal; and   wherein when the fluid contains particles a centrifugal action of the second surface of the lip drives the particles away from the gap opening of the outboard seal.   
     
     
         16 . The impeller of  claim 15 , wherein when the lip rotates with the impeller, a centrifugal action of the second surface of the lip causes a separation of the particles away from the fluid nearest the gap opening of the outboard seal. 
     
     
         17 . The impeller of  claim 15 , wherein when the lip rotates with the impeller, the lip impels the fluid in a circular motion; and
 wherein when the fluid contains particles a centrifugal force imparted by the circular motion separates the particles away from the fluid nearest the gap opening of the outboard seal.   
     
     
         18 . The impeller of  claim 14 , wherein a gap opening of the outboard seal and a clearance between the thrust washer and the diffuser form a path for a leakage flow in the submersible pump from the impeller back to a central fluid inlet of the submersible pump;
 wherein a centrifugal action of the lip restricts the leakage flow through the path more than the clearance between the thrust washer and the diffuser restricts the same leakage flow; and   wherein when a particle in the leakage flow follows the path and clears the outboard seal the particle is readily flushed across the thrust washer by the leakage flow to the central fluid inlet to prevent a wear of the thrust washer.   
     
     
         19 . A method, comprising:
 constructing a centrifugal pump stage for a multi-stage submersible pump for a subsurface hydrocarbon well, the pump stage including an impeller, a diffuser, and a thrust washer; and   locating the thrust washer radially inboard in relation to an impeller-to-diffuser clearance seal of the pump stage.   
     
     
         20 . The method of  claim 19 , further comprising constructing an impeller projection to engage multiple surfaces of the diffuser;
 wherein a first surface of the impeller projection engages a first surface of the diffuser to form the impeller-to-diffuser clearance seal;   wherein a second surface of the impeller projection engages a second surface of the diffuser to accelerate a circular motion of a fluid near a gap of the impeller-to-diffuser clearance seal; and   wherein when the fluid contains particles a centrifugal force imparted by the circular motion separates the particles away from the gap.