Pump casing with pre-stressed lining

Abstract

A method is described for forming a lining on an inner surface of a pump casing. The lining can protect the pump casing from corrosive and abrasive fluids. The method disclosed improves the durability and reliability of the lining by introducing a compressive pre-stress to the lining when the casing is not loaded such that during normal operation, the lining can be in a stress state near neutral and avoid failures related to excessive tensile strains. The method includes securing at least a portion of the casing in a stationary position and applying an external load to deform the casing. The method further includes depositing the lining onto the inner surface of the casing, curing the lining, and removing the external load to pre-stress the lining.

What is claimed is: 
     
         1 . A method for forming a lining on an inner surface of a pump casing, the method comprising:
 securing at least a portion of the casing in a stationary position;   applying an external load to deform the casing;   depositing the lining onto the inner surface of the casing;   curing the lining; and   removing the external load to pre-stress the lining.   
     
     
         2 . The method of  claim 1 , wherein curing the lining comprises:
 adhering the lining to the inner surface of the casing; and   solidifying the lining such that the lining becomes compressed when the external load is released.   
     
     
         3 . The method of  claim 1 , further comprising:
 roughening the inner surface; and   treating the inner surface with a bonding agent to facilitate the lining adhering to the casing.   
     
     
         4 . The method of  claim 1 , wherein curing the lining further comprises applying a load to the lining such that the lining is compressed when the lining is cured. 
     
     
         5 . The method of  claim 1 , wherein curing the lining further comprises inducing a compressive stress as the lining solidifies. 
     
     
         6 . The method of  claim 1 , wherein applying the external load is performed prior to curing the lining. 
     
     
         7 . The method of  claim 1 , wherein curing the lining is performed prior to applying the external load. 
     
     
         8 . The method of  claim 1 , wherein depositing the lining comprises depositing a silicon carbide polymer onto the inner surface of the casing. 
     
     
         9 . The method of  claim 1 , wherein depositing the lining comprises depositing at least one of a rubber, a resin, a polymer, and a ceramic composite onto the inner surface of the casing. 
     
     
         10 . The method of  claim 1 , wherein the casing encloses an impeller, propeller, or rotor of the pump and is subject to fluctuating fluid pressure having a maximum operation load. 
     
     
         11 . The method of  claim 10 , wherein the external load corresponds to the maximum operation load exerted on the casing during operation of the pump. 
     
     
         12 . The method of  claim 1 , wherein applying the external load comprises bending the casing. 
     
     
         13 . The method of  claim 1 , wherein applying the external load comprises applying a pressure differential between the inner surface and an outer surface of the casing. 
     
     
         14 . The method of  claim 1 , wherein applying the external load comprises bending the casing and applying a pressure differential between the inner surface and an outer surface of the casing. 
     
     
         15 . The method of  claim 1 , wherein depositing the lining further comprises:
 providing a mold;   positioning the mold to form a gap between the mold and the inner surface of the casing; and   filling the gap with the lining at a predetermined pressure that induces a pre-stress in the casing.   
     
     
         16 . The method of  claim 1 , wherein depositing the lining comprises forming a layer of material having a thickness between about 4 mm and 50 mm. 
     
     
         17 . A pump comprising:
 a casing assembly for enclosing a pumping element, the casing assembly having an inner surface; and   a lining adhered to the inner surface of the casing assembly, the lining compressively pre-stressed by the casing assembly to withstand cyclic stresses and is formed of an anti-corrosive or anti-abrasive material to reduce corrosion or increase wear resistance.   
     
     
         18 . The pump of  claim 17 , wherein the casing assembly comprises a first casing half and a second casing half, wherein the first casing half includes a first lining adhered to the first casing half and the second casing half comprises a second lining adhered to the second casing half, the first and second linings being compressively pre-stressed. 
     
     
         19 . The pump of  claim 17 , wherein the pumping element comprises an impeller, a propeller, or a rotor. 
     
     
         20 . The pump of  claim 17 , wherein the first and the second lining is formed of a silicon carbide polymer. 
     
     
         21 . The pump of  claim 17 , wherein the first and second linings comprise one of a rubber, a resin, a polymer, and a ceramic composite. 
     
     
         22 . The pump of  claim 17 , wherein the first and second linings each comprise a layer of material having a thickness between about 4 mm and 50 mm. 
     
     
         23 . The pump of  claim 17 , wherein the first casing half and a second casing half further comprise an intake and an outlet. 
     
     
         24 . A casing enclosing a pumping element for pumping fluids, the casing comprising:
 a metal structure having an inner surface facing the pumping element; and   a lining overlaying the metal structure for protecting the metal structure from corrosion or abrasion, wherein the lining forms a uniform layer compressively pre-stressed when the metal structure is under an unloaded condition.   
     
     
         25 . The casing of  claim 24 , wherein the lining comprises a silicon carbide polymer. 
     
     
         26 . The casing of  claim 24 , wherein the lining comprises a layer of material having a thickness between about 4 mm and 50 mm.