Method of removing stators from tubular stator housings

Abstract

A method of removing stators from tubular stator housings involving subjecting a tubular stator housing having an interior surface to which a worn stator is adhered by adhesive to cryogenic refrigeration until the stator shrinks and pulls away from the interior surface of the tubular stator housing.

What is claimed is: 
     
       1. A method of removing stators from tubular stator housings, comprising the steps of:
 placing a metal tubular stator housing having an interior surface to which a worn elastomer moineau-style stator is adhered by adhesive into a cryogenic refrigeration unit; 
 lowering the temperature in the cryogenic refrigeration unit gradually to cryogenic levels in order to avoid thermal shock to the tubular stator housing; 
 raising the temperature of the tubular stator housing gradually to ambient temperatures, the stator shrinking and pulling away from the interior surface of the tubular stator housing as the temperature is gradually lowered and then gradually raised. 
 
     
     
       2. The method as defined in  claim 1 , the tubular metal stator housing being subjected to temperatures between minus 150 degrees celcius and minus 200 degrees celsius. 
     
     
       3. The method as defined in  claim 1 , wherein the temperature in the cryogenic refrigeration unit is gradually decreased to cryogenic levels over a period of time of approximately 3 to 24 hours. 
     
     
       4. A method of removing stators from tubular stator housings, comprising the steps of:
 placing a tubular metal stator housing having an interior surface to which a worn elastomer moineau-style stator is adhered by adhesive into a cryogenic refrigeration unit; 
 lowering the temperature in the cryogenic refrigeration unit gradually to cryogenic levels in order to have the tubular metal stator housing and the stator shrink at substantially the same rate and avoid thermal shock, the temperatures in the cryogenic refrigeration unit reaching temperatures of between minus 150 degrees celsius and minus 200 degrees celsius; 
 raising the temperature in the cryogenic refrigeration unit gradually to ambient temperatures in order to avoid thermal shock, the stator shrinking and pulling away from the interior surface of the tubular stator housing as the temperature is gradually lowered and then gradually raised; and 
 exerting a force upon the stator to slide the stator out of the tubular stator housing. 
 
     
     
       5. The method as defined in  claim 4 , wherein the temperature in the cryogenic refrigeration unit is gradually decreased to cryogenic levels over a period of time of approximately 3 to 24 hours. 
     
     
       6. A method of removing an elastomer moineau-style stator adhesively adhered to an interior surface of a metal tubular stator housing, the method comprising the steps of: placing the metal tubular stator housing, having the stator adhesively adhered to the interior surface of the stator housing, into a cryogenic refrigeration unit; gradually lowering the temperature in the cryogenic refrigeration unit to a cryogenic temperature of between minus 150 degrees celsius and minus 200 degrees celsius so as to avoid thermal shock to at least the metal tubular stator housing and cause the metal tubular stator housing and the stator to shrink at substantially a same rate; allowing the stator, at the cryogenic temperature, to substantially separate from the interior surface of the tubular stator housing during the gradually lowering the temperature in the cryogenic refrigeration unit; and
 removing the stator from the housing following the gradually lowering the temperature in the cryogenic refrigeration unit.   
     
     
       7. The method of claim 6 further comprising the step of gradually lowering the temperature in the cryogenic refrigeration unit from a starting temperature of approximately minus 50 degrees celsius. 
     
     
       8. The method of claim 6 further comprising the steps of gradually raising the temperature of the tubular stator housing. 
     
     
       9. The method of claim 6 further comprising the step of gradually decreasing the temperature in the refrigeration unit at a rate of approximately 2.5 degrees celsius per minute. 
     
     
       10. The method of claim 6 further comprising the step of gradually decreasing the temperature in the refrigeration unit over a period of time of approximately 1 hour. 
     
     
       11. The method of claim 6 further comprising the step of gradually decreasing the temperature in the refrigeration unit to a temperature of approximately minus 196 degrees celsius.