Screw pump rotors and ring seals for screw pump rotors

Abstract

A pump rotor for a screw pump, comprising a shaft, a thread on the shaft, the thread comprising a groove disposed on an outer surface thereof, and a seal disposed in the groove. The seal and the groove are configured to retain the seal in the groove while allowing radial displacement of the seal with respect to the thread as the pump rotor is deflected.

1 . A pump rotor for a screw pump, comprising:
 a shaft;   a helical thread on the shaft, the thread comprising a groove disposed on an outer surface thereof, and   a seal disposed in the groove, wherein the seal and the groove are configured to retain the seal in the groove while allowing radial displacement of the seal with respect to the thread as the pump rotor is deflected.   
   
   
       2 . The pump rotor of  claim 1 , wherein the seal is a ring seal. 
   
   
       3 . The pump rotor of  claim 2 , wherein the ring seal is configured to protrude outwardly from the groove and to rest against an inner surface of a liner of the screw pump. 
   
   
       4 . The pump rotor of  claim 3 , wherein the ring seal and the groove are configured to enable slip flows from beneath the ring seal. 
   
   
       5 . The pump rotor of  claim 3 , wherein the ring seal is configured to rotate with the shaft. 
   
   
       6 . The pump rotor of  claim 5 , further comprising: a first and a second pins disposed in the groove, wherein the ring seal is disposed between the first and second pins. 
   
   
       7 . The pump rotor of  claim 6 , wherein the ring seal and the thread are helical. 
   
   
       8 . The pump rotor of  claim 1 , further comprising a plurality of pins disposed in the groove and the seal comprises a plurality of ring seals, wherein each of the plurality of ring seals is disposed between a pair of the consecutive pins. 
   
   
       9 . The pump rotor of  claim 3 , wherein the ring seal is a sacrificial wear component of the pump rotor and the ring seal and the groove are configured to prevent the ring seal from getting dislodged from the groove even after the ring seal is worn out. 
   
   
       10 . The pump rotor of  claim 3 , wherein groove and the ring seal comprise an inverted T-shape cross-section. 
   
   
       11 . The pump rotor of  claim 3 , wherein ring seal and the groove comprise a cross-section that is a mirror image of L-shape cross-section. 
   
   
       12 . The pump rotor of  claim 3 , wherein the ring seal and the groove are of dovetail-shape cross-section. 
   
   
       13 . The pump rotor of  claim 3 , wherein a low pressure side of the ring seal and a corresponding side of the groove that is facing the low pressure side of the ring seal are configured to decrease the contact forces between the ring seal and an inner surface of a liner of the screw pump. 
   
   
       14 . A method of reducing slip flow in a screw pump having a casing having a low-pressure inlet and a high-pressure outlet, a liner disposed inside of the casing, and a rotor disposed inside of the liner having a shaft and a thread disposed on an outer surface of the shaft, the method comprising:
 forming a groove on outer surface of the thread; and   disposing a ring seal in the groove such that the ring seal protrudes outwardly from the groove and rests against an inner surface of the liner of the screw pump to reduce the slip flow from the high-pressure outlet to the low-pressure inlet, the ring seal and the groove being configured to retain the seal in the groove while allowing radial displacement of the seal with respect to the thread as the pump rotor is deflected.   
   
   
       15 . The method of  claim 14 , wherein the ring seal and the groove are configured to enable slip flows from beneath the ring seal. 
   
   
       16 . The method of  claim 14 , wherein the groove is formed varying in depth. 
   
   
       17 . The method of  claim 14 , further comprising enabling the ring seal to rotate as the shaft is rotated. 
   
   
       18 . A twin screw pump, comprising:
 a casing having an inlet and an outlet;   a liner disposed inside of the casing; and   at least two rotors disposed inside of the liner, each rotor comprising,
 a shaft; 
 a thread disposed on a portion of an outer surface of the shaft; 
 a groove on an outer surface of the thread; and 
 a ring seal in the groove and configured to rotate with the shaft and to protrude outwardly from the groove, wherein the ring seal and the groove are configured to retain the seal in the groove while allowing radial displacement of the seal with respect to the thread as the pump rotor is deflected. 
   
   
   
       19 . The pump of  claim 18 , wherein the ring seal and the groove are configured to enable slip flows from beneath the ring seal. 
   
   
       20 . The pump of  claim 18 , wherein a low pressure side of the ring seal and a corresponding side of the groove that is facing the low pressure side of the ring seal are configured to decrease the contact forces between the ring seal and an inner surface of a liner of the screw pump. 
   
   
       21 . A rotor for a screw pump comprising:
 a shaft;   a helical thread disposed on an outer surface of said shaft, said helical thread defining a groove therein;   a seal structure lockingly disposed within said groove, wherein said seal and said groove are configured to allow radial displacement of the seal with respect to the thread as the rotor is deflected.