Oil carry-over prevention from helium gas compressor

Abstract

The present invention provides a pumped helium circuit comprising a compressor ( 14 ) with a high pressure port ( 16 ) and a low pressure port ( 18 ) each connected to a supplied equipment ( 61,63,65,67 ) to respectively supply compressed helium to, and receive compressed helium from, the supplied equipment; a pressure relief valve ( 12 ) operable to link the high pressure port to the low pressure port in response to a predetermined pressure differential; a non-return valve ( 13 ) located between a low pressure side of the pressure relief valve and the supplied equipment; and means for preventing oil carry-over from the compressor to the supplied equipment.

1 . A pumped helium circuit comprising a compressor ( 14 ) with a high pressure port ( 16 ) and a low pressure port ( 18 ) each connected to a supplied equipment ( 61 , 63 , 65 , 67 ) to respectively supply compressed helium to, and receive compressed helium from, the supplied equipment; a pressure relief valve ( 12 ) operable to link the high pressure port to the low pressure port in response to a predetermined pressure differential; a non-return valve ( 13 ) located between a low pressure side of the pressure relief valve and the supplied equipment; and means for preventing oil carry-over from the compressor to the supplied equipment, characterised in that said means comprises means for preventing oil leaving the low pressure port and travelling towards the supplied equipment.  
   
   
       2 . A pumped helium circuit according to  claim 1 , wherein said means comprises an oil trap located in the circuit between the low pressure port and the supplied equipment.  
   
   
       3 . A pumped helium circuit according to  claim 1 , wherein said means comprises an oil adsorber located in the circuit between the low pressure port and the supplied equipment.  
   
   
       4 . A pumped helium circuit according to  claim 1 , wherein said means comprises a gas reservoir located in the circuit between the low pressure port and the supplied equipment.  
   
   
       5 . A pumped helium circuit according to  claim 1 , wherein said means comprises a combined gas reservoir and oil adsorber located in the circuit between the low pressure port and the supplied equipment.  
   
   
       6 . A pumped helium circuit according to  claim 1 , wherein said means comprises a pressure actuated switch in the circuit between the low pressure part and the supplied equipment, said switch being operable to stop operation of the compressor in response to a gas pressure at the low pressure port falling below a predetermined value, the predetermined value being less than the minimum pressure at the low pressure port during normal operation.  
   
   
       7 . A pumped helium circuit comprising a compressor ( 14 ) with a high pressure port ( 16 ) and a low pressure port ( 18 ) each connected to a supplied equipment ( 61 , 63 , 65 , 67 ) to respectively supply compressed helium to, and receive compressed helium from, the supplied equipment; and a pressure relief valve ( 12 ) operable to return compressed helium from the high pressure port to the compressor in response to a predetermined pressure differential; characterised in that the pressure relief valve is connected between the high pressure port and the compressor, independently of the low pressure port.  
   
   
       8 . A method for preventing oil carry-over from a helium compressor ( 14 ) to a supplied equipment ( 63 , 67 , 61 , 65 ) comprising the steps of 
 supplying compressed helium through a high pressure port ( 16 ) to the supplied equipment;    receiving compressed helium through a low pressure port ( 18 ) from the supplied equipment;    operating a bypass relief valve ( 12 ) in response to a differential pressure exceeding a predetermined value, thereby allowing oil-laden compressed helium to flow from the high pressure port to the compressor,    characterised in that the method further comprises the step of preventing oil from the oil-laden compressed helium from travelling from the low pressure port to the supplied equipment.