Differential pressure controlled motor and pump barrier fluids pressure regulation system

Abstract

A motor and a pump barrier fluids pressure regulation system for a subsea motor and pump module is disclosed. The pressure regulation system comprises—a barrier fluid circuit ( 10 ) providing fluid flow communication from a hydraulic fluid supply ( 8 ) to a first cavity in the motor and pump module,—a pressure controlled flow control valve ( 9 ) controlling the supply of hydraulic fluid to the barrier fluid circuit ( 10 );—a second cavity arranged to receive hydraulic fluid from the hydraulic fluid supply via the first cavity, and—a pilot pressure circuit ( 11 ) comprising means for detecting and returning to the pressure controlled flow control valve ( 9 ) a differential pressure over a flow restriction ( 7; 13 ) connecting the first and second cavities.

1 . A motor and a pump barrier fluids pressure regulation system for a subsea motor and pump module ( 1 ), the pressure regulation system comprising:
 a barrier fluid circuit ( 10 ) providing fluid flow communication from a hydraulic fluid supply ( 8 ) to a first cavity in the motor and pump module,   a pressure controlled flow control valve ( 9 ) controlling a flow of hydraulic fluid from the hydraulic fluid supply to the barrier fluid circuit ( 10 );   a second cavity in selective fluid communication with the hydraulic fluid supply via the first cavity, and   a pilot pressure circuit ( 11 ) comprising means for detecting and returning to the pressure controlled flow control valve ( 9 ) a differential pressure over a flow restriction ( 7 ;  13 ) connecting the first and second cavities.   
     
     
         2 . The regulation system of  claim 1 , wherein a pump barrier fluid circuit ( 12 ) receives hydraulic fluid from a motor barrier fluid circuit ( 10 ) via a flow restriction ( 13 ) of fixed orifice diameter arranged externally of the motor and pump module ( 1 ), and over which the differential pressure is detected and returned to the pressure controlled flow control valve ( 9 ) that feeds hydraulic fluid into the motor and pump barrier fluid circuits in response to deviations from a predefined, desired pressure difference. 
     
     
         3 . The regulation system of  claim 1 , wherein said pressure controlled flow control valve ( 9 ) is one of a set of valves, including at least first and second valves ( 9 ,  14 ), which are arranged in parallel to feed hydraulic fluid into the motor barrier fluid circuit ( 10 ), and which are each responsive to the differential pressure over the flow restriction ( 7 ;  13 ), and further wherein said at least two pressure controlled flow control valves are individually responsive to separate ranges of the differential pressure over the flow restriction. 
     
     
         4 . The regulation system of  claim 3 , wherein in a set of first and second pressure controlled flow control valves the first valve ( 9 ) is set to open for hydraulic fluid flow into the motor barrier fluid circuit ( 10 ) in result of a differential pressure at or below a first predefined differential pressure at the flow restriction ( 7 ;  13 ), and the, second valve ( 14 ) is set to open for hydraulic fluid flow into the motor barrier fluid circuit ( 10 ) in result of a differential pressure at or below a second predefined differential pressure lower than the first predefined differential pressure. 
     
     
         5 . The regulation system of  claim 4 , wherein the first predefined differential pressure is about 5 bar, and the second predefined differential pressure is about 4.5 bar. 
     
     
         6 . The regulation system of  claim 2 , wherein in a set of first and second pressure controlled flow control valves the first valve ( 9 ) is sized for lower flow rates and the second valve ( 14 ) is sized for higher flow rates. 
     
     
         7 . The regulation system of  claim 6 , wherein the first valve ( 9 ) is sized for flow rates ranging down to about 0.3 l/min, and the second valve ( 14 ) is sized for flow rates ranging up to about 100 l/min or above. 
     
     
         8 . The regulation system of  claim 3 , wherein an ON/OFF valve is connected in series with the second pressure controlled flow control valve ( 14 ) of higher flow rate. 
     
     
         9 . The regulation system of  claim 1 , wherein a pressure controlled pressure relief valve ( 15 ) is arranged in parallel with the flow restriction ( 7 ;  13 ) to dump hydraulic fluid from the motor barrier fluid circuit ( 10 ) into the pump.