System and Method to Improve Operation of Hydraulic Pump for Subsea Service

Abstract

The operating performance and reliability of a pump, e.g. a hydraulic pump, can be significantly improved by incorporating an actively controlled positive displacement control valve in fluid communication with a fixed displacement pump, supply fluid line, and return fluid line. In use, the pump may be used to move fluid from the suction side to the discharge side of the pump, including fully opening the suction circuit to the pump cylinder and fully closing the pump discharge circuit during a pump suction stroke, fully closing the suction circuit and fully opening the pump discharge circuit to a downstream circuit during a pump discharge stroke, and allowing fluid to be pumped without the fluid passing through a valve spring loaded check valve.

1 . A system for pumping fluids subsea, comprising:
 a. a fixed displacement pump, the fixed displacement pump comprising:
 i. a drive cylinder, comprising a drive piston configured to be cyclically reciprocated by a separate hydraulic power unit and directional control valve; and 
 ii. a pumping cylinder, comprising a pumping piston configured to be cyclically reciprocated by the separate hydraulic power unit and directional control valve, the drive cylinder operatively linked to the pumping cylinder; 
   b. an inlet valve in fluid communication with the fixed displacement pump;   c. a supply fluid line in fluid communication with the inlet valve;   d. an outlet valve in fluid communication with the fixed displacement pump;   e. a return fluid line in fluid communication with the outlet valve;   f. an actively controlled positive displacement control valve in fluid communication with the fixed displacement pump, the supply fluid line, and the return fluid line;   g. a suction line port in fluid communication with the positive displacement control valve; and   h. a discharge line port in fluid communication with the positive displacement control valve.   
     
     
         2 . The system of  claim 1 , wherein the fixed displacement pump may be driven hydraulically, electrically, and/or mechanically. 
     
     
         3 . The system of  claim 1 , wherein the inlet valve and the positive displacement control valve may be controlled actively and/or passively and may further be operated hydraulically, electrically, and/or mechanically. 
     
     
         4 . The system of  claim 1 , further comprising an active controller operatively connected to the pump, the inlet valve, and the positive displacement control valve. 
     
     
         5 . The system of  claim 4 , wherein the active controller further comprises instrumentation adapted for providing feedback to the active controller. 
     
     
         6 . The system of  claim 5 , wherein the instrumentation further comprises a position sensor, a pressure sensor, a temperature sensor, a flow meter, or a sensor configured to aid in fluid qualitative analysis. 
     
     
         7 . The system of  claim 4 , wherein the positive displacement control valve comprises contamination resistant, hardened metal seal elements. 
     
     
         8 . The system of  claim 1 , wherein the drive cylinder is larger than the pumping cylinder. 
     
     
         9 . A method of improving operation of a subsea pump for a subsea service, comprising:
 a. disposing a pump subsea, the comprising:
 i. a fixed displacement pump, the fixed displacement pump comprising:
 1. a drive cylinder, comprising a drive piston configured to be cyclically reciprocated by a separate hydraulic power unit and directional control valve; and 
 2. a pumping cylinder, comprising a pumping piston configured to be cyclically reciprocated by the separate hydraulic power unit and directional control valve, the drive cylinder operatively linked to the pumping cylinder; 
 
 ii. an inlet valve in fluid communication with the fixed displacement pump; 
 iii. a supply fluid line in fluid communication with the inlet valve; 
 iv. an outlet valve in fluid communication with the fixed displacement pump; 
 v. a return fluid line in fluid communication with the outlet valve; 
 vi. an actively controlled positive displacement control valve in fluid communication with the fixed displacement pump, the supply fluid line, and the return fluid line; 
 vii. a suction line port in fluid communication with the positive displacement control valve; and 
 viii. a discharge line port in fluid communication with the positive displacement control valve; and 
   b. using the pump to move fluid from the suction side to the discharge side of the pump, moving comprising:
 i. during a pump suction stroke, fully opening the suction circuit to the pump cylinder and fully closing the pump discharge circuit; 
 ii. during a pump discharge stroke, fully closing the suction circuit and fully opening the pump discharge circuit to a downstream circuit; and 
 iii. allowing fluid to be pumped without the fluid passing through a valve spring loaded check valve. 
   
     
     
         10 . The method of  claim 9 , further comprising reducing suction pressure without needing to overcome a spring force in a suction check valve. 
     
     
         11 . The method of  claim 9 , further comprising not limiting the pump design by compression ratio. 
     
     
         12 . The method of  claim 9 , wherein the subsea service comprises preventing auto-siphoning of the fluid through a chemical metering pump in applications where discharge pressure is lower than suction pressure. 
     
     
         13 . The method of  claim 9 , further comprising synchronizing the operation of the positive displacement control valve with the pump operation. 
     
     
         14 . The method of  claim 9 , wherein the positive displacement control valve is configured to perform where conditions at the inlet valve or outlet valve are above or below ambient pressures in any combination. 
     
     
         15 . The method of  claim 9 , further comprising operating the positive displacement control valve hydraulically, electrically, or mechanically through a linkage to the pump drive mechanism. 
     
     
         16 . The method of  claim 9 , wherein the subsea service comprises using the positive displacement control valve where a pressure of a subsea production is lower than the minimum possible controllable delivery pressure of a topsides metering pump. 
     
     
         17 . The method of  claim 9 , wherein the subsea service comprises at least one of chemical injection into a fluid flowline, chemical metering, hydraulic fluid supply and power, pressure management, integrity testing, or blockage remediation. 
     
     
         18 . The method of  claim 9 , wherein:
 a. during the pump suction stroke, allowing fluid to flow through the pump suction port into the pump cylinder and drawing the fluid from a local reservoir or supply conduit by the movement of the pump piston; and   b. during the pump discharge stroke, pushing the fluid within the pump cylinder out of the pump by the pump piston and allowing the fluid to exit through the pump discharge port.   
     
     
         19 . The method of  claim 9 , wherein exiting fluid it is routed to a pipeline or tank.