Multi-pressure compensation of variable displacement pump

• US 5,133,644 A
• Filed: 01/17/1991
• Issued: 07/28/1992
• Est. Priority Date: 01/17/1991
• Status: Expired due to Fees

• Current Assignee: Halliburton Company
• Original Assignee: Halliburton Company
• Inventors: Barr, Stephen W., Rice, Timothy D., Crump, Joseph B.
• Primary Examiner(s): Bertsch, Richard A.
• Assistant Examiner(s): Scheuermann, David W.
• Application Number:
  US07/642,482
• Time in Patent Office: 558 Days
• Field of Search: 417/218, 417/222 R, 417/53
• US Class Current: 417/218
• CPC Class Codes: F04B 2205/09 Flow through the pump
• CPC Class Codes: F04B 2207/0411 maximum
• CPC Class Codes: F04B 2207/0412 minimum
• CPC Class Codes: F04B 2207/0413 medium
• CPC Class Codes: F04B 2207/0421 maximum
• CPC Class Codes: F04B 2207/0422 minimum
• CPC Class Codes: F04B 2207/0423 medium
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: F04B 49/106 Responsive to pumped volume

Abstract

A variable displacement pump is controlled throughout a broad range of operating conditions between a maximum pressure, low flow rate combination and a minimum pressure, high flow rate combination even when the pump is driven by a power limited prime mover. Different relief valves set at different operating pressures are automatically selectably connected to a control port of the pump in response to the actual flow rate of the fluid pumped by the pump reaching different flow rate set points.

Claims

1. An apparatus for controlling a variable displacement pump having a pressure responsive control port, comprising:

pressure setting means for setting a selectable pressure limit at the pressure responsive control port;

flow select means for selecting a plurality of flow rates at which said pressure setting means is to be operated; and

control means for operating said pressure setting means to select a pressure limit for the pressure responsive control port in response to said flow select means and the actual flow rate of a flow from the pump.

2. An apparatus as defined in claim 1, wherein each of the plurality of flow rates of said flow select means is the flow rate defining a constant power output with a respective one of the selectable pressure limits of said pressure setting means.

3. An apparatus as defined in claim 1, wherein said pressure setting means includes:

a plurality of relief valves, each of said relief valves opening at a different respective pressure by which a respective pump operating pressure limit is defined;

a plurality of control valves, each of said control valves connected to a respective one of said relief valves, said control valves interconnected so that said control valves operate in unison in response to said control means; and

means for connecting said control valves to the control port of the pump.

4. An apparatus as defined in claim 3, wherein said means for connecting includes a primary valve operable in response to said control mean to close the control port of the pump when said primary valve is in a first position and to open the control port of the pump to said control valves when said primary valve is in a second position.

5. A pumping system for providing a pressurized fluid flow at pressure and flow rate combinations within the range between a maximum pressure, minimum flow rate combination and a minimum pressure, maximum flow rate combination, comprising:

a pressure compensated variable displacement pump having a pressure responsive control port;

a flow meter connected to an output of said pump;

valve means, connected to said control port of said pump, for defining a plurality of pressure limits for said control port; and

means, connected to said flow meter and said valve means, for operating said valve means to select which of said pressure limits is communicated with said control port of said pump in response to said flow meter indicating fluid is being pumped by said pump at one of a plurality of predetermined flow rates.

6. A pumping system as defined in claim 5, further comprising a prime mover connected to said pump, said prime mover providing a maximum power output less than the corner power which would be needed to provide the pressurized fluid at a maximum pressure, maximum flow rate combination.

7. A pumping system as defined in claim 6, wherein each of said predetermined flow rates is the respective flow rate requiring maximum power from said prime mover for the pressure limit to be communicated to said control port for flow rates less than that respective flow rate.

8. A pumping system as defined in claim 5, wherein said valve means includes:

a plurality of relief valves, each of said relief valves responding to a different respective maximum pressure; and

a plurality of control valves which communicate a selected one of said relief valves with said control port of said pump in response to said operating means.

9. A pumping system as defined in claim 8, wherein said operating means includes:

means for entering a plurality of flow rate set points defining the flow rates at which said operating means selects which of said relief valves is communicated with said control port of said pump; and

means for comparing said set points with the actual flow rate received from said flow meter for determining when a different relief valve is to be communicated with said control port.

10. A method of operating a variable displacement pump within the power limits of a prime mover but throughout a range of pressure-flow rate combinations, comprising:

monitoring the flow rate of a flow pumped by the variable displacement pump; and

limiting the maximum pressure at which the pump pumps the flow in response to the monitored flow rate, wherein limiting the maximum pressure includes;

selecting a plurality of flow rate set points at which the pump is to be limited to different respective maximum pressures;

determining when the monitored flow rate equals one of the selected flow rate set points; and

communicating one of a plurality of relief valves with a control port of the pump in response to determining the monitored flow rate equals one of the selected flow rate set points, each of the relief valves responsive to a different maximum pressure.

11. A method as defined in claim 10, wherein each selected flow rate set point is the maximum flow rate within the power limit of the prime mover for the previously set maximum pressure.

12. A method of operating a variable displacement pump within the power limits of a prime mover but throughout a range of pressure-flow rate combinations, comprising:

monitoring the flow rate of a flow pumped by the variable displacement pump; and

limiting the maximum pressure at which the pump pumps the flow in response to the monitored flow rate, wherein limiting the maximum pressure includes;

setting the pump to operate up to a first maximum pressure;

determining when the monitored flow rate equals the flow rate at which the power limit of the prime mover is reached for the first maximum pressure; and

resetting the pump to operate up to a second maximum pressure less than the first maximum pressure.

13. A method as defined in claim 12, wherein limiting the maximum pressure further includes repeating said determining and resetting for the second and additional sequentially smaller maximum pressures down to a last maximum pressure so that the pump provides flows at pressure and flow rate combinations between the first maximum pressure at a minimum flow rate and the last maximum pressure at a maximum flow rate.

14. A method of operating a variable displacement pump within the power limits of a prime mover but throughout a range of pressure-flow rate combinations, comprising:

monitoring the flow rate of a flow pumped by the variable displacement pump; and

limiting the maximum pressure at which the pump pumps the flow in response to the monitored flow rate, wherein limiting the maximum pressure includes operating the pump at a higher maximum pressure until the monitored flow rate reaches the flow rate at which the power limit of the prime mover is reached and then operating the pump at a lower maximum pressure.