Pulsationless duplex plunger pump and control method thereof

• US 4,808,077 A
• Filed: 01/06/1988
• Issued: 02/28/1989
• Est. Priority Date: 01/09/1987
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ishii, Mieko, Kan, Tsuneo, Nakamura, Yozo
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/141,218
• Time in Patent Office: 419 Days
• Field of Search: 417/2, 417/18, 417/22, 417/42, 417/43, 417/45, 417/53, 417/265
• US Class Current: 417/2
• CPC Class Codes: F04B 11/0058 with piston speed control
• CPC Class Codes: F04B 11/0075 connected in series

Abstract

Velocity control of two plungers provided in a pulsationless duplex plunger pump is effected by detecting pressure of a resultant discharge from the two plungers and positions of the plungers, and correcting sequentially a velocity instruction of the each plunger, based on pressure corresponding to the detected position of the each plunger so that the sum of velocities of the two plungers will be constant.

Claims

1. A pulsationless duplex plunger pump in which check valves are provided at a suction side and at a discharge side of one of two reciprocating pumps incorporated therein, said two reciprocating pumps being arranged in series and driven by electric drive motor means, and an outlet of said check valve at the discharge side communicates with the other incorporated pump, which comprises:

means for detecting pressure in a resultant liquid discharged from said two reciprocating pumps;

means for detecting a position of a plunger of each of said reciprocating pumps;

memory means for storing an instruction of a plunger velocity at every position of said each plunger;

means for correcting the instruction of the plunger velocity from said memory means, based on the pressure corresponding to the detected position of said each plunger so that the sum of velocities of said two plungers will be constant; and

means for controlling a velocity of each of said plungers according to corrected velocity instruction through a control of said electric drive motor means, wherein said velocity instruction correction is effected by adding a value proportional to a value obtained through reversing a sign of a time differential value of the pressure in said resultant discharged liquid.

2. A pulsationless duplex plunger pump in which check valves are provided at a suction side and at a discharge side of one of two reciprocating pumps incorporated therein, said two reciprocating pumps being arranged in series and driven by electric drive motor means, and an outlet of said check valve at the discharge side communicates with the other incorporated pump, which comprises:

means for detecting pressure in a resultant liquid discharged from said two reciprocating pumps;

means for detecting a position of a plunger of each of said reciprocating pumps;

memory means for storing an instruction of a plunger velocity at every position of said each plunger;

means for correcting the instruction of the plunger velocity from said memory means, based on the pressure corresponding to the detected position of said each plunger so that the sum of velocities of said two plungers will be constant; and

means for controlling a velocity of each of said plungers according to corrected velocity instruction through a control of said electric drive motor means, wherein said velocity instruction correction is effected by adding a value proportional to the sum of a value obtained by reversing a sign of a time differential value of the pressure in said resultant discharged liquid and a value proportional to a value obtained by subtraction of the detected pressure from a base line pressure.

3. A pulsationless duplex plunger pump in which check valves are provided at suction and discharge sides of one of two reciprocating pumps incorporated therein in series and driven by electric drive motor means, and an outlet of said check valve at the discharge side communicates with the other incorporated pump, which comprises:

means for detecting pressure in a resultant liquid discharged from said two pumps;

means for detecting a plunger position of each of said reciprocating pumps;

means for differentiating the detected pressure with respect to time to obtain a differential value of the pressure in the resultant discharged liquid;

means for obtaining a velocity instruction so that the sum of velocities of said two plungers becomes constant, based on the obtained pressure in the resultant discharged liquid and the detected plunger position;

means for correcting the velocity instruction by adding thereto a value proportional to a value obtained by reversing a sign of said differential value of the pressure; and

means for inputting the corrected velocity instruction into a plunger driver and controlling the velocity of said each plunger.

4. A pulsationless duplex plunger pump comprising:

a pair of reciprocating pumps fluidly connected with each other in series;

check valves provided at suction and discharge sides of one of said reciprocating pumps;

a pair of cams mounted on a shaft for reciprocating plungers of said reciprocating pumps at different speeds, respectively;

means for driving said shaft having said cams mounted thereon to rotate;

means for detecting pressure in a resultant liquid discharged from said two pumps;

means for detecting a plunger position of one of said plungers;

means for generating an electric instruction for plunger driving velocity, according to which said driving means is driven to reciprocate said plungers, based on a set value of flow rate required of said duplex plunger pump;

means for differentiating the detected pressure with respect to time to obtain a differential value of the pressure in the resultant liquid discharged from said reciprocating pumps;

means for correcting said electric instruction, by adding a value proportional to a value obtained through reversing a sign of the differential value of the pressure in the resultant discharged liquid at each plunger position; and

means for controlling said driving means according to the corrected electric instruction for plunger velocity.

5. A method of controlling a pulsationless duplex plunger pump having two reciprocating pumps in series and check valves provided at suction and discharge sides of one of said reciprocating pumps, said method comprising the steps of:

detecting a position of a plunger of one of said reciprocating pumps;

detecting pressure in a resultant liquid discharged from said two reciprocating pumps, the pressure to be detected corresponding to a position of said plunger;

calculating a valocity instruction based on a predetermined flow rate required of said duplex plunger pump and the plunger position and storing the velocity instruction;

differentating the detected pressure with respect to time to obtain a time-differential value of the pressure in the resultant discharged liquid;

correcting the stored velocity instruction based on the time-differential value of the pressure and the detected plunger position; and

controlling the reciprocating pumps by using the corrected velocity instruction so that a flow rate of the resultant liquid discharged from the reciprocating pumps is constant.

6. A method as defined in claim 5, wherein first correction of the velocity instruction is effected at a time earlier than a timing of the velocity instruction correction obtained through calculation based on the detected pressure and the detected plunger position, and after that the correction timing is shifted by a predetermined time with respect to the prior correction timing through judging whether or not there is a change in a position of occurrence of the pressure pulsation and whether or not there is a change in the sign of the positional signal.

7. A method as defined in claim 5, wherein said velocity instruction is corrected by adding a value proportional to a value obtained through reversing a sign of a time differential value of said discharged liquid pressure.

8. A method as defined in claim 5, wherein said velocity instruction correction is effected by adding a value proportional to the sum of a value obtained by reversing a sign of a time differential value of said discharged liquid pressure and a value proportional to a value obtained through subtraction of said detected pressure from a base line pressure.

9. A method of controlling a pulsationless duplex plunger pump in which check valves are provided at suction and discharge sides of one of two reciprocating pumps incorporated therein in series and driven by electric drive motor means, comprising the steps of:

detecting pressure in a resultant liquid discharged from said two pumps, said pressure to be detected corresponding to a position of each of said pumps;

correcting a stored velocity instruction of said each plunger from the detected pressure so as to make the sum of velocities of said two plungers constant; and

controlling a velocity of said each plunger based on a corrected velocity instruction, wherein said velocity instruction is corrected by adding a value proportional to a value obtained through reversing a sign of a time differential value of said discharged liquid pressure.

10. A method of controlling a pulsationless duplex plunger pump in which check valves are provided at suction and discharge sides of one of two reciprocating pumps incorporated therein in series and driven by electric drive motor means, comprising the steps of:

detecting pressure in a resultant liquid discharged from said two pumps, said pressure to be detected corresponding to a position of each of said pumps;

correcting a stored velocity instruction of said each plunger from the detected pressure so as to make the sum of velocities of said two plungers constant; and

controlling a velocity of said each plunger based on a corrected velocity instruction, wherein said velocity instruction correction is effected by adding a value proportional to the sum of a value obtained by reversing a sign of a time differential value of said discharged liquid pressure and a value proportional to a value obtained through subtraction of said detected pressure from a base line pressure.