Novel driving control system of low-temperature liquid circulating pump

Abstract

The utility model relates to the technical field of low-temperature liquid circulating pumps, in particular to a novel driving control system of a low-temperature liquid circulating pump, which comprises a PLC (programmable logic controller) control unit, a servo motor driver, a servo motor, a low-temperature centrifugal pump, an inlet and outlet pipeline and an inlet and outlet pressure transmitter. The PLC control unit is used for starting and stopping the servo driver and switching various operation modes of the servo motor; the servo motor driver is used for driving and controlling the output of the rotating speed and the torque of the servo motor; the servo motor drives the low-temperature centrifugal pump to operate; signals of the inlet and outlet pressure transmitters are transmitted to the PLC control unit for system interlocking control protection. The servo motor is used for driving the low-temperature centrifugal pump, and compared with a traditional variable frequency motor for driving, the servo motor has the advantages of being high in response speed, easy to control, high in stability and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of low-temperature liquid circulation pumps, in particular to a novel drive control system for low-temperature liquid circulation pumps. Background Art

[0002] Cryogenic liquid pumps are special pumps used to transport cryogenic liquids in petroleum, air separation and chemical plants. They are used to transport cryogenic liquids from low-pressure places to high-pressure places. According to different working principles, cryogenic liquid pumps are mainly divided into plunger type and centrifugal type. Plunger type cryogenic liquid pumps are used in systems with high pressure and low flow; centrifugal type cryogenic liquid pumps are mostly used in systems with medium and low pressure and large flow.

[0003] The common drive control scheme for cryogenic centrifugal pumps at present: a three-phase inverter is connected to a three-phase asynchronous motor, which transmits power to the impeller through a transmission device and rotates it. When the turbine rotates, centrifugal force is generated, which sucks the cryogenic liquid from the pump inlet. As the impeller rotates, the cryogenic liquid is pushed to the pump outlet. As the torque of the impeller gradually increases, the pressure of the cryogenic liquid at the pump outlet also increases. When the outlet pressure reaches a certain level, the cryogenic liquid will enter the next process system.

[0004] The existing liquid circulation pump drive control system has low control accuracy and weak overload capacity. When the process requires increasing the flow rate of low-temperature liquid at the pump outlet, it is necessary to use a frequency converter to increase the motor power frequency to meet its overload capacity, which is insufficient. Utility Model Content

[0005] The utility model aims to at least improve one of the technical problems existing in the prior art. To this end, the utility model proposes a novel drive control system for a cryogenic liquid circulation pump.

[0006] According to the first aspect of the utility model, the driving control system of the novel cryogenic liquid circulation pump comprises a cryogenic centrifugal pump, an inlet pipeline and an outlet pipeline, wherein the cryogenic centrifugal pump is connected to a sealing gas inlet pipeline and a sealing gas control panel, a temperature sensor is provided in the cryogenic centrifugal pump for monitoring the sealing gas and bearing temperature in the cryogenic centrifugal pump, the temperature sensor is connected to the sealing gas control panel, the inlet pipeline and the outlet pipeline are both provided with a pressure transmitter, wherein the following is also included:

[0007] A PLC control unit, the PLC control unit is electrically connected to the pressure transmitter, and is used to receive current signals from the pressure transmitters on the inlet pipeline and the outlet pipeline, and the PLC control unit is electrically connected to the sealing gas control panel, and is used to receive the bearing temperature signal in the cryogenic centrifugal pump and interlock to control the start and stop of the bearing heater;

[0008] A servo motor driver, the servo motor driver is connected to the PLC control unit via a serial port communication, and is used to receive torque or speed given data sent by the PLC control unit to achieve quantitative control of the torque or speed;

[0009] A servo motor, wherein the servo motor is electrically connected to the servo motor driver, so that the PLC control unit can instantly control the servo motor through the servo motor driver;

[0010] A flow sensor is fixedly installed on the outlet pipeline and electrically connected to the PLC control unit to facilitate real-time collection of flow data in management to achieve the purpose of stabilizing the outlet flow.

[0011] According to the drive control system of the novel cryogenic liquid circulation pump of the embodiment of the utility model, a servo system composed of a servo motor driver and a PLC control unit is adopted to achieve the purpose of increasing the outlet liquid of the cryogenic liquid circulation pump. The servo control system based on the utility model has the following advantages:

[0012] 1. The control accuracy of the servo system is much higher than that of the inverter in the existing technology;

[0013] 2. The servo drive has a 3-fold overload capacity, which can be used to overcome the inertia moment of the inertial load at the moment of startup; while the frequency converter generally only allows 1.5-fold overload.

[0014] 3. The servo motor runs very smoothly at low frequency; the motor of the frequency conversion system has insufficient torque at low frequency and may vibrate.

[0015] 4. The servo system accelerates and decelerates quickly, and the servo motor can complete the change of speed in a very short time; the acceleration time of the variable frequency motor is related to the inertia of the motor shaft and the load. Generally, the greater the inertia, the longer the acceleration time. Therefore, the inverter motor accelerates and decelerates slowly. Compared with the inverter motor, the utility model has a better speed change performance.

[0016] 5. When the servo motor is suddenly loaded or unloaded, the motor speed does not fluctuate and there is almost no overshoot; while the motor of the frequency conversion system is greatly affected by the load, the utility model can effectively avoid the influence of the load.

[0017] In a possible implementation manner of the first aspect, the servo motor driver is externally connected to a three-phase power supply.

[0018] In a possible implementation manner of the first aspect, the temperature sensor is a platinum thermal resistor to facilitate output of a temperature signal.

[0019] In a possible implementation of the first aspect, the cryogenic centrifugal pump is provided with a bearing heater, and the bearing heater is electrically connected to the PLC control unit to facilitate adjusting the internal temperature of the cryogenic centrifugal pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 It is a control circuit diagram of a drive control system of a novel cryogenic liquid circulation pump according to an embodiment of the utility model;

[0022] Figure 2 This is a pin diagram of a PLC control unit of a drive control system of a novel cryogenic liquid circulation pump according to an embodiment of the utility model;

[0023] Figure 3 It is a pin diagram of a servo motor driver of a drive control system of a novel cryogenic liquid circulation pump according to an embodiment of the utility model.

[0024] Reference numerals:

[0025] PLC control unit 1, servo motor driver 2, servo motor 3, cryogenic centrifugal pump 4, inlet pipeline 5, outlet pipeline 6, flow sensor 7, sealing gas inlet pipeline 8, sealing gas control board 9. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0027] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0029] The terms "first", "second", "third", etc. in the specification and claims of the present application and the drawings are used to distinguish different objects rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a series of steps or units are included, or optionally, steps or units not listed are included, or optionally, other steps or units inherent to these processes, methods, products or devices are included.

[0030] Only the part relevant to the present application but not all content is shown in the accompanying drawings.Before discussing exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processing or methods described as flow charts.Although flow charts describe various operations (or steps) as sequential processing, many operations therein can be implemented in parallel, concurrently or simultaneously.In addition, the order of various operations can be rearranged.Described processing can be terminated when its operation is completed, but can also have additional steps not included in the accompanying drawings.Described processing can correspond to method, function, procedure, subroutine, subprogram etc.

[0031] As used in this specification, the terms "component", "module", "system", "unit", etc. are used to represent computer-related entities, hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a unit can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or distributed between two or more computers. In addition, these units can be executed from various computer-readable media having various data structures stored thereon. Units can communicate through local and / or remote processes, for example, based on signals having one or more data packets (e.g., data from a second unit interacting with another unit in a local system, a distributed system, and / or a network. For example, the Internet interacts with other systems via signals).

[0032] The control system of this application is mainly used in low-pressure, high-flow circulation systems in air separation equipment. For example, when the upper and lower towers are separated, the liquid oxygen at the bottom of the upper tower is sent to the main condenser evaporator at the top of the lower tower; the crude argon tower is divided into crude argon tower I and crude argon tower II, and a liquid argon pump is set between the two towers. Therefore, the control system will use a low-temperature centrifugal pump.

[0033] See also Figures 1 to 3As shown, the driving control system of the novel cryogenic liquid circulation pump of this embodiment includes a cryogenic centrifugal pump 4, an inlet pipeline 5 and an outlet pipeline 6. The cryogenic centrifugal pump 4 is connected to a sealing gas inlet pipeline 8 and a sealing gas control board 9. A temperature sensor is provided in the cryogenic centrifugal pump 4 to monitor the sealing gas and bearing temperature in the cryogenic centrifugal pump 4. The temperature sensor is connected to the sealing gas control board 9. The inlet pipeline 5 and the outlet pipeline 6 are both provided with a pressure transmitter, which also includes:

[0034] A PLC control unit 1, the PLC control unit 1 is electrically connected to the pressure transmitter, and is used to receive current signals from the pressure transmitters on the inlet pipeline 5 and the outlet pipeline 6, and the PLC control unit 1 is electrically connected to the sealing gas control panel 9, and is used to receive the bearing temperature signal in the cryogenic centrifugal pump 4 and interlock to control the start and stop of the bearing heater;

[0035] A servo motor driver 2, wherein the servo motor driver 2 is connected to the PLC control unit 1 via a serial port communication, and is used to receive torque or speed given data sent by the PLC control unit 1 to achieve quantitative control of the torque or speed;

[0036] A servo motor 3, wherein the servo motor 3 is electrically connected to the servo motor driver 2, so that the PLC control unit 1 can instantly control the servo motor through the servo motor driver 2;

[0037] The flow sensor 7 is fixedly mounted on the outlet pipe 6 and electrically connected to the PLC control unit 1 to facilitate real-time collection of flow data in management, so as to achieve the purpose of stabilizing the outlet flow.

[0038] According to the drive control system of the new cryogenic liquid circulation pump in the embodiment of the utility model, the purpose of increasing the outlet liquid of the cryogenic liquid circulation pump is achieved by adopting a servo system composed of a servo motor driver and a PLC control unit. The servo control system based on the utility model has high control accuracy, short response time and almost no overshoot phenomenon; the drive control system of the new cryogenic liquid circulation pump in the embodiment of the utility model has strong overload resistance and can adapt to more extreme working conditions; it can also operate smoothly under low-frequency conditions to meet the process requirements of low speed and low flow; in addition, in the speed mode, it can form a control closed loop with the outlet liquid flow signal to achieve the purpose of stabilizing the outlet flow; in the torque mode, it can form a control closed loop with the outlet liquid pressure signal to achieve the purpose of stabilizing the outlet pressure.

[0039] It should be noted that the servo motor driver 2 is externally connected to a three-phase power supply, and the servo motor driver can provide a three-phase power supply to the servo motor; the speed and torque of the servo motor can be effectively controlled by the servo motor driver.

[0040] It should be noted that the temperature sensor is a platinum thermal resistor, which is convenient for outputting temperature signals.

[0041] It should be noted that the cryogenic centrifugal pump 4 is provided with a bearing heater, and the bearing heater is electrically connected to the PLC control unit 1 to facilitate adjusting the internal temperature of the cryogenic centrifugal pump.

[0042] The drive control system of the novel cryogenic liquid circulation pump based on this embodiment provides the following two control modes:

[0043] 1. Speed ​​mode

[0044] The serial port communication of the interconnected PLC control unit 1 and the servo motor driver 2, the PLC control unit 1 transmits instructions to set the servo motor driver 2 to the speed mode. When the conditions for allowing the servo motor 3 to start are met, the operator can manually control the PLC control unit 1 to output the DO switch signal to the motor driver 2. The servo motor driver 2 puts the servo motor 3 in standby state. In this state, the operator can manually input the speed setting data into the PLC control unit 1, and the PLC control unit 1 outputs the speed setting data to the servo motor driver 2, and controls the speed of the servo motor 3 through the servo motor driver 2. According to the control characteristics of the servo motor 3, the given speed, actual speed and speed control output can form a closed-loop control, which makes the speed response time short and almost no overshoot. Thereby, the precise control of the speed of the cryogenic liquid circulation pump is achieved.

[0045] In addition, in the speed control mode, the drive control system of the new cryogenic liquid circulation pump can also realize closed-loop control of the outlet flow. The flow sensor 7 located on the outlet pipe 6 outputs a signal to the PLC control unit 1, and the PLC control unit 1 is used to form a closed loop of the outlet given flow, the outlet actual flow and the speed given data. Finally, the outlet flow of the cryogenic liquid circulation pump is kept stable.

[0046] 2. Torque mode

[0047] The serial port communication of the interconnected PLC control unit 1 and the servo motor driver 2, the PLC control unit 1 transmits instructions to set the servo motor driver 2 to the torque mode. When the conditions for allowing the servo motor 3 to start are met, the operator can manually control the PLC control unit 1 to output the DO switch signal to the servo motor driver 2. The servo motor driver 2 puts the servo motor 3 in standby state. In this state, the operator can manually write the torque given data to the PLC control unit 1, and the PLC control unit 1 transmits the torque given data to the servo motor driver 2, and controls the torque of the servo motor 3 through the servo motor driver 2. According to the control characteristics of the servo motor 3, the given torque, actual torque and torque control output can form a closed-loop control, which makes the torque response time short and almost without overshoot. Thereby, the precise control of the torque of the cryogenic liquid circulation pump is achieved.

[0048] In addition, in the torque control mode, the drive control system of the new cryogenic liquid circulation pump can also realize closed-loop control of the outlet pressure. The pressure transmitter on the outlet pipe 6 outputs a signal to the PLC control unit 1, and the PLC control unit 1 is used to form a closed loop of the outlet given pressure, the outlet actual pressure and the torque given data. Finally, the outlet pressure of the cryogenic liquid circulation pump is kept stable.

[0049] In the technical solution of the present utility model, the PLC control unit 1 will stop the driving linkage, including the following interlock parking conditions:

[0050] (1) Any command condition that does not satisfy the control system's interlocking conditions occurs;

[0051] (2) The inlet pressure transmitter of the inlet pipe 5 has low pressure;

[0052] (3) The outlet pressure transmitter of outlet pipe 6 has high pressure;

[0053] When any of the above conditions is triggered, the PLC control unit 1 interlocks the servo motor driver 2 to stop the servo motor 3 from running.

[0054] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the utility model.

[0055] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example.

[0056] Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Mentioning "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present embodiment application. The appearance of this phrase in various positions in the specification is not necessarily the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It can be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0057] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A novel drive control system for a cryogenic liquid circulation pump, comprising a cryogenic centrifugal pump (4), an inlet pipeline (5) and an outlet pipeline (6), wherein the cryogenic centrifugal pump (4) is connected to a sealing gas inlet pipeline (8) and a sealing gas control panel (9), a temperature sensor is provided inside the cryogenic centrifugal pump (4), and the temperature sensor is connected to the sealing gas control panel (9), and the inlet pipeline (5) and the outlet pipeline (6) are both provided with pressure transmitters, characterized in that: Also includes: A PLC control unit (1), the PLC control unit (1) being electrically connected to the pressure transmitter and used for receiving current signals from the pressure transmitters on the inlet pipeline (5) and the outlet pipeline (6), the PLC control unit (1) being electrically connected to the sealing gas control panel (9); A servo motor driver (2), the servo motor driver (2) being connected to the PLC control unit (1) via a serial port communication, and being used to receive torque or speed setting data sent by the PLC control unit (1) to achieve quantitative control of the torque or speed; A servo motor (3), wherein the servo motor (3) is electrically connected to the servo motor driver (2), so that the PLC control unit (1) can instantly control the servo motor through the servo motor driver (2); A flow sensor (7), wherein the flow sensor (7) is fixedly mounted on the outlet pipeline (6) and is electrically connected to the PLC control unit (1).

2. The driving control system of the novel cryogenic liquid circulation pump according to claim 1 is characterized in that: The servo motor driver (2) is externally connected to a three-phase power supply.

3. The driving control system of the novel cryogenic liquid circulation pump according to claim 1 is characterized in that: The temperature sensor is a platinum thermal resistor, which is convenient for outputting temperature signals.

4. The driving control system of the novel cryogenic liquid circulation pump according to claim 1 is characterized in that: The low-temperature centrifugal pump (4) is provided with a bearing heater, and the bearing heater is electrically connected to the PLC control unit (1).

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