JPH0281977A - Pump control device - Google Patents

Abstract

PURPOSE:To contrive the improvement of the operation characteristic and the rate of operation without generating a cavitation phenomenon by providing a suction pressure detecting means of a pump and a correcting means of a reference suction flow quantity by a suction pressure signal. CONSTITUTION:In a pump trip flow quantity setter 6, a pump trip flow quantity setting signal S2 is set so as to also increase when a speed signal S1 is increased. On the contrary, a pressure detector 10, set up in a suction line 3, detects a suction pressure of a pump 1, outputting this suction pressure signal S5 to a pressure compensator 11. During operation of the pump 1, when the suction pressure is decreased, vaporization of fluid is started in the pump 1 in a predetermined pressure or less, and a cavitation phenomenon is easily generated. Needless to say by correction, by the fact of the cavitation phenomenon being not easily generated with vaporization difficult when the suction pressure increases, the pressure compensator 11 is given the characteristic reducing a correction signal S6 being an output for an increase of the suction pressure signal S5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an operation control device for a general industrial boknob.

(Prior Art) Many pumps are used in industrial plants to suck up and pump fluid. This type of pump generally has a problem in that cavitation occurs near the internal impeller when the flow rate decreases. This cavitation phenomenon occurs near the inlet of the impeller where the pressure of the fluid is low due to the thickness of the blades, the angle of incidence, etc. At this time, when the pressure decreases to the saturated vapor pressure of the fluid, the fluid vaporizes and bubbles are generated. However, the bubbles are crushed by the impeller rotating at high speed, creating high impact pressure, which causes vibrations in the ME3 impeller and the pump, making it difficult to continue operating the pump. Since this kind of problem occurs when the amount of fluid 'a' is below a certain value, it is necessary to constantly monitor the pump so that the flow rate of the pump does not fall below a certain value.

FIG. 3 is an overall configuration diagram of a conventional pump control device. A pump 1 is connected to a motor 2 as a driving source, and is roughly connected to a suction line 3 and a discharge line 4. 3 to the discharge line 4. A speed detector 5 is installed in the 7-ri 2, and the output speed signal S1 is inputted to a pump trip flow rate setting device 6, and the pump trip flow rate setting device 6 sets a pump trip according to the speed signal $1. A flow rate setting signal S2 is output. Further, a flow rate detector 7 is installed in the suction line 3. The suction flow rate signal S3 output from the flow rate detector 7 and the pump trip flow rate setting signal S2 from the pump trip flow rate setting device 6 are compared in a comparator 8, and the suction flow rate signal 83 is the pump trip flow rate setting signal S2. When the value falls below this, it is determined that a cavitation phenomenon has occurred and there is a problem with continued operation of the pump 1, and the pump trip signal S4 is set to the interlock circuit 9.
Output to. When the pump trip signal S4 is input to the interlock circuit 9, an alarm (not shown) is used to alert the operator, and a signal to stop the motor 2 is output to perform a pump trip, thereby protecting the pump 1.

In general, as the rotation speed of the pump 1 increases, the cavidation phenomenon tends to occur more easily.
Pump trip flow FjkB2 constant signal S
2 is set to be large. However, as described above, this cavitation phenomenon is also related to the suction pressure of the pump 1, and as the suction pressure decreases, the fluid becomes more likely to vaporize, so the cavitation phenomenon becomes more likely to occur. Therefore, conventionally, in order to avoid the cavitation phenomenon, the setting 11a of the pump trip setting device 6 was set to the pump flow rate corresponding to the lowest value of the suction pressure due to the unique characteristics of the pump.

(Problem to be solved by the invention) If the set value of the pump trip flow rate is set to a value corresponding to the minimum suction pressure of the pump, cavidation phenomenon will not occur even if the suction pressure is high due to the characteristics of the pump. Nevertheless, when the suction flow rate decreases, a pump trip occurs, which causes the pump to be shut down even though it is safe and there is no problem with the pump, and the pump operation rate decreases. There was a problem. As a countermeasure to this problem, a bypass path or the like is provided to ensure a minimum flow rate of the pump, but this has the disadvantage that the device and its operation become complicated.

The present invention has been made in view of the above, and its purpose is to add a suction pressure signal to the setting of the pump trip flow rate in addition to the pump rotational speed and suction flow rate signal to generate the cavitation phenomenon. First, it is an object of the present invention to provide a pump control device that improves the operating characteristics and availability of the pump.

[Structure of the Invention] (Means for Solving the Problems) A reference suction flow rate setting means for setting a reference suction flow rate based on the rotational speed of the pump, a suction flow rate detection means for the pump, and a combination of the reference suction flow rate and the suction flow rate. A pump control device that controls the operation of the pump so that the suction flow rate does not fall below the reference suction flow rate by means of comparison means is provided with a pump suction pressure detection means and a correction means for the reference suction flow rate based on the suction pressure signal. Be equipped.

(Function) The suction pressure signal from the pressure detector is sent to the adder via a pressure compensator whose output decreases as the pressure increases, to the pump trip flow rate setting signal set based on the pump rotation speed. This signal is compared with the suction flow rate signal from the flow rate detector using a comparator to determine whether cavitation occurs even if the pump suction pressure is high and the suction flow rate is low. Within the range of the pump characteristics, the pump trip signal is not issued and normal operation is performed.

(Example) An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram. A pump 1 is connected to a motor 2, which is necessary as a drive source, and is roughly connected to a suction line 3 and a discharge line 4. Fluid flows from the suction line 3 to the discharge line 4. be swept away by A speed detector 5 is installed on the motor 2, and the output speed signal S1 is inputted to a pump trip flow rate regulator 6, which is a reference suction flow rate setting means, and the pump trip flow rate setter 6 receives the speed signal S1. A pump trip flow rate setting signal S2 corresponding to the pump trip flow rate setting signal S2 is output. Further, the suction line 3 is equipped with a flow rate detector 7 as a suction flow rate detection means and a pressure detector 10 as a suction pressure detection means. Of these, the suction pressure signal S5, which is the output of the pressure detector 10, is input to the pressure compensator 11, which is a correction means for the reference suction flow rate, which has a characteristic that the output signal decreases as the suction pressure increases. The correction signal S6 is output to the adder 12. The adder 12 adds the pump trip flow rate setting signal S2 from the pump trip flow rate setting device 6, and outputs the pump trip flow rate correction setting signal S7 to the comparator 8, which is a means for comparing the reference suction flow rate and the suction flow rate. . The comparator 8 uses this pump trip flow rate correction setting signal S7 and the suction flow rate signal S3 which is the output of the flow rate detector 7.
When the suction flow rate signal S3 is smaller than the pump trip flow rate correction setting signal S7, the pump trip signal S4 is output to the interlock circuit 9. The interlock circuit 9 is configured to operate an alarm (not shown) and output a signal to stop the motor 2 when the pump trip signal S4 is input.

Next, the action of structural acid F will be explained. When the motor 2 is operated, fluid flows from the suction line 3 to the discharge line 4 by the pump 1 . The pump trip flow rate setting device 6 inputs the speed signal S1 from the speed detector 5, and based on this speed signal S1, sieves out a flow rate that does not cause a cavitation phenomenon based on the characteristics of the pump, and outputs it as the pump trip flow rate setting signal S2. Output to adder 12. As the rotation speed of the pump 1 increases, the cavitation phenomenon becomes more likely to occur. Therefore, the pump trip flow rate setting device 6 should be set so that as the speed signal S1 increases, the pump trip flow rate setting signal S2 also increases. be.

On the other hand, a pressure detector 10 installed in the suction line 3 detects the suction pressure of the pump 1 and generates a suction pressure signal S.
5 is output to the pressure compensator 11. This is because if the suction pressure is reduced while the pump 1 is in operation, the fluid starts to vaporize within the pump 1 below a predetermined pressure, making it easier for cavitation to occur. Needless to say, the higher the suction pressure, the less likely it will be vaporized and the cavitation phenomenon will occur.
The correction signal S6, which is the output, has a characteristic of decreasing as the value increases. That is, as shown in the characteristic diagram of Fig. 2, conventionally, the pump trip flow ff when the pump suction pressure is ×2
According to the present invention, the 1iU constant value is Yl, but according to the present invention, when the pump suction pressure is less than or equal to . As a result, when the suction pressure is low and cavitation phenomenon easily occurs at pump suction pressure x 1, the pump trips at a pump trip flow rate setting value Y2 or less similar to the conventional pump, but when the suction pressure is high and cavitation phenomenon is difficult to occur, the pump trips. At suction pressure×2, the pump trip flow ff1g2 constant value is allowed to be as low as Yl. This correction signal S6 is added to the pump trip flow rate setting signal S2 from the pump trip flow rate setting device 6 in the adder 12, so if the suction pressure increases, the output of the adder 12 is the pump trip flow rate correction setting. Signal S7 decreases. This is because the pump trip flow rate set value has been lowered, and the comparator 8 compares the pump trip flow rate correction setting signal S7 that takes this suction pressure into consideration with the suction flow rate signal S3, and the suction flow rate signal S3 is If it is greater than the trip flow rate correction setting signal S7, there is no output and the pump 1 continues to operate. If the suction flow rate signal @S3 becomes smaller, a pump trip signal S4 is output to the interlock circuit 9, which activates an alarm (not shown) to notify the operator of the abnormality. At the same time, a signal to stop the motor 2 is issued to protect the pump 1.

As a result, as shown in Fig. 2, the operating range of the conventional pump is only Sea 7A, and the pump trips in zone B and zone C regardless of the suction flow rate, but in the present invention, the operating range is Spread over zones A and B, pump trips occur only in zone C. Furthermore, when the suction pressure is high and the caditation phenomenon is difficult to occur, the pump can be operated even in a small flow rate range, and the characteristics of the pump can be fully utilized.

[Effects of the Invention] As described above, according to the present invention, by setting an optimal pump trip flow rate correction setting signal for the suction pressure of the pump and monitoring and controlling the suction flow rate using this, the cavitation phenomenon peculiar to the pump can be suppressed. This has the effect of appropriately preventing the occurrence and improving pump operating efficiency and availability.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, FIG. 2 is an operating characteristic diagram, and FIG. 3 is an overall configuration diagram of a conventional pump control device. 1...Pump, 2...Motor, 3...
・Suction line, 4...Discharge line, 5...Speed detector, 6...Pump trip flow rate setting device, 7...Flow rate detector, 8...Comparator, 9...
Interlock circuit, 10...pressure detector, 12...adder.

Claims (1)

[Claims] Reference suction flow rate setting means for setting a reference suction flow rate based on the rotational speed of a pump that suctions, pressurizes and discharges fluid, suction flow rate detection means for detecting the suction flow rate of the pump, and comparing the reference suction flow rate and the suction flow rate. A pump control device that includes a comparison means and controls the operation of the pump so that the suction flow rate of the pump does not fall below the reference suction flow rate, the suction pressure detection means detecting the suction pressure of the pump, and the suction pressure that is the output of the suction pressure detection means. A pump control device comprising a correction means for correcting the reference suction flow rate based on a signal.