JP2716823B2 - Pump operation control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pump operation control device applied to the operation of, for example, a cargo oil pump.

[Conventional technology]

Conventionally, for example, the operation control of a pump such as a cargo oil pump generally controls the rotation speed of a steam turbine or a variable speed electric motor of the driving machine automatically by a governor, and manually opens the discharge valve of the pump as needed. Is adjusted. In the former, the flow rate of the pump is
The flow rate is controlled by utilizing the characteristics of a pump whose total head is substantially proportional to the square of the rotation speed. In the latter, the flow rate is controlled by changing the resistance curve of the piping system of the pump by adjusting the opening of the discharge valve.

FIG. 2 is a characteristic curve diagram of a certain cargo oil pump. In the drawing, in general, when the value of the required suction head P exceeds the value of the effective suction head during operation of a pump such as a cargo oil pump, cavitation occurs in the impeller, and the total head H, the flow rate Q, and the efficiency of the pump rapidly increase. At the same time, the impeller and its surrounding members are eroded by noise and vibration. The required suction head P of the pump depends on the number of revolutions. For example, when the number of revolutions decreases, the flow rate decreases and the required suction head characteristics also shift to the low flow rate side. For this reason, there is a limit value of the flow rate at which stable operation cannot be performed, which is specific to the pump, corresponding to the rotational speed.

[Problems to be solved by the invention]

As described above, in a pump such as a cargo oil pump, when the value of the necessary suction head P exceeds the value of the effective suction head during operation, cavitation occurs in the impeller. At the same time, it moves to the low flow rate side. For this reason, when automatically controlling a pump such as a cargo oil pump on the basis of the number of rotations, when the flow rate reaches a limit value at which stable operation cannot be performed at a certain number of rotations, familiarity with the characteristics inherent to the pump and the piping system of the pump is made. The operator reduces the opening of the discharge valve and increases the resistance of the piping system so as to avoid operation in an unstable area, which requires skill and is complicated.

Also, in pumps such as cargo oil pumps,
So-called stripping is performed to pump cargo oil near the bottom of the inboard tank. When performing this stripping, the oil level in the ship's tank may drop, and the cargo oil pump may excessively suck in the air and gas in the ship's tank together with the cargo oil, making pumping impossible. The operation requires skill and is complicated.

[Means for solving the problem]

An operation control device for a pump according to the present invention has an object to solve the above problems, and has a suction tank provided on a suction side of a pump and a replacement chamber for separating gas from a pumped liquid provided on a discharge side of the pump. A recirculation valve for recirculating the pumped liquid in the replacement chamber to the suction tank; and a recirculation valve for the pump based on the input suction pressure and discharge pressure of the pump and the specific gravity of the pump liquid input in advance. The total head is calculated based on the previously input performance characteristics of the pump, the input rotation speed of the pump, and the total head height of the pump. The required suction head of the pump is set based on the rotation speed of the pump and the discharge flow rate of the pump. The input suction pressure of the pump and the specific gravity of the pump liquid previously input are input. The effective suction head of the pump is calculated based on the saturated vapor pressure at the temperature of the pump liquid, and the opening degree of the recirculation valve is calculated based on the input liquid level in the suction tank. The number of revolutions of the driving machine, the opening of the discharge valve of the pump, and the opening of the recirculation valve are adjusted to control the discharge flow rate of the pump and to suppress cavitation in the pump and optimal stripping in the suction tank. And a controller that performs the above operations together.

[Action]

That is, in the operation control device for a pump according to the present invention, a suction tank provided on the suction side of the pump, a replacement chamber provided on the discharge side of the pump for separating gas from the pumping liquid, and a pump pump in the replacement chamber are provided. A recirculation valve for refluxing the liquid to the suction tank, and the suction pressure and discharge pressure of the input pump
Adjusts the number of rotations of the pump driver, the opening of the discharge valve of the pump and the opening of the recirculation valve based on the rotation speed, the temperature of the pump liquid, the performance characteristics of the pump input in advance, and the specific gravity of the pump liquid. And a controller that performs
Based on the suction pressure and discharge pressure of the pump input to the controller and the specific gravity of the pump liquid input in advance, the total head of the pump is changed to the performance characteristics of the pump input in advance to the controller and the pump The controller calculates the discharge flow rate of the pump based on the rotation speed and the total head of the pump, and adjusts the rotation speed of the drive unit of the pump and the opening of the discharge valve of the pump. Controlled to quantitative.

Further, the necessary suction head of the pump is preliminarily input to the controller based on the performance characteristics of the pump input in advance to the controller, the pump rotation speed and the discharge flow rate of the pump. The controller calculates the effective suction head of the pump on the basis of the specific gravity of the pump liquid being pumped and the saturated vapor pressure at the temperature of the pump liquid being pumped, and the number of rotations of the pump drive unit and the opening of the discharge valve of the pump. Cavitation in the pump is suppressed by the controller adjusting the degree.

Also, the controller calculates the opening of the recirculation valve based on the liquid level in the suction tank input to the controller. When the liquid level in the suction tank drops and the pump sucks gas, the opening of the recirculation valve is calculated. Is controlled by the controller to return the pumped liquid in the replacement chamber to the suction tank, whereby the liquid level in the suction tank rises and optimal stripping in the suction tank is performed.

〔Example〕

FIG. 1 is a flow diagram of a cargo oil pump operation control device according to one embodiment of the present invention. The cargo oil pump has the performance characteristics shown in FIG. As shown in FIG. 1, the cargo oil pump operation control device according to this embodiment includes a controller 4 having a built-in micro CPU as shown in FIG. Detected by the sensors 2 and 3 and input to the controller 4. The controller 4 is connected to a main computer 5 on the ship, and the main computer 5 starts and stops the driving device 6 of the cargo oil pump 1 via the controller 4. Controller 4
, The suction temperature of the cargo oil detected by a temperature sensor (not shown) is transmitted via the line 7, and the saturation vapor pressure of the effective suction head is calculated by the micro CPU. Instead of performing this calculation, a saturated vapor pressure may be set and input in advance. A steam turbine or a variable-speed electric motor is used for the driving device 6. Also, the pressure sensor 3
May be used instead of the discharge pressure of the cargo oil pump 1 by using the pressure sensor 8 attached to the oil supply pipe 22 to the land tank to control the pump system as a whole. A command signal calculated by the micro CPU based on these input signals and a preset physical property value of the cargo oil is transmitted from the controller 4 to the drive unit 6 and the discharge valve 9 for flow rate adjustment, and the cargo oil pump 1 The rotation speed and the opening degree of the discharge valve 9 are automatically adjusted, and the control of the flow rate and the control of the cavitation suppression are performed.

Further, when the oil level of the cargo oil in the inboard tank 10 is lowered, the air or gas in the inboard tank 10 is sucked from the bell mouth 11 into the suction pipe 12 to form a two-phase fluid.
A suction tank 13 also serving as a suction strainer and a replacement chamber 18 are provided so that the phase fluid does not enter the cargo oil pump 1. In the suction tank 13, air and gas are separated from the cargo oil. Has become. The separated gas bypasses the cargo oil pump 1 and is sent to a land tank via a gas discharge line 14 and a check valve 15. Further, gas mixed into the liquid and sucked into the cargo oil pump 1 is also bypassed at the inlet of the impeller, and joins the discharge line 14 via the stop valve 16 and the check valve 17. Further, in the replacement chamber 18, the two-phase fluid is replaced by the upper layer gas and the lower layer cargo oil, and the cargo oil is returned to the suction tank 13 through the recirculation valve 19 through the recirculation line 20. I have. The recirculation valve 19 is also controlled by a command from the controller 4. That is, when the oil level in the suction tank 13 decreases and the cargo oil pump 1 sucks the gas, the recirculation valve 19 is automatically opened, and the cargo oil in the replacement chamber 18 is guided into the suction tank 13 to reduce the oil level. To rise. Reference numeral 21 denotes a main check valve installed in the oil supply pipe 22.

The controller 4 detects the suction pressure and the discharge pressure of the cargo oil pump 1 with the pressure sensors 2 and 3 and determines the cargo oil pump 1 based on a predetermined specific gravity of the cargo oil.
Is calculated by the micro CPU. The controller 4 has a function Q = f of the total head H and the flow rate Q shown in FIG.
(H) is input, and the flow rate Q is calculated by the micro CPU from the calculated total head H. Also, the flow rate Q
Similarly, the function P = f (Q) obtained by the trial operation is input to the relationship between the required suction head P and the required suction head P is calculated by the micro CPU from the calculated flow rate Q. Further, the effective suction head determines the micro pressure based on the suction pressure detected by the pressure sensor 2 and the predetermined specific gravity of the cargo oil and the saturated vapor pressure.
Computed by CPU. As these data previously input to the controller 4, data in the entire range of the number of rotations in which the number of rotations is used as a parameter may be input. However, since the software is complicated and expensive, FIG. Only the data at the rated rotation speed shown is input, and the characteristic that the flow rate Q of the cargo oil pump 1 is proportional to the rotation speed and the total head H and the necessary suction head P are proportional to the square of the rotation speed is used. The data at the rotation speed is corrected and calculated by the micro CPU according to the ratio between the rated rotation speed and the actual rotation speed detected by a tachometer (not shown). Then, based on these calculated values, the rotation speed of the driving machine 6, the opening of the discharge valve 9, and the opening of the recirculation valve 19 are automatically adjusted, and the flow rate of the cargo oil pump 1, cavitation suppression, stripping, etc. Is performed. In addition, the flow rate of the cargo oil pump 1 at the rotation speed and the comparison between the necessary suction head and the effective suction head are automatically performed, displayed on computer graphics, and recorded as necessary.

As described above, in the present apparatus, the rotation speed of the cargo oil pump 1 and the opening degrees of the discharge valve 9 and the recirculation valve 19 are automatically adjusted based on the calculation value of the micro CPU, thereby controlling the flow rate and suppressing cavitation. Since the control of the control and stripping is performed with high accuracy, the constant flow rate control and the stable operation in which the required suction head does not exceed the effective suction head become possible, and the energy saving operation in which the pressure loss due to the restriction of the discharge valve 9 is minimized. Thus, even when the throttle flow rate operation is performed for a long time, damage to the discharge valve 9 due to erosion is prevented, cavitation that occurs when the flow rate is excessively large is prevented, and continuous operation up to the minimum flow rate can be performed.

The operation control device for a pump according to the present invention is not limited to the above embodiment, and can be applied to the operation of a pump other than the cargo oil pump.

〔The invention's effect〕

The pump operation control device according to the present invention is configured as described above, and the controller calculates the total head of the pump and the discharge flow rate of the pump, and adjusts the rotation speed of the pump driving machine and the opening of the discharge valve of the pump. By doing so, the discharge flow rate of the pump is controlled to a predetermined amount, and the controller calculates the necessary suction head of the pump and the effective suction head of the pump, and adjusts the rotation speed of the drive unit of the pump and the opening of the discharge valve of the pump. This suppresses cavitation in the pump, the controller calculates the opening of the recirculation valve, and adjusts the opening of the recirculation valve to adjust the opening of the recirculation valve when the liquid level in the suction tank drops and the pump sucks gas. Reflux of the pumped liquid to the suction tank raises the liquid level in the suction tank and performs optimal stripping in the suction tank This enables automatic operation with the discharge flow rate of the pump maintained at a constant level, safe operation in which the required suction head does not exceed the effective suction head, and energy-saving operation of the pump that minimizes pressure loss due to the restriction of the discharge valve. Even when the pump is operated with the discharge flow rate reduced for a long time, erosion of the discharge valve of the pump due to the restriction is prevented, and cavitation generated at the time of excessive flow rate of the pump is prevented, and the flow rate is stabilized from a large flow rate to a minimum flow rate. Continuous operation of the pump becomes possible.

[Brief description of the drawings]

FIG. 1 is a flow diagram of an operation control device for a cargo oil pump according to an embodiment of the present invention, and FIG. 2 is a characteristic curve diagram of the cargo oil pump. 1 ... Cargo oil pump, 2,3,8 ... Pressure sensor, 4 ... Controller, 5 ... Main computer, 6 ... Driver, 9 ... Discharge valve, 10 ... Inboard tank, 11 ... Bell Mouse, 12 ... suction pipe, 13 ... suction tank, 14 ... discharge line, 18 ... replacement chamber, 19 ... recirculation valve, 20 ... recirculation line, 22 ... oil supply pipe.

Claims (1)

(57) [Claims] 1. A suction tank provided on a suction side of a pump, a replacement chamber provided on a discharge side of the pump for separating gas from a pumped liquid, and a pumped liquid in the replacement chamber being returned to the suction tank. A recirculation valve to be inputted, and the total head of the pump based on the input suction pressure and discharge pressure of the pump and the previously input specific gravity of the pumping liquid. The discharge flow rate of the pump based on the rotation speed of the pump and the total head of the pump is calculated based on the performance characteristics of the pump input in advance and the input rotation speed of the pump and the discharge flow rate of the pump. The necessary suction head of the pump is determined based on the input suction pressure of the pump, the specific gravity of the pump liquid input in advance, and the saturated vapor pressure at the temperature of the pump liquid input. The net positive suction head of the pump,
The opening degree of the recirculation valve is calculated based on the input liquid level in the suction tank, and the rotation speed of the drive unit of the pump, the opening degree of the discharge valve of the pump, and the opening degree of the recirculation valve are calculated. An operation control device for a pump, comprising: a controller that controls the discharge flow rate of the pump by adjusting the amount of cavitation, controls cavitation in the pump, and performs optimal stripping in the suction tank.