JPS5979082A - Operation test for lng pump - Google Patents

Abstract

PURPOSE:To estimate an actual performance curve of the pump from the performance curve obtained by the test and bring the temperature condition of parts in the pump to the closed condition to the actual operation by a method wherein the operation test is effected by using liquid nitrogen and reducing the revolving number of the pump. CONSTITUTION:When the operation test of the LNG pump 1 is effected, a motor is driven in the frequency of an electric source, which is lower than the same predetermined for the motor. In this case, the amount of delivery of the liquid nitrogen, used for this test, is measured by a flow meter 7 and the delivery pressure P thereof is measured by a pressure gauge 9 while the performance curve, in which the amount Q of delivery is smaller than a predetermined flow amount, is obtained since the rotating number of the motor is lower than the predetermined rotating number for the same. However, the number of pump vanes is not necessary to be reduced since the motor will never be overloaded, and the parts of the pump are not necessary to be exchanged since the boiling point of the LNG is not different so much from the same of the liquid nitrogen. Accordingly, the actual performance curve may be estimated correctly from the performance curve obtained in this test while the operation test may be effected in a closed condition to the actual operation in the temperature condition of the parts in the pump.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for conducting an operational test of an LNG pump using liquid nitrogen and reducing the rotational speed of the pump.

Obtaining LNG is difficult for small domestic users, and for this reason, LNG pump manufacturers
It is difficult to test the operation of the pump using

Therefore, conventionally, LPG or liquid nitrogen (LN2) has been used for operational tests.

On the other hand, LNG pumps are designed taking into account the contraction of each part due to liquid temperature, but since the boiling point of LPG is significantly higher than that of LNG, it is difficult to conduct operational tests using LPG. If you do so, you will need to replace some of the parts with Haku parts.

Therefore, this is different from the actual operating condition of the LNG pump, and although the performance curve can be obtained relatively accurately, some parts inside the LNG pump are used at a temperature different from the actual operation, and the actual operation is simulated. It doesn't matter.

In addition, if the fluid subjected to the operational test is liquid nitrogen, the boiling point is not much different from the boiling point of LNG, so there is no problem with the temperature condition of the internal parts of the pump, but since the specific gravity is about twice that of LNG,
When a predetermined flow rate of liquid nitrogen is discharged from the pump, the motor becomes overloaded. Therefore, in order to avoid overloading, an operation test is conducted by handling some of the pump blades and rotating the motor at the regular rotation speed. Estimating the performance curve at a certain time will result in a large error.

In view of this, the present invention is designed to simulate the actual operating conditions of an LNG pump as much as possible, estimate a highly reliable performance curve, and bring the temperature of the internal parts of the pump to a state close to the actual state. It was created with the purpose of

5) Embodiments of the present invention will now be explained with reference to the drawings.

A suction pipe 3 and a discharge pipe 4 are connected to a pump pot 2 capable of accommodating an LNG pump 1 for operation test, and the suction pipe 3 is connected to the bottom side of a tank 5 containing liquid nitrogen, and the discharge pipe 4 is connected to the upper space of the tank 5, and a flow rate control valve 6 and a flow meter 7 are provided in the middle of the discharge pipe 4.

Further, in the figure, 8 is a power cable, 9 is a pressure gauge, and 10 is a pipe line for discharging nitrogen gas from the tank 5 into the atmosphere or sending it to another recovery device.

During an operation test of the LNG pump, the motor is driven by setting the frequency of the power source to a frequency lower than the predetermined frequency of the motor.

Therefore, the LNG pump 1 is driven at a rotation speed lower than a predetermined rotation speed, and liquid nitrogen passes from the tank 5 through the suction pipe 3.
It flows into the LNG pump 1 from the pump pot 2, is pressurized by the LNG pump 1, and is returned to the tank 5 through the discharge pipe 4. In this case, the discharge fluency Q of liquid nitrogen is measured by the flow meter 7, the discharge pressure P is also measured by the pressure gauge on the discharge side, and a performance curve is created.

Since the motor rotation speed is lower than the predetermined rotation speed, the IC performance curve created by this driving test has a performance curve in which the discharge flow ff1Q is smaller than the predetermined flow rate. However, since the motor does not overload, there is no need to reduce the number of pump blades during operation tests, and the boiling point of liquid nitrogen is L.
Since the boiling point is not much different from the boiling point of NG, there is no need to replace pump parts. Therefore, the performance curve of the actual pump can be accurately estimated from the obtained performance curve, and the temperature state of the internal parts of the pump can be tested under conditions close to actual operation.

In addition, in the embodiment of the present invention, a case has been described in which the rotation speed of the pump is reduced by changing the frequency of the motor power supply, but it is also possible to reduce the rotation speed of the pump mechanically. Of course, various modifications may be made without departing from the spirit of the invention.

According to the LNG pump operation test method of the present invention, it is possible to accurately determine the performance curve 0 and the curve during actual operation from the obtained performance curve, so it is possible to easily perform optimal operation of the pump. Therefore, there is no need to replace parts, which improves C1 test efficiency and reduces power consumption.

[Brief explanation of the drawing]

The figure is a detailed explanatory diagram of the present invention. In the figure, 1 is an LNG pump, 2 is a pump pot, 3 is a suction pipe, 4 is a discharge pipe, 5 is a tank, 6 is a flow rate control valve, and 7 is a flow meter.

Claims (1)

[Claims] 1) An operation test method for an LNG pump, which is characterized by using liquid nitrogen as a fluid and performing an operation test by rotating the pump at a rotation speed lower than the rated rotation speed.