JPH01273898A - Performance surveillance/diagnosticment method for low temperature liquefied gas pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for monitoring and diagnosing the performance of a pump that conveys low-temperature liquefied gas such as ING stored in a low-temperature tank.

[Prior Art] Centrifugal pumps are used to transport low-temperature liquefied gases such as LNG and LPG stored in low-temperature tanks.

[Problems to be Solved by the Invention] By the way, the liquid level in the low-temperature tank changes all the time, which causes the pressure on the suction side of the pump to change, and when that pressure decreases, cavitation occurs in the pump, causing cavitation due to generated gas. There is a problem in that the ability of the impeller to generate centrifugal force decreases due to crowding, etc., and the pump's performance decreases. When operating at a liquid level higher than
When receiving G, cavitation is likely to occur in the pump because the liquid level is lowered as much as possible. However, unless the limit of the pump pressure drop due to cavitation is accurately determined, it will not be possible to operate the pump with the liquid level lowered to the limit.

The present invention has been made in consideration of the above-mentioned problems, and is capable of monitoring the degree of occurrence of cavitation in a pump.
An object of the present invention is to provide a performance monitoring and diagnosis method for a pump for low-temperature liquefied scum that can diagnose whether the resulting performance degradation is within a range that does not impede operation.

[Means for Solving the Problem] In order to achieve the above object, the present invention detects the meteor and pressure of the low-temperature liquefied gas from the pump when transporting the low-temperature liquefied gas in the low-temperature tank with a pump. The vibration acceleration of the pump is detected and the degree of cavitation is diagnosed from these detected values.

[Function] According to the above configuration, by first detecting the flow rate and pressure from the pump, it is possible to determine the decrease in capacity with respect to the standard curve of flow rate and pressure (head) of the pump, and this is combined with the vibration acceleration of the pump. This allows us to determine the degree of cavitation occurrence and determine whether it is okay to continue operating the pump.

[Example] Hereinafter, preferred embodiments of the present invention will be described based on the accompanying drawings.

In Figure 1, 1 is a low temperature tank, inside which LNG,
Low-temperature liquefied gas L such as LPG is stored.

A centrifugal pump 3 is connected to this low-temperature tank 1 via a suction pipe 2, and a pipe 4 is connected to the discharge side of the pump 3, so that the pump 3 is supplied to a liquefied gas utilization device (not shown), etc. .

A flow meter 5 and a pressure gauge 6 are connected to this pipe 4, and each is connected to a diagnostic system 9 via an online connection 7.8. Further, an acceleration sensor 10 for detecting vibration acceleration of the pump 3 is housed in the pump 3, and the detected value is connected to the diagnostic system 9 via an online connection 11.

Note that 12 is a check valve connected to the pipe 4, and 13 is an on-off valve.

In the above, first, if the suction side pressure of the pump 3 is constant, the flow i#Q and the head H of the liquefied gas pump have the relationship shown by the reference head curve Q in FIG. 2. Furthermore, when the suction side pressure decreases, the performance decreases as shown by the dotted curve rn.

Therefore, first, the data of the reference head curve J of the pump 3 when the liquid level of the liquefied gas L in the low-temperature tank 1 is at its highest is input into the diagnostic system 9, and at the same time, the data of the reference head curve J of the pump 3 when the liquid level of the liquefied gas L in the low temperature tank 1 is at its highest is input, and at the same time, the data of the reference head curve J of the pump 3 is inputted into the diagnostic system 9. Flow JiQo, point ao of head (pressure) Ha
Enter.

While the pump 3 is in operation, the flow rate value detected by the flow meter 5 and the pressure (head) value detected by the pressure gauge 6 are input to the diagnostic system 9 via the online system 7.8.

Now, suppose that this flow rate and pressure (lifting head) are operating at a meteor (J+, lifting head H+) as shown at point a1 in Figure 2,
It can be seen that the flow rate and head of this point a1 are lower than the initial point aO, and the performance is degraded, but it cannot be determined whether the decrease due to the occurrence of cavitation in the pump 3 is due to a decrease in the liquid level9. , the vibration of the pump 3 is detected by the acceleration sensor 10 and the vibration of the pump 3 is detected by the acceleration sensor 10.
, by inputting it into the diagnostic system 9 online 11, it is possible to judge whether the performance has deteriorated due to cavitation.

That is, as the incidence of cavitation increases, the vibration of the pump 3 increases, and the degree of cavitation can be diagnosed based on the increase in vibration.

Therefore, the flow rate Q1 inputted in the diagnostic system 9 and the head H
1 to the initial stage (compared with ifQo and Ha, and from the detected value of vibration acceleration input at the same time, it is determined that the performance deterioration of the pump 3 is due to the decrease in suction side pressure, or the performance deterioration also includes cavitation at the same time. It can be appropriately determined whether

When the degree of cavitation occurrence reaches a dangerous range, this diagnostic system displays it on the CRT and stops the operation of the pump 3.

[Effects of the Invention] As is clear from the above explanation, the present invention exhibits the following excellent effects. By detecting acceleration, it is possible to monitor and diagnose deterioration in pump performance due to cavitation.

C2'] Since it can be operated close to the limit of cavitation generation, low-temperature liquefied gas can be delivered m to the dead stock of the low-temperature tank.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing the performance of the pump in the present invention. In the figure, 1 is a low temperature tank, 3 is a pump, 4 is piping, 5 is a flow meter, 6 is a pressure gauge, 9 is a diagnostic system, and 10 is an acceleration sensor. Patent applicant: Ishikawajima-Harima Heavy Industries Co., Ltd. Representative patent attorney: Nobuo Kinutani 4... Jinsuga 9... Diagram 2

Claims (1)

[Claims] 1. When transporting low-temperature liquefied gas in a low-temperature tank with a pump, detect the flow rate and pressure of the low-temperature liquefied gas from the pump, as well as detect the vibration acceleration of the pump, and diagnose the degree of cavitation from these detected values. A method for monitoring and diagnosing the performance of a pump for low-temperature liquefied gas.