JPS608494A - Pulse measuring method of pump lift - Google Patents

Abstract

PURPOSE:To measure the pump lift accurately by providing a liquid tanks having no pressure variation in front and rear of a pump while employing a piping system which will never resonance with the vibration of pump where said pump and liquid tank are coupled through suction and delivery pipes of specific dimension. CONSTITUTION:Liquid tanks 2, 2 having no pressure variation for maintaining constant water level are provided in front and rear of a pump 1. The length of suction and delivery pipes 3, 4 coupling between the pump 1 and liquid tank 2 is made shorter than (30c)/(anz) when assuming the sound speed is cm/sec, rotation of pump 1 is m rpm, number of vanes is z and the number of casing volute of pump 1 is (a). Consequently, the length of pipings 3, 4 is made shorter than 1/2 of the vibration wavelength of the pump 1 to prevent resonance. When measuring the pulsation of pump lift by means of pressure converters provided at the suction and delivery of the pump 1 with such structure, accurate value not subjected to the influence of piping system can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring pump lift pulsation that allows accurate measurement by using a piping system.

A conventional method for measuring pump head pulsation will be explained with reference to FIGS. 1 and 2. Figure 1 shows three types of pump A.

For B and C, the maximum pulsation amplitude of the pump head H relative to the pump rotation speed n when the underground water tank and the pump suction and discharge ports are connected with pipes of a certain length and operated in the conventional manner. It is a graph showing changes in ΔHmax. In order to confirm the cause of this pulsation, since the pump head H is proportional to the square of the pump rotation speed n, the maximum pulsation amplitude △Hmax was divided by the square of the rotation speed B to make it dimensionless. A graph of /n2 is shown in FIG. The value that appears here that is not proportional to the square of the pump rotation speed n indicates the presence of pulsation that occurs regardless of the pump rotation speed n, that is, the pulsation that occurs when the piping resonates with the vibration of the pump. It can be seen that if this is done without paying attention to the piping system, the pulsation of the pump head H will not necessarily be accurately measured.

In order to solve the problem described in 1F, the present invention provides a liquid tank with zero pressure fluctuation before and after the pump, and reduces the sound velocity to Crn/8 e.
G + When the rotational speed of the pump is nrpm, the number of blades of the pump is 2, and the volume of the pump casing is 8, the length of the suction pipe and discharge pipe is less than -m, and the 111 pump and liquid tank are connected. The present invention provides a pump head pulsation measurement method that is characterized by successively performing the following: (1) Boundary conditions in which the influence of pressure fluctuations beyond the liquid tank are removed in the liquid tank and the pressure fluctuations become zero is given to the pump (2) The length of the suction pipe and the discharge pipe are each less than 7 of the vibration wavelength of the pump = -m, and the vibration frequency of the pump is a
Since resonance with nzI(z does not occur), accurate pulsation measurement of the pump head can be performed.

An embodiment of a pump lift pulsation measuring method to which the present invention is applied will be described with reference to FIG. Figure 3 is a layout diagram of the pump head pulsation measuring device that applies the Kihatsu Kamei. In Figure 1, 1 is the pump, 2 is the liquid tank, 3 is the suction pipe, 4 is the discharge pipe, and 5 is the pressure converter. Show the container.

A liquid tank 2 is provided before and after a pump 1 to keep the water level constant at all times. - If an airtight liquid tank with air sealed in the F section is used, the volume can be reduced. child.

This eliminates the influence of pressure fluctuations beyond the liquid tank, and provides the pump 1 with a boundary condition in which the pressure fluctuations are zero.

In addition, a suction pipe 3 and a discharge pipe 4 connect the pump 1 and the liquid tank 2.
The length of is, the speed of sound is am/sec, the rotation speed of pump 1 is n rpm, pump! The number of blades is 2. When the number of casing volutes of the pump 1 is 8, each is less than □m. As a result, the piping becomes less than m of the vibration wavelength of the pump, and resonance with the vibration frequency of the pump does not occur.

By configuring the measuring device in this way and measuring the pulsation of the pump lift using the pressure transducers 5 provided on the suction side and the discharge side of the pump 1, accurate values can be obtained that exclude the influence of the piping system.

[Brief explanation of drawings]

Figure 1 is a graph of the maximum pulsation amplitude obtained by the conventional pump head pulsation measuring method, Figure 2 is a graph of the value obtained by dividing it by the square of the pump rotation speed n, and FIG. 3 is a layout diagram of a pump head pulsation measuring device to which the present invention is applied. ■...Pump, 2...Liquid tank, 3...Suction pipe, 4...
・・Discharge pipe

Claims (1)

[Claims] A liquid tank with zero pressure fluctuation is provided before and after the pump. The speed of sound is Om/860 + the rotation speed of the pump is nrpm, and the number of blades of the pump is 2. A method for measuring the pulsation of a pump head, characterized in that the measurement is carried out by connecting a pump and a liquid tank with a suction pipe and a discharge pipe whose lengths are less than -m, where the number of pump casings is a.