Multistage centrifugal pump installation technology

The key to the installation technology of the centrifugal pump is how to correctly determine the installation height of the pump (ie the suction stroke). For a typical centrifugal pump, this height refers to the vertical distance from the liquid level to the center line of the pump impeller; for large-flow centrifugal pumps, this height should be considered according to the distance between the high point of the impeller population and the liquid level. It and allowed

The suction vacuum can not be confused. The pump product specification or the nameplate E indicates the allowable vacuum degree refers to the vacuum value on the water pump inlet section, and it is tested under the standard atmospheric pressure, the water temperature of 20 'C, and the rated working condition. And measured. Allowing vacuum to be absorbed does not take into account the flow of water after the suction pipe is fitted

situation. The installation height of the pump is the value of the remaining part that allows the suction vacuum to be deducted from the loss of the suction pipe. It has to overcome the actual terrain water absorption height. The pump installation height cannot exceed the calculated value, otherwise the pump will not be able to pump water. In addition, the magnitude of the influence calculation value is the resistance loss of the suction pipe.

Loss of lift, therefore, it is advisable to use zui short pipe arrangement, and install accessories such as elbows as little as possible, or consider fitting a larger diameter pipe to reduce the flow rate inside the pipe.

It should be noted that when the atmospheric pressure and water temperature at the installation location of the centrifugal pump are different from the test conditions, such as a local elevation of more than 300 m or the water temperature of the pumped water exceeds 20 °C, the calculated value shall be corrected. That is, according to the atmospheric pressure at different altitude elevations and above 2. Saturated steam pressure at °C water temperature

Count. However, when the water temperature is below 20 ° C, the change in saturated vapor pressure is negligible.

From the pipeline installation technology, the suction pipe requires strict sealing, and it cannot leak or leak water. Otherwise, the vacuum at the water inlet of the pump will be destroyed, and the water output of the pump will be reduced. In severe cases, you can't even get water. Therefore, we must conscientiously do the interface work of the pipeline to ensure the construction of the pipeline connection.

quality.

The installation height of the pump can be calculated from the seven vacuum degrees allowed.
If it is known that the pump is allowed to absorb vacuum, the calculated installation height of the pump is calculated according to equation (7-2).
Allow to absorb the vacuum H. Refers to the pressure p at the pump population; the maximum vacuum that can be achieved. The actual allowable suction vacuum height H. The value is not a calculated value. It is the value measured experimentally by the pump manufacturer. This value is attached to the pump sample for the user to check. However, it should be noted that the H given in the pump sample,

The value is to use clean water as the working medium.20. C and the atmospheric pressure are 1.013 × lOs Pa, when the operating conditions and working medium are different, need to be converted. The operating conditions are different from the test conditions and can be converted according to formula (7-1):
Hs'=Hs+(Hs--10.33) - (Hv- 0 .24) (7-1)
Where: Hs' a pump is allowed to absorb vacuum in the field state, m.
The allowable vacuum of Hs in a standard state (or given by the sample), m;
Ha--atmospheric pressure in the field state of the pump, m;
10. 33-atmospheric pressure under standard conditions, m;
Hv——the vaporization pressure of the liquid at the current temperature, m;
0. 24-vaporization pressure of water in standard state, m.
Where: Hg - pump installation height, m;
Hy——liquid level pressure, m;
Ha——standard atmospheric pressure, m;
Mouth s - the average speed of the pumping population, m / s;
Hw - suction pipe hydraulic loss, m.
When the calculated value H: is negative, it indicates that the suction port position of the pump should be below the liquid level of the tank, that is, the backflow.
The installation height of the pump can also be calculated from the NPSH margin. If the necessary NPSH of the pump is known, then calculate the difference of the pump
The height is to be carried out according to equation (7 3):
Hg=( Hy-Hv)-Δh - hw (7-3} where: Hv——liquid saturated vapor pressure.m;
â–³h - the necessary NPSH, m.
When the calculated Hg is negative, it indicates that the suction port of the pump should be below the liquid level of the tank, that is, backfill.

Title Source: Shanghaideng Pump Valve Co., Ltd.