High Head Vertical Inline Pipeline Pump For Municipal Water Supply & Drainage

The High Head Vertical Inline Pipeline Pump for Municipal Water Supply & Drainage core of the installation technology for centrifugal pumps in pipelines lies in accurately determining the installation height (i.e., suction head) of the pump. This height refers to the vertical distance from the water surface of the source to the centerline of the pump's impeller. It is important to note that it should be distinguished from the concept of "allowable suction lift". The allowable suction lift indicated in the pump's manual or label is the vacuum value at the water inlet section measured under standard atmospheric pressure and water temperature of 20°C, and does not take into account the influence of water flow resistance after the actual suction pipe configuration.
The actual installation height should be the allowable suction lift minus the head loss of the suction pipe. The remaining part can then be used to overcome the actual terrain suction height. If the installation height exceeds the calculated value, it will cause the pump to fail to draw water normally.
High Head Vertical Inline Pipeline Pump for Municipal Water Supply & Drainage The head loss of the suction pipe directly affects the determination of the installation height. To reduce this loss, it is recommended to reasonably shorten the pipe length, reduce the number of bends and other accessories, or appropriately increase the pipe diameter to reduce the flow velocity.
It should be noted that if the installation location is above 300 meters in altitude or the water being pumped has a temperature higher than 20°C, the calculated value should be corrected. Mainly consider the local atmospheric pressure and the saturated vapor pressure at the corresponding water temperature. When the water temperature is lower than 20°C, the influence of saturated vapor pressure can be ignored.
In terms of pipeline installation, the suction pipe must ensure strict sealing to prevent air leakage or water leakage, otherwise it will reduce the pump's inlet vacuum degree, resulting in a decrease in water output or even inability to draw water. Therefore, the construction quality of pipeline interface connections must be strictly controlled to ensure reliable connection.

High Head Vertical Inline Pipeline Pump for Municipal Water Supply & Drainage

1. Calculation of the installation height Hg for centrifugal pumps
Allowing for the maximum vacuum height Hs at the pump inlet means the maximum vacuum level that can be achieved at the pump's inlet. In practical applications, the Hs value is not calculated using a formula but is determined by the manufacturer through a water test (under conditions of 20°C and a pressure of 1.013×10⁵ Pa). If the operating conditions or the medium change, the Hs value provided by the sample needs to be converted accordingly.
(1) When pumping clean water but with different operating conditions from the test conditions, it can be converted using the following formula:
Hs1 = Hs + (Ha - 10.33) - (Hυ - 0.24)
(2) When pumping other liquids, when the conditions of the liquid being pumped and the reverse flow are different from the test conditions, two-step conversion is required:
The first step is to obtain Hs1 using the above formula from the pump sample; the second step is to convert Hs1 into Hs using the following formula:
The head loss = standard atmospheric pressure (10.33 meters) - head loss due to cavitation - safety margin (0.5 meters)
Standard atmospheric pressure can press the liquid to a vacuum height of 10.33 meters.
For example: If the required cavitation margin for a certain pump is 4.0 meters, what is the suction height Δh?
Solution: Δh = 10.33 - 4.0 - 0.5 = 5.83 meters
From a safety perspective, the actual installation height of the pump should be less than the calculated value.
When the calculated Hg is negative, it indicates that the suction inlet position of the pump should be below the liquid level of the tank. For example, a centrifugal pump from the sample was found to have a permitted suction vacuum height Hs = 5.7 meters. It is known that the total resistance of the suction pipeline is 1.5 meters of water column, and the local atmospheric pressure is 9.81×10⁴ Pa. The dynamic head of the liquid in the suction pipeline can be ignored.
Calculate:
(1) Installation of the pump when pumping 20°C clean water;
(2) Installation height of the pump when pumping water at 80°C.
Solution:
(1) Installation of the pump when pumping 20°C clean water
Given: Hs = 5.7 meters
Hf0 - 1 = 1.5 meters u12/2g≈0
The local atmospheric pressure is 9.81×104 Pa, which is basically consistent with the experimental conditions at the time of the pump's manufacture. Therefore, the installation height of the pump is Hg = 5.7 - 0 - 1.5 = 4.2 m.
(2) Installation height when pumping 80°C water
When pumping 80°C water, the Hs value in the pump sample cannot be directly used to calculate the installation height. It is necessary to convert Hs according to the following formula:
Hs1 = Hs + (Ha - 10.33) - (Hυ - 0.24)
Where Ha = 9.81×104 Pa ≈ 10 mH2O. From the appendix, the saturated vapor pressure of 80°C water is found to be 47.4 kPa.
Hv = 47.4×103 Pa = 4.83 mH2O
Hs1 = 5.7 + 10 - 10.33 - 4.83 + 0.24 = 0.78 m
Substitute the Hs1 value into the formula to obtain the installation height
Hg = Hs1 - Hf0 - 1 = 0.78 - 1.5 = -0.72 m
The negative value of Hg indicates that the pump should be installed below the water level of the tank, at least 0.72 m lower than the water level.