Centrifugal pump installation requirements and precautions

Centrifugal pump installation requirements and precautions

Centrifugal pumps are available in vertical, horizontal, single-stage, multi-stage, single-suction, double-suction, self-priming and other forms. The centrifugal pump works by rotating the impeller to cause the water to move in a centrifugal motion. Before the pump is started, the pump casing and the suction pipe must be filled with water, and then the motor is started, so that the pump shaft drives the impeller and water to perform high-speed rotation movement, the water is centrifugally moved, and is raked to the outer edge of the impeller, and flows through the volute pump casing. The road flows into the water pressure line of the pump. Then we will briefly describe what needs to be paid attention to when installing a centrifugal pump.

First, the centrifugal pump installation precautions key installation technology

The key to the installation technology of the pipeline centrifugal pump is to determine the installation height of the centrifugal pump, that is, the suction stroke. This height refers to the vertical distance from the water source to the centerline of the centrifugal pump impeller. It is not to be confused with the allowable vacuum height. The allowable vacuum height indicated on the pump product specification or on the nameplate refers to the vacuum value on the pump inlet section. Further, it was measured by a test under the conditions of 1 standard atmospheric pressure and a water temperature of 20 °C. It does not take into account the flow of water after the suction pipe is fitted. The installation height of the pump should be the value of the remaining part that allows the suction vacuum height to be deducted from the loss of the suction pipe. It must overcome the actual terrain water absorption height. The installation height of the pump should not exceed the calculated value, otherwise the centrifugal pump will not be able to pump water. In addition, the magnitude of the influence calculation value is the resistance loss head of the suction pipe. Therefore, it is advisable to use the short piping arrangement of the Zui, and to install accessories such as elbows as little as possible. It is also conceivable to properly fit the water pipes with a larger diameter to reduce the flow velocity inside the pipe.

It should be pointed out that when the elevation and water temperature of the installation place of the pipeline centrifugal pump are different from the test conditions, such as the local altitude above 300 meters or the water temperature of the pumped water exceeds 20 °C, the calculated value should be corrected. That is, the atmospheric pressure at different elevations and the saturated vapor pressure above 20 °C. However, when the water temperature is below 20 ° C, the saturated steam 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 centrifugal pump will be destroyed, so that the water output of the centrifugal pump will be reduced, and even if it is serious, the water will not be pumped. Therefore, it is necessary to carefully do the interface work of the pipeline to ensure the construction quality of the pipeline connection.

Second, the installation height Hg calculation

Allowing the suction vacuum height Hs means that the pressure p1 at the pump inlet can be allowed to reach a large degree of vacuum, and the actual allowable vacuum height Hs value is not a value calculated according to the formula, but a value determined experimentally by the pump manufacturer. This value is attached to the pump sample for user review. It should be noted that the Hs value given in the pump sample is the value when the water is used as the working medium, the operating conditions are 20 ° C and the pressure is 1.013 × 105 Pa. When the operating conditions and working medium are different, the conversion is required.

1. Conveying clean water, but the operating conditions are different from the experimental conditions, and can be converted according to the following formula: Hs1=Hs+Ha-10.33 - HÏ…-0.24 2 Transporting other liquids When the conditions of the liquid to be transported and the villain are different from the experimental conditions, Two-step conversion: * step according to the above formula will be Hs1 detected in the pump sample; the second step will convert Hs1 to H?s according to the following formula

2, NPSH Δh For the pump model, calculate the installation height with the NPSH Δh to calculate, that is, the vacuum that the pump allows to absorb liquid, that is, the allowable installation height of the pump, in meters. The NPSH Δh was taken from the oil pump sample and its value was also measured with 20 ° C water. If other liquids are transported, corrections are also required. Check the relevant books.

Suction stroke = standard atmospheric pressure (10.33 m) - NPSH - safety (0.5 m) The standard atmospheric pressure energy pipeline vacuum height is 10.33 m. For example: a pump must have a NPSH of 4.0 meters, and ask for a suction Δh? Solution: Δh=10.33-4.0-0.5=5.83 m

From a safety point of view, the actual installation height of the pump should be less than the calculated value. When the calculated Hg is negative, the pump's suction port position should be below the tank level. Example 2-3 A centrifugal pump was found to allow the vacuum height Hs = 5.7 m from the sample. It is known that the total resistance of the suction line is 1.5 mH2O, the local atmospheric pressure is 9.81 x 104 Pa, and the dynamic head of the liquid in the suction line is negligible. Trial calculation: 1 Install the centrifugal pump when transporting 20°C clean water. 2 Change the installation height of the centrifugal pump when transporting water at 80 °C. Solution: 1 The installation height of the pump when delivering 20°C clean water. It is known that: Hs=5.7m Hf0-1=1.5m u12/2g≈0 The local atmospheric pressure is 9.81×104Pa, which is basically consistent with the experimental conditions when the pump leaves the factory, so the installation height of the pump is Hg=5.7-0-1.5=4.2 m. 2 When transporting 80°C water when transporting 80°C water, the installation height cannot be calculated directly by using the Hs value in the pump sample. It should be converted to Hs according to the following formula, ie Hs1=Hs+Ha-10.33 - Hυ- 0.24 It is known that Ha = 9.81 × 104 Pa ≈ 10 mH 2 O, and the saturated vapor pressure of water at 80 ° C is found to be 47.4 kPa by the appendix. Hv=47.4×103 Pa=4.83 mH2O Hs1=5.7+10-10.33-4.83+0.24=0.78m The Hs1 value is substituted into the formula to find the installation height Hg=Hs1-Hf0-1=0.78-1.5=-0.72m Hg A negative value indicates that the pump should be installed below the pool level, at least 0.72m below the liquid level.

Single stage double suction centrifugal pump

The single-stage double-suction centrifugal pump is a new type of high-efficiency and energy-saving water pump. Under the same energy conditions, its operating efficiency can be nearly 20% higher than that of the original water pump.

1. Compact structure, good stability and easy installation.

2. The double suction impeller with stable and optimized design reduces the axial force to the low limit of Zui, and has excellent hydraulic performance. It is precision cast, and the inner surface of the pump casing and the surface of the impeller are extremely brilliance with significant anti-cavitation. Performance and efficiency.

3. The bearings are made of SKF and NSK bearings to ensure stable operation, low noise and long service life.

4. The shaft seal is BURGMANN mechanical seal or packing seal. Can guarantee 8000 hours of operation without leakage.

5. The installation form does not need to be adjusted during assembly, depending on the conditions of use on site. Discrete or horizontal installation.

6. Add self-priming device, such as self-priming pump product, to achieve automatic water absorption, that is, no need to install the bottom valve, no vacuum pump, no need to backfill, the pump can start.

Third, centrifugal pump installation precautions

The basic installation of the centrifugal pump should pay attention to the following issues:

(1) The surface of the mounted base must be flat, clean and able to withstand the corresponding loads.

(2) Use anchor bolts where they need to be fixed.

(3) For vertically installed pumps, the anchor bolts must have sufficient strength.

(4) If installed vertically, the motor must be above the water pump.

(5) When fixing on the wall, pay attention to alignment and alignment.