Talking about the installation height of the centrifugal pump Hg Calculating the height of the suction allowed vacuum Hs refers to the maximum degree of vacuum that the pressure p1 at the pump inlet allows. The actual allowable suction height, Hs, is not a value calculated according to the equation, but a value determined experimentally by the pump manufacturer, which is attached to the pump sample for user investigation. It should be noted that the Hs value given in the pump sample is the value of the water used as the working medium, the operating conditions of 20 ° C and the pressure of 1.013 × 105Pa when the operating conditions and working medium are not the same, need to be converted. 1 transport water, but the operating conditions and experimental conditions are different, can be converted according to the following formula Hs1 = Hs + Ha-10.33 - Hυ-0.24 2 Conveying other liquids When the liquid is transported and the villain conditions are different from the experimental conditions, the need for two-step conversion : The first step will be based on the above formula Hs1 will be found in the pump sample; The second step is based on the following Hs1 conversion H? S 2 NPSH? H For the oil pump, calculate the installation height using the NPSH , That is, the degree of vacuum that the pump allows to suck the liquid, that is, the allowable installation height of the pump, in meters. Naphthenic residual amount Δh by the pump in the sample, its value is also measured with 20 ℃ water. If you transfer other liquids, also need to be corrected, detailed investigation of the books. Stroke = standard atmospheric pressure (10.33 meters) - NPSH - safe amount (0.5 meters) Standard atmospheric pressure can depress the pipeline vacuum height of 10.33 meters. For example: a pump required NPSH is 4.0 meters, suction Δh? Solution: Δh = 10.33-4.0-0.5 = 5.83 m From the safety point of view, the actual pump installation height should be less than the calculated value. When the calculated value of Hg is negative, it indicates that the suction port of the pump should be below the level of the tank. Example 2-3 A centrifugal pump from the sample was allowed to suction on the vacuum height Hs = 5.7m. It is known that the total resistance of the suction line is 1.5 mH2O and the local atmospheric pressure is 9.81 × 10 4 Pa. The dynamic head of liquid in the suction line is negligible. Test calculation: 1 delivery of 20 ℃ water centrifugal pump installation. 2 instead of conveying 80 ℃ water centrifugal pump installation height. Solution: 1 delivery of 20 ℃ water pump installation height. It is known that: Hs = 5.7m Hf0-1 = 1.5mu12 / 2g≈0 The local atmospheric pressure is 9.81 × 104Pa, basically in line with the experimental conditions of the pump factory, so the installation height of the pump is Hg = 5.7-0-1.5 = 4.2 m. 2 When the delivery of 80 ℃ water pump installation height When the water is delivered at 80 ℃, the Hs value in the pump sample can not be used directly to calculate the installation height. The Hs1 = Hs + Ha-10.33 - Hυ-0.24 Know Ha = 9.81 × 104Pa ≈ 10mH2O, from the appendix to find the saturated vapor pressure of water at 80 ℃ 47.4kPa. Hv = 47.4 × 103 Pa = 4.83 mH2O Hs1 = 5.7 + 10-10.33-4.83 + 0.24 = 0.78m The value of Hs1 is substituted into the equation to obtain the installation height Hg = Hs1-Hf0-1 = 0.78-1.5 = -0.72m Hg is Negative value, indicating that the pump should be installed below the tank surface, at least 0.72m below the surface Single-stage double-suction centrifugal pump Single-stage double-suction centrifugal pump is a new type of energy-efficient water pump with the same energy efficiency, Nearly 20% of the original pump 1. Compact structure Beautiful appearance, good stability, easy to install. 2. Smooth and optimized design of the double suction impeller to reduce the axial force to a minimum, and has excellent hydraulic properties of the leaf, and after precision casting, the pump casing and the surface of the impeller Extreme Brilliance has significant anti-cavitation Performance and high efficiency. 3 bearing selection SKF and NSK bearings to ensure smooth operation, low noise, long service life. 4. Seal selection BURGMANN mechanical seal or packing seal. 8000 hours to ensure operation without leakage. 5. Installation form Assembly without adjustment, according to the site conditions. Discrete or horizontal installation. 6. The installation of self-priming device, can automatically absorb water, that does not need to install the end of the valve, no vacuum pump, no backfill, the pump can start.
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