What is pump slippage of a gear pump? A gear pump performance data is shown in t
ID: 1843748 • Letter: W
Question
What is pump slippage of a gear pump? A gear pump performance data is shown in the following table for the oil of Specific Gravity 0.9. Barometric pressure = 30.5 inch Hg, Specific weight of mercury = 133 KN/m^3, Specific weight of water = 9.8 KN/m^3, 1 inch = 25.4 mm, 1 psi = 6895 Pa, 1 gpm = 6.309E-5 m^3/s. Calculate pump head in m, fluid power in watts, friction power loss, pump efficiency and net positive suction head if the inner diameter of the pipe is 0.5 inch. Explain the cause of cavitation in a gear pump.Explanation / Answer
A)
when the inlet outlet pressure is more than the inlet pressure of a gear pump, backward flow of oil will takes place this is called slippage in gear pump, and gear pump, slippage is given by the relation= (Qact-Qth)/Qth.
where Qact= Actual discharge of oil
Qth= Theoretical Discharge of oil
C)
Below is a list of possible contributing causes of cavitation:
1. Tank design issues. Turbulence in the tank churns the air into the oil or simply doesn't allow air to be released from the oil. This can be caused by plunging oil returns, low oil level, a tank that is too small, lack of proper baffling, etc.
2. Suction-line leaks. Leaks between the tank and the pump can introduce air. Often this is associated with the shaft seal at the pump that allows air to leak in.
3. Suction-line restriction. Sometimes suction lines are too long, too narrow or simply plugged (e.g., a plugged suction strainer).
4. Insufficient head. Depending on oil viscosity and suction-line conditions, the pump must be located at a sufficiently low elevation to enable oil to flow readily from the tank to the inlet port of the pump.
5. Air-release problems. As oils age and become contaminated, air-release properties become impaired. This simply means that once air bubbles form, they stay locked into the matrix of the oil and don't detrain out of the oil in the reservoir. Moisture contamination and oxidation are known precursors to this problem, among many others.
6. Water vapor. When hot oils become contaminated with water, super-heated steam will form vapor bubbles in the oil.
7. High viscosity. When reservoir temperatures are too cold (during wintertime startup conditions, for example), the viscosity may be too high to enable proper oil flow in the suction line and into the pump. Other causes of high oil viscosity can lead to the same problem.
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