For a hydraulic pump its inlet port is port is usually large

For a hydraulic pump, its inlet port is port is usually larger in size than the outlet port, while the two ports have the same size in a hydraulic motor. Explain why. To prevent the damage to the pump by fluid comtamination, a filter is often mounted at the end of the suction line. Should a coarse (e.g. 80 mu m) or fine (e. g. 10 mu m) filter be used here? Why?

Solution

1. The piping in the inlet section or inlet port should be much larger as compared to the outlet port as velocity reduces by keeping large inlet diameter. There is only pressure forcing oil at pump inlet that is the atmospheric pressure and if we have a low inlet piping diameter it may lead to high pressure losses which may lead to cavitation and damaging of pump. An overhead reservior is generally used to avoid cavitation but its useful only if the velocity flow is low for which large inlet diameter is necessary.

2. At end of suction line pressure filters are generally installed. These filters act as main filters and generally protect the system from wear. These filters use high grade filtration and have generally a mesh size of 1 to 20 (um) using paper glass fiber and polyester. This filter is generally called safety filter.This filter must handle complete system pressure and must be capable of handling the max flow of the pump. Also, this filter must be fine in order to ensure no large contaminations enter the system through suctioline and cause clogging.