Drop in pressure in suction side is greater than vapour pressure of liquid, possibility of liquid drawing vapour is there and vapour cavities are formed which moves to high pressure regions and collapses creating shock waves, which may result in errosion of parts.
Since very small needle lift is obtained in the test equipment result in an unequal pressure distribution in the cut off shaft resulting in a hard contact in a small area along with high frequency oscillations, low lubricity of test oil will increase the chance of seizure. Full lift and high lubricity of heavy oil eliminates this risk of seizure during normal operation.( Always open and clean slide type valves before testing as cold sticky heavy oil along with small clearances can cause restriction in the movement of the spindle).
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