| Hammering is caused by the relative axial movement of piston and rings as a result of gas loading and inertia when piston changes direction at BDC. Hammering result in enlargement of groove and and may result in ring breakage. Groves are protected by flame hardening or chromium plating. top and bottom on upper groves. or by fitting cast iron inserts. |
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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