| Axial clearance or vertical clearance is measured by inserting a feeler gauge between the ring and groove. The top two compression rings will have greater values than the others owning to high temperature expansion. But it wont exceed .2mm. For lower compression ring maximum will be .125 mm. for oil scrapper rings- .0625mm. Butt clearance or ring gap can be measured by putting the ring in a new liner or the lower part of the old liner. it should be 4% cylinder bore. |
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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