Class 2 (2nd Engineer) MEKM 📅 Apr 2018

Exam Question

With reference to piston rings:

(a) State reasons for breakage.

(b) How maintenance and engine operation could minimize breakage?

(c) Explain the possible consequences with respect to performance and safety of operating the engine with broken or severely worn piston rings

Reference Answer

(a) Reason for piston ring breakage:
Excessive wear in the cylinder liner leads to increased piston ring movement, both radially and axially. This fluctuating motion can cause tilting and eventual breakage of the rings.
If the piston ring does not exert sufficient pressure on the liner, gas pressure can penetrate between the ring and liner, collapsing the ring into the groove and causing breakage.
Ridge formation near scavenge pockets can create stress concentrations at the piston ring's radial edge, promoting fracture.

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