Table of Contents
Exhaust valve leaking is caused by deposits on the valve and seat, corrosion and mechanical damage, while exhaust valve burning is driven by sodium and vanadium compounds in heavy fuel oil attacking the seat at high temperature. Both failure modes are explained below.
Exhaust valve leaking and exhaust valve burning are two related failure modes covered in the main engine guide. This page collects both sections together: the causes of a leaking exhaust valve, and why exhaust valves burn when burning heavy fuel oil.
Exhaust Valve Leaking
- Deposit on valve and valve seat
- Mechanical impact
- Incorrect valve seat material
- Hot corrosion (accelerated oxidation at high temperature) and cold corrosion (sulphuric acid condensation)
- Damage of spring
- Insufficient tappet clearance
- Presence of sodium and vanadium in fuel to a high extent
Cause of exhaust valve burning
When burning of HFO of high viscosity which contains sodium and vanadium, deposits on the valve seat, which at high temperature becomes strongly corrosive, strictly compounds as a result valve will be burned and wear down