Why nimonic coating is provided on exhaust valves ?

In this Article,I have why Nimonic Coating is Provided on exhaust valves of marine diesel engine ?

Why nimonic coating is provided on exhaust valves of Marine Diesel Engine ?

  1. Prevent hot corrosion.
  2. To increase life of the valve.
  3. And to minimize the effect of burning of valve.
Why nimonic coatingbis provided on exhaust valve

Modern Marine diesel Engine working on Heavy fuel Oil ( HFO ) having bore length greater than 300 mm,operates on relatively high exhaust temperature about 350- 400 ℃ .

Under this high temperature ,the uncoated valve stem of the exhaust valve of marine diesel engine may

  • Give up their strength.
  • Leading to reduction to overall life of valve.
  • And cause hot corrosion.

Nimonic coating on valve cause high temperature sanity and it resist hot corrosion.

Now, full coated nimonic valve are available from manufacturer of engine ,which increase life of valve but it will increase the cost marginally.

Note :- Valve seat of the exhaust valve are treated with a harder alloy compound ,stellite.

The coating which is provided on the valve stem of exhaust valves of modern diesel engines is of :-





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