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Reasons For Cylinder Cover Cracking

Cylinder covers are susceptible to cracking due to the high thermal and pressure stresses from combustion. Excess combustion pressures, cylinder temperatures, or over-tensioning during assembly can increase these stresses. To prevent cracking, combustion pressures and cylinder cooling temperatures should be closely monitored, cylinder heads should be tensioned correctly, and cooling water treatment maintained.

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98 views1 page

Reasons For Cylinder Cover Cracking

Cylinder covers are susceptible to cracking due to the high thermal and pressure stresses from combustion. Excess combustion pressures, cylinder temperatures, or over-tensioning during assembly can increase these stresses. To prevent cracking, combustion pressures and cylinder cooling temperatures should be closely monitored, cylinder heads should be tensioned correctly, and cooling water treatment maintained.

Uploaded by

Abebè Teferi
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Reasons for Cylinder Cover Cracking

Cylinder covers are exposed to high levels of working stress resulting from the thermal
and pressure stresses of combustion, which are imposed on the  stress  resulting from
initial head tensioning. These stresses could be increased by:
1. Excess cylinder combustion pressures. This would increase the mechanical
or pressure stress on the head.
2. Excess cylinder thermal stress produced by excess cylinder temperatures, incorrect
cylinder cooling or insufficient cooling water treatment. These would lead to larger
temperature differences across the cylinder head material leading to larger thermal
stresses.
3. Incorrect i.e. over-tensioning of the cylinder cover on assembly. The increase
in initial tension would increase the total stress on the cylinder cover, possibly enough
to produce cracks in the highly stressed areas of the cylinder cover.

How to Prevent Possibility of Cylinder Cover Cracking

The possibility of cracking would be reduced if all of the above causes were eliminated
by correct operation and maintenance of the engine.
1. The cylinder combustion pressure would be monitored by indicator cards or
peak pressure readings. Engine load could also be measured on-line by
exhaust temperatures and turbocharger revolutions, and relating these to the engine
model curves or test bed readings. The engine room staff would be told to monitor
these readings and ensure the maximum levels given were not exceeded.
2. The temperature of the cylinder cooling would be closely monitored to ensure
that the temperatures were not excessive (leading to overheating of the liner), or
too cold (leading to higher temperature gradients across the liner wall, and hence higher
thermal stress). Temperature monitoring would be via control room gauges, and alarm
settings.
3. Initial tensioning of the cylinder head should be carried out to the
recommended hydraulic tension or torque settings. Thus the gauges that are used to
determine these levels must be calibrated regularly.
4. The reserve of cooling water nitrates must be maintained to reduce scaling
or fouling of the cylinder cover heat transfer surfaces, and to maintain the fatigue life of
the covers.

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