Explain latest developments in
Marine ‘Tribology’.
Tribology is the
science and engineering of interacting surfaces in relative motion. It
includes the study and application of the principles of
· friction
· lubrication
· wear
The tribological interactions of a solid
surface's exposed face with interfacing materials and environment may result in
loss of material from the surface. The process leading to loss of material is
known as "wear". Major types of wear include abrasion, friction
(adhesion and cohesion), erosion, and corrosion.
Wear can be minimised by modifying the surface
properties of solids by one or more of "surface engineering"
processes (also called surface finishing) or by use of
lubricants (for frictional or adhesive wear)
There are world’s two biggest manufacturers of large marine diesel
engines, MAN B&W and Wartsila .
Sulzer RTA-series
engines now incorporate TriboPack technology -a package of design measures
that enable the TBO of the cylinder components, including piston ring renewal,
to be extended to at least three years. At the same time, TriboPack allows the
further reduction of cylinder lubricating oil feed rate.
The design measures
incorporated in TriboPack are:
1. Multi-level cylinder lubrication
2. Liner of the appropriate material, with sufficient hard phase
3. Careful turning of the liner running surface and deep-honing of the liner over the full length of the running surface
4. Mid-stroke liner insulation, and where necessary, insulating tubes in the cooling bores in the upper part of the liner
5. Pre-profiled piston rings in all piston grooves
6. Chromium-ceramic coating on top piston ring
7. RC (Running-in Coating) piston rings in all lower piston grooves
8. Anti-Polishing Ring (APR) at the top of the cylinder liner
9. Increased thickness of chromium layer in the piston-ring grooves.
2. Liner of the appropriate material, with sufficient hard phase
3. Careful turning of the liner running surface and deep-honing of the liner over the full length of the running surface
4. Mid-stroke liner insulation, and where necessary, insulating tubes in the cooling bores in the upper part of the liner
5. Pre-profiled piston rings in all piston grooves
6. Chromium-ceramic coating on top piston ring
7. RC (Running-in Coating) piston rings in all lower piston grooves
8. Anti-Polishing Ring (APR) at the top of the cylinder liner
9. Increased thickness of chromium layer in the piston-ring grooves.
A key element of
TriboPack is the deep-honed liner. Careful machining and deep honing gives the
liner an ideal running surface for the piston rings, together with an optimum surface microstructure.
The Anti-Polishing
Ring prevents the build up of deposits on the top land of the piston which can
damage the oil film on the liner and cause bore polishing.
It is also important
that the liner wall temperature is adapted to keep the liner surface above the
dew point temperature throughout the piston stroke to avoid cold corrosion.
Mid-stroke insulation and, where necessary, insulating tubes are therefore
employed to optimize liner temperatures over the piston stroke.
Other development
Alpha lubrication (MAN)
- Electronically controlled cylinder lubrication.
- The lube oil is injected exactly when the piston ring pack is passing the lube oil quills, thus ensuring the best possible utilisation of the costly lube oil.
Anti polishing ring.
Piston ring :-CPR, Gas tight lock and controlled leakage grooves.
New tie rod design (MAN)
Development in Bearing design
- Increase in bearing area
- Shape changed( lemon shaped)MAN
- Bearing temperature monitoring for moving bearing
- On line bearing wear measurement.
- Thick shell-Flex edge design(MAN)
- Thin shell-Blend edge design
