Upgrading RLB engines

Based on field tests carried out between 1991 and 1995, a retrofit package of modifications was introduced for Sulzer RLB90 engines in 1993 and for RLB66 engines in 1995. The main element is the change to loop-cooling in the cylinder liners, an improved cooling technique that reduces the thermal and mechanical stresses in the top collar of the liner (Figure 12.46). By optimizing the running surface temperature, the system also reduces corrosive wear and extends the time-between-overhauls up to two years.

The retrofit package comprises the loop-cooled cylinder liners as well as:

• A new fully gas-tight, vermicular top piston ring of increased thickness.

• A modified top piston ring groove with increased height and increased thickness of chromium layer.

• Multi-level lubrication.

• A new water guide jacket to suit the new liner.

• A modified condensed water drain from the scavenge air receiver.

As RLB engines exploit loop scavenging with both scavenge and exhaust ports in the lower part of the liner, the fully gas-tight top ring significantly reduces the lateral forces at the piston skirt in addition to reducing the blow-by of hot combustion gases—both of which increase the piston skirt life. The package can be applied to the engine either as a full package or step-by-step (intermediate package) depending on service experience with the liners and whether the general piston-running behaviour meets today's expectations. It is also possible to replace individual original liners with loop-cooled units whenever they need to be renewed; there is no problem in running loop-cooled and original design liners together in the same engine.

See Chapter 9 for details ofSulzer research engines, and see Introduction for Sulzer's early low speed engine designs.

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