6.10 Greasing systems
Various components require greasing in operation to ensure smooth linear or rotational movement between components; oil lubrication is not appropriate. These components include:
- Turbine pedestals/baseplates.
- Steam valve gear pivots.
Previously, attempts were made to provide automatic greasing systems, using a motor-driven multi-piston pump with long pipelines conveying the grease to the various components. Unfortunately, separation and hardening of the grease constituents in the pipelines resulted in frequent blockages and inadequate lubrication.
Modern plant uses bearings consisting of a sintered-bronze matrix, impregnated with PTFE, on a steel backing strip. These bearings are now used under the main pedestals and are provided with manual greasing points. The greasing channels are provided with sufficient area so that the total grease pressure can overcome the deadweight and allow the grease to spread over the bearing surfaces. Grease leakage 'tell tales' are provided so that the effectiveness of the greasing operation can be checked. In order to prevent the ingress of grit and foreign matter, the pedestals are provided with dust shields.
Examples of the greasing points provided on the main steam valve gear pivots are shown on Fig 2.68.