4.4   Turbine by-pass systems


This comprises a pipework system with valves and pressure dropping devices to enable live steam from the steam raising plant to by-pass the turbine completely and be dumped into the condenser.

The associated control system will open the by-pass according to the specific needs of the plant. The need for a by-pass system and the purposes to which it may be put are discussed in this section. The details of its physical implementation are discussed in Chapter 2.

The requirement for, and configuration of, by-pass systems are mainly governed by the boiler arrangement. The general considerations applicable to fossil-fired and AGR superheat cycles are discussed first. The special considerations for PWR wet steam plant, using steam reheat, follow.

      4.4.1   Superheat plant

      4.4.2   By-pass capacity

      4.4.3   System effects

      4.4.4   Improvement of start-up capability

      4.4.5   PWR wet steam plant

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