2.4 Steam strainers
In order to prevent solid particles of foreign matter from being carried into the turbine by the incoming steam and causing damage to the blading, each stop valve is surrounded by a cylindrical strainer which has many small diameter holes, ranging from 5-2 mm depending on the manufacturer.
Even particles of this size can cause serious blading damage, it is therefore essential that a thorough steam blow of all pipework is carried out before a set is commissioned. The risk of damage to new plant from debris, pieces of weld metal, etc., which may be swept through the pipe, used to be minimised by fitting extra-fine commissioning strainers in place of the final strainers. However, because of the time associated with strainer removal, modern practice is to rely on the final strainers to trap all debris.