Abstract
The paper describes how, by programmed reduction of steam pressures and temperatures, the saturation point in the blade system of a steam turbine may be moved towards the inlet end, thus progressively washing off soluble blade deposits.
The condition of steam wetness, produced in the blades, results from the heat drop and it is pointed out that having the machine on load is an essential part of the process. The effects of pressure and temperature variations on turbine expansion and vibrations are also considered.
The effect of varying pressure on the boiler brings to light the important fact that this is the more sensitive element in the unit and the drum conditions will limit the process rate.
The result of washing is to present the turbine and boiler in the optimum condition for maintenance. The saving in cooling time is considerable, barring time on a 60 MW turbine is reduced by 50 h and the boiler may be cooled and emptied of water overnight.
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