What is the reason for the slow opening of the main valve of steam turbine?

Mill scale produced by the valve stem causes mechanical blockage or the main valve itself is defective.

1, the valve stem will produce mill scale under the working environment of high temperature and high pressure, which will reduce the gap between the valve stem and the valve stem sleeve, increase the friction between them, and cause mechanical jamming.

2. There are manufacturing errors when the main valve leaves the factory, and the design dimensions of inner diameter and outer diameter are different, which leads to the slow opening of the main valve.