Blue Blush Build Up On Steam Valve Spindles
Blue Blush Build Up On Steam Valve Spindles
(OP)
We have encountered serious Blue Blush build up on valve spindles. Have you found an effective procedure to remove this build up without damaging the base material?





RE: Blue Blush Build Up On Steam Valve Spindles
Some steels, mainly the PH steel develop a pronounced blue blush while others will tend to get blush from oxidation or bluing.
RE: Blue Blush Build Up On Steam Valve Spindles
rmw
RE: Blue Blush Build Up On Steam Valve Spindles
This site had started cycling their turbine unit six years ago. They are now finding a very abnormal amount if build up on the valve spindles and inside the bushings.
RE: Blue Blush Build Up On Steam Valve Spindles
RE: Blue Blush Build Up On Steam Valve Spindles
In the case of the control valves, in a unit that does not cycle much, the valves run open, or mostly open all the time, so they rarely close. Valves in this service build up the "blue" oxide. when the valve is cycled, the oxide is "peeled" off or scraped off by the valve sliding through the seals.
Stop valves and reheat valves have to be exercised perodically to remove this scale, and make sure that if they are called on to activate in a trip, that the oxide build up is not such that the valves would fail to function.
Now that your control valves are being called on to cycle often, the oxide is scraped off, and sometimes to the detirment of the seals or packing or bushings, and then a new layer or coating of oxide builds up, only to be scraped off the next time the valves cycle.
The oxide layer is self protecting. That is to say, that the layer of oxide prevents futher oxidation of the valve spindle. When this layer is scraped off, the base metal is exposed, and a new layer of oxide is formed, only to be scraped off, ad infinitum.
I hope this explaination sheds some light on the situation I believe you described.
rmw