Hey Guys,
I am new in this forum,

for controlling level of the storage tank of deaerator we used overflow valve in drain line, can we use steam trap too? steam will not goto drain with water?

Tanx in advance.

Do you mean heater drain system? Deaerator normally blows down to atmospheric tank. The line doesnt need a steam trap.
Also the same for overflow line. Deaerator has a level control system. This is a critical control point or trip level control point. I am not sure if overflow line is required. If it is a coal plant there shall be a heater drain system which will relieve the water to cascading drain system.

Cheers

No, you can't use a steam trap in the deaerator over flow line,as it won't solve the purpose. Vapor from the deaerator has to be revomed after deaeration has taken place and for that top vent is given. Overflow drain line should have a valve which opens as level goes upto a certain level.