hi friends,
anybody tell me about the control valve what is function how is operate what are the accesories .

The purpose of a "Control" valve is to control. It might control flow, level, pressure or tempurature depending on the purpose of loop it is installed in. The valve itself is normally a "globe" type valve body but with an air or electro-phnumatic operator. This operator is controlled through a loop that includes a primary sensor and the control logic.
The normal globe type body control valve will be a single of double port configuration with a sliding "can" type plug with holes or tapered opening to allow fluid or gasses through.

I hope this helps.