tubing for control valve.

Mr. Kumar must of our drops( if not all) from the instrument air header are 1/2" galvanized pipe,we rarely have a valve right off the header, must of the valves are located within easy access at the valves(I/P's) or any other pneumatic devices.We use 1/2" brass ball valves connected to the pipe and 3/8" tubing to the valves(I/P's) or any other pneumatic devices. Thank you

gate valve is not suitable for control. you need special valve for control. for air seperate block valve may not be required.

I am not using it for control but for blocking. check this figure and then answer.

do we require valve at positioner side or one at he header is enough?

Mr. Kumar , I don't know if a valve at the positioner is "required" when there is a valve at the header.For me as a field instrumentation tech. easy access to the valve is important, if the valve is at the header and it is easy to reach to me that will be sufficient but if way up in the air or hard to reach then it will be wise to install a valve at the positioner or I/P..Thank you sir

In my opinion, if the distance from the header to the valve is large, a ball valve shall be installed near the valve end too for easy access during maintainance.

hello

maily we use one valve at the side of the control valve for blocking not at the header side but if u have one at the header i thinck it will be better to another one at the side of control valve