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We are upgrading our pneumatic air isolation procedures. We have over 200 valves in a plant which are pneumatically driven. The solenoid for these valves are located in the head of the valve. We feed these valves from a mains air header and tap off to each valve with a 6mm supply. Where each valve is connected in to the mains header we have a non-return valve. We now need to be able to isolate the 6mm airline before it feeds into the valve and lock the supply off. The idea to do this would be using a miniature ball valve which is lockable and which also vents off when isolated which releases any air to the valve. Does such an item exists?? I know you can get an inline ball valve which can be 6mm airline in and out but I can't seem to locate any which are lockable.

Thanks

The very first question which comes to my mind is whats the use of NRV? is there any other system connected with the valves like air cylinders for forcing close/open of the valve in case of air failure. If yes then you are kindly advised to restore that system also. If no such system is there there remove these NRV as these NRV's serves no purpose.

Secondly installing 6 mm ball valves is standard procedure but why you need a venting arrangement for that? For the C/V's u must have used the regulators which you can use for drain purpose and for SDV's simply power off the solenoid valves. This will serve the purpose of drain.

Hope this clarifies your doubt. But my advice once again is to check the utility of NRV's.