Butterfly Valves as Emergency Shutdown Valves

Ideally full bore valves are used for shutdown line , true, and that is also applicable in Ball valves only . Even i havn't heard of this experiment uptill now .May be because of cost-effectiveness or that much of accuracy is not required .

Check with the Line pressure of that line and PN class of Butterfly valve .

In any of the cases you can ask it in the Pre-bid Meeting , and if the PN class is still worrying you , mention it in Technical Deviation Sheet of the Techno-commercial Bid to the client .

Details of Line ,pressure class, butterfly valve size to calculate the max leakage allowd or the class.

valves are on the Line sizes 20 " and 14", with services like Potable water and process water, Line Design pressure is around 5barg, Temperature 50degC.

Pressure class of the flanges is 150# RF

I think the defining moment here is when you listed potable water, and process water as the fluids being controlled by the emergency shutdown. I would never use a buttefly valve in a steam line or a line transporting hazardous materials, but, in most cases, and probably this one, the emergency shutdown is on other major components such as pumps and mixers, and the water lines won't really constitute a hazard if they leak a bit. Only you know, I hope, and your customer know what these waters are used for. If I am wrong, and they do constitute a hazard, then yes, I agree with you.

By the way, yes, I have seen this done on process skids for water lines under the above listed situation.