Emergency Shutdown Valve (ESDV) Flanged Connection

https://www.youtube.com/watch?v=0be9IhldkSM

have you ever welded on a gas pipeline? I didn't think so.

Somebody had to weld the companion flanges to the pipe.

Common sense tells me if it has any moving parts, then it should be easily replace in case of failure, with a minimum amount of downtime. After all, "Time is Money"

Flanges on the pipe connection sides are not always necessary for that; valves can often be designed so that all renewable parts are accessible via top and bottom flanges. This can save weight, alignment labor, gasket, and hardware costs.

asked and answered!

ps.. its "THERE" not THEIR

Okay. Thanks everyone for your valuable replies and suggestions. The conclusion is that the standards governing the project will define the type of valve to be used.

...and the forum cannot see them from here.

Agree with prev comments. If governing body doesn't specify, then either works. From the manufacturer point of view, welded connection with removable inner workings since they are usually more economical with less lead time, but some manufacturers like dealing with flanges regardless. The fluid type ESDV's I am used to seeing are either globe or gate type (metal seat) and usually have flanges as they are typically directed by shipbuilding Rules at or on the fuel tanks. Gas type on LNG vessels could be either as they are located outside of the machinery space before the double wall pipe requirement. From an owner/operator perspective, flanges seem to be the often choice for easy/quick replacement.