We are involves in a natural gas fired power project in the Middle East. Gas is delivered to the plant by a 20 inch pipe that carries gas at 1000psig.

The contractor will install a single emergency shut down valve in the gas line but will not install an upstream isolating valve that will allow maintenance to be carried out on the shut down valve.

Does any one know if it possible/acceptable to install a line blind upstream of the shut down that could be used for maintenance isolation purposes.

Any advice gratefully recieved.

It sounds like you will need to shutdown the source of material upstream to work on the valve/ball valves.  I am sure that there must be a valve somewhere upstream, that could be closed off.  The problem with a line blind is the thickness of what would be required at those pressures.

I have seen some information from a Germany supplier that claims to use a system of cams and levers to move the blind within a pair of bolted flanges which do not appear to restrict the operation of the blind.

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