Can anyone share philosophy of Automatic Block Valve and emergency block valve?
What are considerations in view of piping design.?

Back in the day (before I retired) we used to call these "ESV" (Emergency Shut-Down Valves).
These were normally the standard line class block valve fitted with a rapid action motor or pneumatic operator.
The valve, the operator and the control cables were covered with fireproof insulation.

In an emergency these valves would either close or open (as required) automatically and the plant would be shut-down. 

Automatic block valve can act as your first layer of protection and once the alarm condition is reached (e.g. high level), the valve is shut by means of a software interlock.

The emergency block valve would act as your final layer of protection and the valve should be shut by means of a separate hard-wired interlock.

You can have the same valve performing both applications. e.g. A high level from a level transmitter will shut the valve. If this instrument fails, a separate high high level switch will shut the valve.

I have also seen an application where the above 2 functions are performed by the same valve by having 2 different solenoids each receiving a different signal.

Many plants use gate valves for isolating units at the battery limits etc.  Large gate valves require many turns of the handwheel to open.  Automated valves may use electric actuators to permit remote operation.  An operator may also push buttons to open or close such valves.  Usually a manual hand wheel is also provided as an override when power is lost.  Such a valve would fall into the automated isolation valve description.  Some quarter turn pneumatic valves are also operated using a vane actuator (perhaps gas over oil with stored energy) or double acting pneumatic actuator (perhaps with an air storage cylinder and double check valves on the supply).  Lacking a spring these automated valves would not be suitable as emergency shutdown valves.

A pneumatic actuator on a quarter turn ball or butterfly valve is more common for an emergency shutdown valve.  The emergency shutdown valve should be able to close with no power or air supply.

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