Hydrogenation unit reaction feed interlock!
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The feed interlock for the hydrogenation unit involves closing the reaction feed valve and the interlock cut-off valve. However, to prevent manual errors, a limit setting has been incorporated in the DCS. I would like to know whether, after the interlock is activated, the reaction feed valve closes directly or reaches the set limit
Generally, in DCS function blocks, the interlock level is higher than the limit level; therefore, after an interlock action occurs, the valve will close completely immediately.
Interlock directly cuts off the gas supply, with the valve closing to a safe position. The DCS soft limit does not work
Check whether the interlock feed valve uses an AO output or a DO output; with a DO output, it goes directly to the fault state
It depends on the way the interlock for the feed valve is implemented; generally, there is a solenoid valve in the gas circuit associated with the valve itself, which allows bypassing the valve positioner. Regardless of the valve position set by the DCS, the gas supply is cut off directly, causing the valve to close. If the valve does not come with a solenoid valve and is controlled purely through DCS logic, it depends on what the configuration was at that time; any of those options is possible.