Hi All,
apologies for what might be a newbie issue but I have noticed that one of our block valves ( a vent) is going into hold (DC1/SP_D) when placed into CAS on the faceplate.
I have tried downloading the module with DC1/DC_STATE Confirmed Open and DC1/SP_D as OPEN and DC1/FV_D OPEN and but it still goes into HOLD when placed into CAS.
I have noticed that this valves named sets are _VLV_HOLD:CLOSED or OPEN instead of the normal _VLVNO_SP:OPEN
why would HOLD be used here instead of Valve Normally Open named set?
Please help.
thx in advance
Lee
This seems to be an attempt to address the perennial problem of how normally open valves respond during failures. We know that for a vent valve, safety demands we vent when de-energized, however there are other process failure conditions for which we want the vent valve to take a less drastic measure than open. A blanket approach to fail-safing process equipment during a batch hold or emergency stop condition may not be the right approach for a vent valve, for which opening to vent at the wrong time could jeopordize product quality.
Regarding why CAS is impacting the state, have you done a reference check to determine who may be sending a command via the CAS_IN of the block?