We are working on an extension to a small existing DeltaV system. Additional hardware was ordered early this year but delivery on CHARMS at the moment is very long (6-8 months). Although most of the CHARMS have now appeared, we are still short of seven LS DVC HART DTA CHARMS. Has anybody, preferably in the UK, got any spare ones they would be willing to sell or loan??
Assuming we don't manage to source any and they are not delivered, we are looking at a temporary fix to at least allow water trials.This involves using a PAS module which switches 4 mA or 20 mA to the valve via a PAS AO HART CHARM. The PAS module uses a reference to the state of the CSLS trip output that would feed the DVC output CHARM. This seems to work, apart from an issue with HART position feedback.
In existing valves connected to LSDVC CHARMS we use the HART position feedback to confirm the position of the valve. However when the same model of valve is connected to the AO CHARM we get the feedback but it's status is Bad. I can't see why there is anything different in HART communication between the two types of CHARM. Anyone any ideas?