Troubleshooting

Today I investigated a CT fan motor current feedback issue in an Emerson Ovation DCS where the analog input showed BAD VALUE with frozen low current indication. Initial checks suggested either: AI channel failure Current transducer issue Open 4–20 mA loop Field ammeter indicated normal motor current, which confirmed the actual process was healthy. After tracing the signal path and comparing with a healthy loop, a loose cable termination inside the switchgear was identified. Replacing the cable lugs and tightening the terminals restored a stable 15 mA signal and normal DCS indication. ...

As per CCR information, I checked historical data and logics of gland steam supply system valves and found out that the valves are working as per control signal, however the fluctuation of pressure arises from somewhere else, the control valve operation is not the cause of the fluctuation, rather it operate in accordance of the pressure, hence it is the effect.