Field Bus Communication Failure

  • Thread starter Abdul Rahim Hsino
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Abdul Rahim Hsino

Just completed a new project (gas gathering and compression project in Abu Dhabi, UAE) based on Foundation Field bus (FF). After commissioning, experienced huge no. of Input Open (IOP) alarms, where the communication between DCS and field instruments is interrupted intermittently. We are not loosing control as the interruption is happening for short duration and restored back. It is known as IOP.

This is flooding the Operators Work Station with IOP alarms.
The ICS Vendor is Yokogawa and the FF vendor is PEPPERL + FUCHS (P&F).
Contractor & Vendors tried to resolve the problem without success. P&F proposed to earth the control cables from one end to reduce the noise.
Followed P&F was implemented for one segment. The problem was reduced but not eliminated, even though the noise level is within the acceptable range.

Major O&G companies are now thinking of stop using FF in their new projects. To go back to standard configuration, with HART.

Appreciate any useful comments on the issue.
It sounds like a continuing ground problem to me. Grounding only one end of a cable shield is fundamental. Remember that many FF multiconductor cables have both an overall shield and a shield for each H1 pair. <b>All shields should be grounded only at the power supply end, not in the field.</b> Quality of grounds are critical. It seems to me that there is a ground loop still interfering with the H1 signals. Remember that HART/4-20mA signals are also victims of ground loop noise, probably even more than FF. It seems that the H1 cable shield is carrying AC voltage, which will destroy H1 connectivity.

Dick Caro