SIL-capable actuators protect BASF plant

30 October 2018

SIL-capable AUMA actuators have been specified as part of a safety system for flue gas scrubbers on a BASF incineration plant in Germany. 

The actuators operate flue gas dampers that protect the GRP scrubbers against excessive temperatures in case of emergency.

To prevent damage to the scrubbing system BASF implemented a protection scheme that, as an overall system, meets the stringent SIL 3 requirements according to IEC 61508. The system includes three flue gas dampers fitted with AUMA electric actuators that are TÜV-certified for use in safety-related systems up to SIL 2/SIL 3 (SIL 3 for redundant system architecture). 

The first flue gas damper is installed upstream of the flue gas scrubber. If inadmissibly high temperatures are detected, the actuator closes the damper to stop flue gas entering the scrubber. The other two actuators open dampers that divert the flue gas to an emergency stack. For maximum safety, these dampers are arranged in series in a two-out-of-two configuration.

The actuators are controlled by a safety PLC that issues a signal to the ESD (emergency shutdown) input of each actuator whenever there is demand for a safety operation. To ensure maximum system availability a UPS provides emergency power for the electric actuators. Each actuator automatically performs a partial valve stroke test (PVST) once a month to ensure that actuators and dampers are working correctly.

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