Q: For the STA 4-Wire SIL 2 and SIL 3 Compliant Programmable Current/Voltage and RTD/Thermocouple Safety Trip Alarms, can the process alarm relays be configured as Failsafe? Can the process relay output of the SPA2-TRPRG be configured Failsafe?
A: The output relays of the STA are configured only as Failsafe. For example, the coils are de-energized in the alarm condition or when there is a loss in power. For systematic integrity up to SIL 3 and for random integrity up to SIL 2, the STA is also exida certified 61508:2010. This means that an STA is approved for single use in Safety Instrumented Systems (SIS) up to SIL 2 and in redundant architectures (1oo2, 2oo3, etc.) up to SIL 3.
The output relays of other alarms that we offer such as the SPA2 can be configured either as Failsafe or Non-Failsafe.