There are many applications where the process alarm trip is critical. In these cases, if the process equipment is not brought to a safe condition it can cause expensive maintenance, production loss, or environmental impact. The commercial impact is enough that the cost of a second or redundant trip source is negligible.
Reasons for redundant alarm trips:
- Loss of flow requires that a pump be shut down to protect it
- If final pH correction is out of specification, you need to divert the effluent
- High vibration on a large motor or pump mandates a shutdown
- A high rate of change in reactor temperature requires a shutdown
- High pressure at a spec break needs the source shutoff
If a PLC or other BPCS is available, it commonly provides only one trip execution. Adding a stand-alone process trip to the loop provides a redundant trip source, preventing common mode failure. Moore Industries’ SPA2 model is a high volume choice for this trip.
When a BPCS is not available, stand-alone alarm trips such as the SPA2, can take on the task. Hard alarm trips complement a PLC by providing redundancy, simple control, and critical safeguarding. Hard alarms are not exposed to adverse effects of common-mode failure because they maintain complete independence from the PLC or DCS.
- Accept a signal input from transmitters, temperature sensors and a wide array of other monitoring and control instruments
- Dual and quad alarm trip outputs
- Site- and PC-programmable