Alarm or interlock? Stop letting HMI do control

Last week a compressor train tripped and everyone wanted a new smart alarm and a faster trend. The HMI fault log showed 600 chattering events from one oily, vibrating lube oil transmitter. Meanwhile the header pressure actually sagged below the bearing spec for 4 seconds. Well, there is your problem.

Alarms are for awareness; interlocks are for physics. If a condition can eat bearings, spin a seal, or flash a film in seconds, you do not page an operator, you block the start and trip the equipment. Put in a clear permissive matrix, latch it, fix the sensor placement, add proper deadband and debounce, and if it is critical, give it redundant transmitters with voting or rate-of-change checks. And setpoints should be based on hardware limits, not what felt safe last shutdown.

My rule: if I would not trust a tired human at 3 a.m. to save it, I just interlock it. How do you draw the line between alarm and hard trip in your plants?