We've talked about reading error and sample accuracy when comparing the use of Flammability (FTA) Analyzers and Flame Ionization (FID) Detectors in process applications. Today let's talk about a great feature: fail-safe.
"A fail-safe or fail-secure device is one that, in the event of a specific type of failure, responds in a way that will cause no harm, or at least a minimum of harm, to other devices or danger to personnel."
Because an analyzer would allow a process to operate above 25% LFL, it is vital that any failure of that analyzer results in a fail-safe condition.
Flammability analyzers are fail-safe. A fault relay de-energizes whenever any of the following occur:
- controller electrical failure
- loss of system power
- loss of heat
- loss of flow through the flame cell
- downscale readings caused by loss of flame or fuel
Flame ionization detectors are NOT fail-safe because the capillaries in the sample train can clog gradually without any warning or relay action.