Hazop Guide Words: EARLY
HAZOP guide words and deviations — IEC 61882:2016 guide words applied to common process parameters across node types (pipe, vessel, reactor, heat exchanger, pump, compressor, control loop, batch step), with typical causes, consequences, and safeguards
| guide word | deviation key | context | deviation description | likelihood class | node type | process parameter | severity class | typical causes | typical consequences | typical safeguards |
|---|---|---|---|---|---|---|---|---|---|---|
| EARLY | time#batch_step#general | general | Step or action performed earlier than scheduled in batch sequence | unlikely | batch_step | time | serious | Operator anticipation error; incorrect batch recipe loaded; timer malfunction; automatic sequencer fault; interlock bypass | Reaction mixture not yet ready; reactant added before heat-up complete; quench before reaction finished; product off-spec; overpressure | Batch management system (BMS) with step-by-step interlock; operator confirmation at each step; independent timer verification |
| EARLY | time#batch_step#hold_termination | hold_termination | Early termination of reaction hold time in batch sequence | unlikely | batch_step | time | moderate | Operator error; BMS timer malfunction; incorrect timer setpoint; time drift in control system | Incomplete conversion; off-spec product; unreacted raw material carried forward; potential hazard from incompletely consumed reactive material | BMS hold-time interlock requiring both time AND conversion confirmation; operator checklist; analytical release before step proceed |
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