Hazop Guide Words: REVERSE
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 |
|---|---|---|---|---|---|---|---|---|---|---|
| REVERSE | flow#control_loop#general | general | Reverse flow through control valve (flow in wrong direction) | unlikely | control_loop | flow | moderate | Control valve installed backwards; downstream pressure exceeds upstream; flow reversal in system | Incorrect process conditions; off-spec product; control loop instability; potential damage to valve internals | Flow direction arrow on valve; installation inspection; bidirectional valve specification where required; flow transmitter alarm |
| REVERSE | flow#pipe#general | general | Backflow in pipe | unlikely | pipe | flow | serious | Check valve failure; loss of upstream pressure; downstream overpressure; operator error connecting lines; pump trip with high back-pressure | Cross-contamination of process streams; damage to rotating equipment; utility contamination (cooling water ingress to process) | Check valve; non-return valve (NRV); high-pressure alarm on upstream; interlock preventing reverse operation |
| REVERSE | flow#pump#general | general | Backflow through pump (pump trips with discharge pressure high) | unlikely | pump | flow | moderate | Pump trip with high back-pressure; check valve failure on pump discharge; loss of prime; reverse rotation on restart | Damage to pump internals; back-contamination of suction vessel; loss of prime | Check valve on discharge; non-return valve; pump low-flow alarm; motor current monitoring for reverse rotation |
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