Hazop Guide Words: OTHER_THAN
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 |
|---|---|---|---|---|---|---|---|---|---|---|
| OTHER_THAN | composition#vessel#general | general | Wrong material or entirely different composition in vessel | unlikely | vessel | composition | catastrophic | Line-up error; incorrect raw material delivered; labeling error; cross-contamination from adjacent process | Undesired or runaway reaction; product contamination; equipment corrosion; toxic or flammable material release | Material verification by analysis; positive material identification (PMI); operator two-check procedure; MOC procedure for material changes |
| OTHER_THAN | composition#vessel#utility_error | utility_error | Wrong utility connected — steam instead of nitrogen for vessel blanketing | unlikely | vessel | composition | serious | Line misidentification; manifold cross-connection; label error; color-coding not followed | Steam condensation creates vacuum; vessel implosion; oxygen ingress if inert blanket lost; water contamination of process | Physical segregation of utility headers; line labels; operating procedure verification step; check valve on inert gas inlet |
| OTHER_THAN | flow#control_loop#general | general | Control loop controls wrong variable (cross-wiring or misconfiguration) | unlikely | control_loop | flow | serious | Instrument cross-wiring during installation; incorrect tag assignment; loop check failure; software configuration error | Process runs uncontrolled; wrong variable manipulated; vessel overfill or underfill; temperature or pressure excursion | Pre-startup safety review (PSSR); loop checkout procedures; functional safety testing; SIL assessment for critical loops |
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