guideword stringclasses 7
values | meaning stringlengths 37 81 | parameter stringlengths 4 18 | example_deviation stringlengths 21 81 | example_cause stringlengths 73 112 | example_consequence stringlengths 86 150 | example_safeguard stringlengths 104 194 |
|---|---|---|---|---|---|---|
NO/NOT | Complete negation of the design intent (the intended event does not occur at all) | Flow | No flow in process pipe to reactor | Control valve CV-101 fails closed; pump P-201 fails to start; blocked line upstream | No feed to reactor — potential runaway if exothermic reaction already in progress; catalyst damage | Low-flow alarm FAL-101; reactor temperature high alarm TAH-201; interlock on reactor feed shutdown; pump duty-standby auto-changeover |
NO/NOT | Complete negation of the design intent | Reaction | No reaction in batch vessel | Catalyst not loaded; incorrect raw material; temperature too low to initiate | Off-spec batch; undetected unreacted hazardous material in product stream; downstream explosion risk on concentration | Batch recipe interlocks; temperature confirmation before heat release; in-process quality sample; production hold and test procedure |
NO/NOT | Complete negation of the design intent | Level | No level in separator | Bypass valve left open draining vessel; upstream failure; drain left open | Loss of liquid seal in separator — gas breakthrough to liquid outlet; overpressure in downstream liquid line; downstream fire | Low-level alarm LAL-201; low-low level shutdown LSL-201LL; operator checklist for drain valve position before startup |
MORE | Quantitative increase above the design intent | Flow | More flow through heat exchanger shell side | Upstream control valve CV-202 fails open; increased upstream pressure; pressure regulator failure | Tube overloading; elevated pressure on tube-side — tube failure; flammable or toxic material release to cooling water or atmosphere | High-flow alarm FAH-202; pressure relief valve PRV-HX101 on shell; shell inspection programme for tube integrity |
MORE | Quantitative increase above the design intent | Temperature | High temperature in reactor | Excessive steam supply; blocked cooling water; runaway exothermic reaction; loss of agitation | Decomposition; runaway reaction; vessel overpressure; BLEVE potential for flammable material; toxic gas release | High temperature alarm TAH-301; high-high temperature shutdown TSH-301HH (trips steam supply + activates quench); relief valve RV-R01; agitator low-speed trip |
MORE | Quantitative increase above the design intent | Pressure | High pressure in gas storage vessel | Thermal expansion (solar radiation); upstream compressor runaway; blocked outlet; external fire (BLEVE scenario) | Vessel failure; BLEVE; fragment projection; vapour cloud explosion; multiple casualties | Pressure relief valve PSVX-01; rupture disk upstream of PSV; high-pressure alarm PAH-401; fire-fighting water system; vessel support design for fire case |
MORE | Quantitative increase above the design intent | Level | High level in atmospheric tank | Inlet control valve fails open; level transmitter failure; operator inattention during filling | Overflow of flammable / toxic material; tank berm exceedance; environmental spill; fire risk | High-level alarm LAH-501; high-high level shutdown LSH-501HH (closes inlet valve); independent level gauge (sight glass); overfill protection device per API 2350 |
MORE | Quantitative increase above the design intent | Concentration | Higher concentration of hazardous component in reactor feed | Sampling error; supplier batch variation; metering error; wrong raw material loaded | Runaway reaction; product out of spec; potential detonation for peroxide-forming substances | Inlet analyser AIC-601; feed ratio control; batch record verification; raw material QC certificate check |
LESS | Quantitative decrease below the design intent | Flow | Less flow in cooling water to reactor jacket | Cooling water pump degradation; partial valve closure; fouling in cooling water circuit | Inadequate heat removal; reactor temperature rise; runaway risk; potential decomposition of thermally sensitive material | Low cooling water flow alarm FAL-701; temperature rise alarm TAH-301; interlock on reactor agitator speed and steam supply |
LESS | Quantitative decrease below the design intent | Temperature | Low temperature in cryogenic storage vessel | Refrigeration system failure; excessive heat ingress; warm product fill; vacuum jacket failure | Vapour generation; pressure build-up; relief valve lifting; potential vessel embrittlement if temperature falls below design minimum metal temperature | Low temperature alarm TAL-801; high pressure alarm PAH-401; refrigeration duty-standby; boil-off gas management system; vessel material specification for cryogenic service |
LESS | Quantitative decrease below the design intent | Level | Low level in suction vessel | Outlet valve opens unexpectedly; downstream demand increase; metering error | Pump cavitation; loss of flow downstream; potential air ingestion; product quality impact; pump seal failure | Low-level alarm LAL-201; pump auto-stop on low-low level LSLL; inlet control valve override to maintain minimum level |
LESS | Quantitative decrease below the design intent | Pressure | Low pressure in reactor (vacuum scenario) | Condenser flooding; outlet valve opens; steam condensation with no vent; cold snap with no nitrogen padding | Vessel designed for pressure operation only — implosion; ingress of air into flammable atmosphere; oxygen contamination of product | Vacuum relief valve VRV-R01; nitrogen padding system with N2 supply alarm; pressure monitoring with low-pressure alarm PAL |
AS WELL AS | Qualitative modification — something in addition to what was intended | Composition / Flow | Contaminant in process stream — water in anhydrous reactor feed | Condensation in delivery hose; improper purging after hydrotest; water hold-up in dead leg | Decomposition of water-sensitive catalyst; violent reaction with moisture-reactive material; steam generation causing overpressure | Moisture analyser on feed; purge and dry-out procedure after maintenance; line draining checklist; dead-leg elimination programme |
AS WELL AS | Qualitative modification — additional hazardous material present | Two-phase flow | Gas and liquid carried together in normally liquid line | Vaporisation due to pressure drop; gas ingestion at pump suction; dissolved gas release | Surge and slug flow causing pipe vibration; fatigue failure; flow measurement error; pump damage; high vibration and noise | Separator upstream of pump; vortex breaker; flow pulsation dampener; vibration monitoring on pump and critical pipework |
PART OF | Qualitative modification — only part of the intended event occurs | Composition | Partially complete chemical reaction — low conversion | Catalyst poisoning; insufficient residence time; low temperature; reactant ratio imbalance | Unreacted hazardous material in product stream; downstream processing of out-of-spec stream; potential for secondary undesired reaction | In-line analyser on reactor outlet; batch sample testing with hold procedure; residence time interlock on continuous reactor |
PART OF | Only part of intended transfer completes | Flow (partial) | Partial transfer of batch to next vessel — incomplete drain | Pipe partially blocked; valve does not fully open; pump operates below design duty | Wrong batch composition in receiving vessel; heel material causes contamination in next batch | Level confirmation in source and destination vessels before process step sign-off; batch management system check |
REVERSE | Logical opposite of the design intent | Flow | Reverse flow in single-direction line | Downstream pressure higher than upstream; pump fails while line is pressurised; siphon effect on drain line | Back-flow of product (possibly hazardous) into wrong vessel or to atmosphere; contamination; overfill | Non-return valve (check valve) NRV-101; backflow prevention device; interlock preventing simultaneous opening of inlet and outlet valves; reverse flow alarm in DCS |
REVERSE | Logical opposite — reversed rotation or direction | Rotation | Pump / compressor reverse rotation | Single phasing of motor; incorrect phase connection after maintenance; loss of supply phase | No flow or reduced flow; potential seal failure; motor overheating; damage to impeller | Anti-rotation device on pump; phase rotation indicator on motor starter; electrical protection relay; pre-start check procedure |
OTHER THAN | Complete substitution — something completely different from design intent | Material / Service | Wrong material charged to reactor | Label mix-up; look-alike containers; wrong tank connection; material substitution without MOC | Uncontrolled reaction; toxic gas release; equipment damage; potential fatality; fire/explosion | Material labelling and colour-coding; two-person verification on material loading; unique connection fittings (key locks); MOC procedure; pre-charge verification checklist |
OTHER THAN | Deviation in utility service — wrong service applied | Utility | Wrong utility connected — instrument air connected to nitrogen line or vice versa | Physical connection error during maintenance; connector not uniquely designed; labelling failure | Instrument air in purge system — oxygen ingress into inerted system; fire/explosion; or nitrogen in breathing air line — asphyxiation | Unique connection fittings for different services; colour-coding of pipe and hose connections; cross-connection prevention programme; pressure and composition check after reconnection |
OTHER THAN | Operating mode deviates from intended | Operating mode | Maintenance mode operated instead of production mode (or vice versa) | Logic controller fault; software update error; HMI display error; operator selection error | Safety instrumented system bypassed; safety interlocks defeated without authorisation; process run outside safe operating limits | Access control on operating mode selection; mode change requires authorised sign-off; SIS bypass log and management procedure (IEC 61511 management of functional safety); proof testing programme |
HAZOP Guidewords Reference 2026 — IEC 61882 with Node Examples
HAZOP guidewords reference following IEC 61882:2016 and CCPS guidance. 7 standard guidewords (NO/NOT, MORE, LESS, AS WELL AS, PART OF, REVERSE, OTHER THAN) applied to key process parameters (flow, pressure, temperature, level, composition, reaction, rotation, operating mode) with ~20 worked examples each providing: deviation, cause, consequence, and safeguard.
Dataset details
- Publisher: SmartQHSE Ltd (https://www.smartqhse.com)
- License: CC BY 4.0 -- please cite with link to https://www.smartqhse.com
- Format: CSV (UTF-8)
- Schema: see data.csv first row (header)
- DOI: 10.5281/zenodo.20171699 -- permanent Zenodo citation
- Update cadence: annual or on regulatory change
- Canonical home: https://www.smartqhse.com/datasets
Suggested citation
SmartQHSE Ltd (2026). HAZOP Guidewords Reference 2026 — IEC 61882 with Node Examples [dataset]. Zenodo. https://doi.org/10.5281/zenodo.20171699
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This dataset is published for reference, training, and research. Regulatory text and action levels are summarised; consult the authoritative source listed before basing operational or compliance decisions on this dataset. SmartQHSE Ltd accepts no liability for errors or omissions.
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