Hazop Guide Words: NO
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 |
|---|---|---|---|---|---|---|---|---|---|---|
| NO | flow#heat_exchanger#cooling_loss | cooling_loss | Loss of cooling water to heat exchanger | possible | heat_exchanger | flow | serious | Cooling water pump failure; cooling tower failure; blocked cooling water supply; isolation valve left closed during maintenance | Process temperature rise; runaway reaction if cooled reactor; overpressure; product degradation | Cooling water low-flow alarm; process high-temperature trip; backup cooling (redundant pump); emergency air cooler |
| NO | flow#pipe#general | general | No flow in pipe or line | possible | pipe | flow | serious | Pump failure; blocked valve; blocked filter/strainer; pipe blockage; loss of suction; operator error closing block valve | Process starvation; overheating of downstream equipment; loss of product; pump cavitation on restart; downstream vessel runs dry | Low-flow alarm (FAL); pump running indication; flow transmitter with trip; SOP for minimum flow |
| NO | flow#pump#pump_delivery | pump_delivery | Pump fails to deliver flow | possible | pump | flow | serious | Pump motor failure; seal failure; cavitation; suction strainer blocked; loss of prime; shaft failure | Loss of process flow; overheating of downstream equipment; loss of cooling; product loss | Flow switch (FSL) on pump discharge; pump running indication; high-temperature alarm on pump casing; spare pump with auto-start |
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