Hazop Study Guideword Checklists

Hazop Study Guideword Checklists

  GUIDEWORD CHECKLIST – Core set example

This core set of guidewords should be used for all process design Hazop studies. 

GUIDEWORD	DEVIATION	EXAMPLES OF POTENTIAL PROBLEMS
FLOW	NO/LESS	High pressure; stagnant lines, line/instrument tapping blockages, filter blockages
	MORE	Undesirable flow, leakages, high velocity/erosion, vents & overflows, draining/sampling, flexible failure, seal/gasket failure, environmental emissions, inventory minimisation / isolation, well barrier failure/testing
	REVERSE	Utilities contamination/overpressure, reverse rotation, NRV failure, vessel overfill
	MISDIRECTED	Unexpected routings, transfer errors, interlocks & locked valves, identification & labelling, operational flexibility/complexity
TEMPERATURE	HIGH	Elastomeric materials, corrosion, thermal expansion/creep, location of temperature probes, decomposition, personnel protection, fire
	LOW	Embrittlement, hydrates/freezing, flashing liquids, depressurisation, low ambient temperatures
PRESSURE	HIGH	HP/LP interfaces, hydraulic surge, explosive boiling, gas breakthrough, liquid overfill, compressor settle out, tube rupture, deadheaded pump, thermal expansion, chemical reaction, fire exposure, vent/relief blockages, restriction orifice corrosion / erosion / removal
LEVEL/ELEVATION	HIGH LOW	Vessel overfill, high static head Line routing, deadlegs, liquid accumulation, cavitation, gas blowby, loss of interface
COMPOSITION VISCOSITY/DENSITY	CHANGE	Contamination with air, water, liquids/gases/ solids, slugging,chemical additives, corrosion products, sand, mol sieve, lost circulating fluids etc
EROSION	HIGH	Localised failure, choked valves, straight tees, unbalanced flows
DEPOSITION	PROBLEMS	Radioactive scale, pyrophoric scale, sand, wax, asphaltenes hydrate, ice, debris etc
CORROSION	HIGH	Dissimilar materials, stress corrosion cracking, H2S, CO2 composition/contamination/temperature/pressure effects, blockages due to buildup of corrosion scale, under lagging corrosion, pitting, stray currents, SRB activity
SERVICES	FAILURE	Power, heating/cooling medium, instrument air, hydraulics, nitrogen/fuel gas purge
MAINTENANCE INSPECTION	PROBLEMS & REQUIREMENTS TESTING	Access, layout, isolation, draining/venting/ purging, pyrophorics/ radioactivity maintainability/reliability, lifting, vessel entry, pressure/leak/function testing, condition monitoring, spares
STARTUP/SHUTDOWN	PROBLEMS & REQUIREMENTS	Non-standard conditions, human errors Emergency shutdown requirements, sequential operations
OTHER		An opportunity for chairman to prompt team members to raise any other concerns.

11.1.2 GUIDEWORD CHECKLIST – Supplementary set

Guidewords should be selected from this supplementary set as appropriate to the nature of the system and scope of the Hazop. 

GUIDEWORD	DEVIATION	EXAMPLES OF POTENTIAL PROBLEMS
CHEMICAL	MORE/LESS	Unexpected chemical/biological reaction, incomplete reaction
REACTION / BIOLOGICAL FOAMING	PROBLEMS	Level /interface measurement problems
IMPACT	EXTERNAL	Dropped objects, small bore fittings. swinging loads, ships/helicopters
	INTERNAL	Pig operations, hydrate plug, loose internals
HAMMER	PROBLEMS	Steam hammer, hydraulic surge
VIBRATION	MORE	Fatigue failures, thermal well failures, critical speed, well movement
IGNITION	SOURCES	Uncertified equipment, static, hot surfaces
CATALYST	REGENERATION CHANGE	Sequential operation
VENTILATION	LESS	Gas accumulation, fumes, oxygen enrichment, oxygen deficiency, pressurisation
RELIABILITY	LOW	Instruments/equipment reliability
OPERABILITY	PROBLEMS	Equipment operability / suitability, ergonomics, system complexity/flexibility, potential for human error / exposure, instrument visibility, procedures, critical information/alarms presentation, response time/action, manning
HUMAN	FACTORS	Supervision, handover, training, clear responsibilities, remote/local control
SAMPLING	PROBLEMS	Provision of sampling/draining/venting facilities, routing
DRAINING/VENTING		Batch operation, human error, uncontrolled release, filter change
SIMOP's	PROBLEMS	Well intervention, drilling, well test, construction, commissioning / decommissioning, maintenance
LAYOUT/ACCESS	PROBLEMS	Maintenance, operations, emergency escape routes
CONSTRUCTION	PROBLEMS
COMMISSIONING	PROBLEMS
ENVIRONMENTAL	CONCERNS	Emissions/spills to air, land, water
HEALTH	CONCERNS	Toxic materials in process, additives, construction materials, sampling/draining/venting procedures. Noise, radioactivity
NOISE	HIGH	Pumps, compressors, engines, high velocities, chokes, vents, exhausts
CRACKING	PROBLEMS	Thermal decomposition, stress corrosion cracking, Brittle fracture, weld quality
RADIATION	THERMAL IONISING	Personnel protection, flare LSA Scale, nucleonic instruments
VELOCITY/SPEED	HIGH LOW	Erosion, noise Deposition
DRAWING	ERRORS
WEATHER	PROBLEMS	Severe weather conditions, high/low winds, high/low temperatures, tides, flooding, combined loads etc

11.1.3 GUIDEWORD CHECKLIST - Supplement set for sequential ops

These guidewords should be used when Hazop sequential operations (procedures) supplemented by a selection of guidewords from the preceding core and supplementary sets appropriate to the nature of the operations and scope of the Hazop. 

GUIDEWORD	DEVIATION	EXAMPLES OF POTENTIAL PROBLEMS
SEQUENCE STEP	OMITTED	Step not done, handover, split responsibilities
	INCOMPLETE	Step only partially completed or delayed
	VALVE ERRORS	Valve open or closed in error prior to/during step
	TOO SHORT/LONG	Operation completed too slowly or too quickly
	TOO LATE/EARLY	Insufficient or excessive delay before moving on to the next step or following completion of previous step
	WRONG ORDER	Step done out of sequence
	WRONG ACTION	An incorrect action substituted for the correct action
	EXTRA ACTION	Another action completed as well as the action intended
	SIMOPS	Any other simultaneous activity which may impact on the overall safety of the operations