Table 3.

HAZOP table based on (CCPS, 2001).

Pos.	Deviation	Causes	Identified	Consequence	Identified	Safeguard/Recommendations	Identified
0	High level	Flow from tank truck not discontinued before tank capacity has been reached	Yes	High pressure	Indirect	Level indication with high-level alarm (audible in the control room)	Yes
		Inventory control error – truck arrives before needed	Yes			Hexane unloading procedures with a checklist that includes checking field reading of tank before unloading	Other
1	Low level	Inventory control error – truck arrives too late	Yes	No safety consequences – potential process interruption if not refilled before the downstream feed tank is empty	Yes	–	Other
		Low flow or no flow – line from the tank truck to hexane storage tank T-301 through hexane unloading pump	Yes
2	High temperature	No credible causes identified	Other	–	Other	–	Other
3	Low temperature	Low ambient temperature while there is water contamination in the tank	Indirect	Possible freezing of accumulated water in the heel of the tank or the tank's drain line or instrument lines, resulting in fracture of the drain line and loss of containment	Indirect	–	Other
4	High pressure	High level	Other	Release of hexane through the relief valve into the tank's dike	Yes	–	Other
				Fire hazard affecting a large area if not contained by the dike	Yes
				Loss of containment (if the overpressure cause exceeds the tank pressure rating)	Yes
5	Low pressure	Tank blocked in before cooldown, following steam-out	Yes	Equipment damage resulting in a collapse of the tank under a vacuum	Yes	Standard procedures for steam-out of vessels	Other
6	High concentration of contaminants (Other than composition)	Water not completely drained following a steam-out or washout	Yes	Possible freezing of accumulated water in the tank during a period of low ambient temperature	Yes	–	Other
		High concentration of contaminants – line from the tank truck to hexane storage tank T-301 through hexane unloading pump	Yes
7	Loss of containment (Elsewhere flow)	Corrosion	Partially	Release of hexane	Yes	Operation/maintenance response as required, including isolation if needed	No
		Erosion
		External fire				Capability to manually isolate the tank	No
		External impact
		Gasket, packing or seal failure				Periodic non-destructive inspection per API recommended practice and ASME code	Yes
		Improper maintenance
		Instrument or instrument line failure		Fire hazard affecting a large area particularly if the capacity of the dike is exceeded	Yes	Relief valve that discharges to the tank's dike	Yes
		Material defect
		Sample station valve leaking				Dike sized for 1.5 times the capacity of the tank	Yes
		Vent or drain valve leaking
		Low temperature				Emergency response procedures	No
		High pressure (if the overpressure cause exceeds the equipment pressure rating)