Country: SPAIN - Europe

Location: ONSHORE

Incident Date: 15 May 2013   Time: ---

Type of Activity: Maintenance, inspection, testing

Cause: Explosions or burns

Function: Production

After a TEG (Triethylene glycol) low low level alarm at the natural gas dehydration unit, the unit was stopped and the operator waited 2 hours before opening the TEG inlet. A fire occurred when the TEG vapors, coming from inside the accumulator tank, reached the exhaust stack during the TEG refilling operation. The burner zone has restrictions for operator escape, although on this occasion the operator reached the TEG inlet cap from outside the zone and was not caught by the fire. The fire detector produced a level 1 emergency shut down and the fire was put out by the internal fire brigade without significant consequences.

Unsafe Acts:

• Opening the cap of TEG accumulator tank with vapors inside due to insufficient time for cooling the reboiler unit.
• Error in implementation of permit to work due to refilling operation being considered as routine.

Unsafe Conditions:

• The design of the unit directs the vapors coming out of the refilling inlet towards a hot spot.
• Combustion soot had accumulated inside the exhaust gas stack, up to 3/4 of the internal section, contributing to a longer time for cooling of the hot spots.

ROOT CAUSES:

• TEG inlet aiming to a hot spot is considered to be an error in design, causing that TEG vapor is directed to a hot spot when the inlet cap is opened.
• No written instructions were available, specifying how to perform the task (required isolations, time for cooling, unit operating condition, etc.)
• Deficient inspection and maintenance plan: the periodic inspection of exhaust pipe for burners was not included in plan.

• The TEG inlet shall be checked/modified to ensure that vapors are evacuated to a safe place.
• A technical instruction shall be prepared to describe TEG refilling operation.
• Include the inspection of exhaust pipe for all the units with burner in the inspection and maintenance plan.

Safety Alert number: 249
IOGP Safety Alerts http://safetyzone.iogp.org/

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