November 25, 2013 | Mark Paradies

Monday Accident & Lessons Learned: OGP Safety Alert – TEG FIRE AT GAS DEHYDRATION UNIT

This is a safety alert passed along from the The International Association of Oil & Gas Producers (OGP) – OGP Safety Zone website.

OGP Safety Alert

TEG FIRE AT GAS DEHYDRATION UNIT

Country: SPAIN – Europe
Location: ONSHORE : Other fixed installation
Incident Date: 15 May 2013  Time: —
Type of Activity: Maintenance, Inspection, Testing
Type of Injury: 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.

Front and side view of the dehydration unit. TEG inlet design aiming to hot spot.             Safety Safetyalerts Alert Images 249 S249 Img2

What Went Wrong?:

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.

Dehydration unit involved in the incident. Detail of TEG inlet.     Safety Safetyalerts Alert Images 249 S249 Img1

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.

Corrective
Actions and Recommendations:

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
OGP Safety Alerts http://info.ogp.org.uk/safety/

Disclaimer

Whilst every effort has been made to ensure the accuracy of the information contained in this publication, neither the OGP nor any of its members past present or future warrants its accuracy or will, regardless of its or their negligence, assume liability for any foreseeable or unforeseeable use made thereof, which liability is hereby excluded. Consequently, such use is at the recipient’s own risk on the basis that any use by the recipient constitutes agreement to the terms of this disclaimer. The recipient is obliged to inform any subsequent recipient of such terms.

This document may provide guidance supplemental to the requirements of local legislation. Nothing herein, however, is intended to replace, amend, supersede or otherwise depart from such requirements. In the event of any conflict or contradiction between the provisions of this document and local legislation, applicable laws shall prevail.

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