A Nov. 12, 2016, fire on a Gulf of Mexico offshore platform, which injured three Wood Group contract employees, broke out when a flammable gas mixture that was released through the thief hatch on the dry oil tank, migrated into the left fire tube, where it contacted either the left fire tube flame or the left burner pilot flame, a US Bureau of Safety and Environmental Enforcement investigation concluded.
This flame likely propagated through a gap in the mating flange between the left flame arrestor housing and the heater treater, igniting the flammable gas mixture in the surrounding atmosphere on LLOG Exploration Offshore LLC’s Grand Isle Block 115 “A” Platform in the gulf, according to the report released by BSEE on Aug. 30.
The report said that since production resumed on the platform in March 2016 following structural modifications, excessive basic sediment and water (bs&w) caused frequent problems with maintaining production. In early November, LLOG installed a steam unit, which resolved some of their bs&w issues. However, on the day of the incident, a mechanical malfunction occurred in the steam unit, resulting in an excessive emulsion pad in the heater treater that prevented LLOG and Walter Oil & Gas (WOG) from producing sales quality oil.
“To address this issue, crews usually drained the emulsion pad from the heater treater to one of the oil tanks on the cellar deck below, and then used a bucket to batch treat the emulsion with a chemical emulsion breaker,” the report said. “The crew involved in the incident was preparing to troubleshoot the emulsion pad when the fire occurred. They made no attempt to isolate the heater treater, nor did they secure the fire tube burners.”
Without draining the emulsion pad, one operator, who was adjacent to the heater treater flame arrestors on the platform’s main deck, prepared to batch treat the dry oil tank using a hose from a chemical tank on the main deck to the dry oil tank on the cellar deck below, it continued. Another operator opened a hatch on the top of the dry oil tank to receive the hose, which released a flammable vapor cloud that extended upward to the main deck, the report said.
“Within a minute of the hatch being opened, the operator on the main deck, as well as another operator who had just walked up to him, described witnessing a flame coming from the general location of the heater treater flame arrestors. The flame ignited the existing flammable vapor cloud in the vicinity of the heater treater flame arrestors,” it said.
Extent of injuries
The report said the operator preparing to batch treat was engulfed in flames but managed to escape the fire by running toward the platform’s southwest corner. The operator on the cellar deck felt the flame around him before closing the hatch and jumping down to safety.
The operator who had just arrived fell backward, got up, pushed the platform emergency shutdown (ESD) button and announced the fire over the radio. Both operators on the top deck, as well as other personnel on shift throughout the platform, responded to assist with extinguishing the fire. Individual accounts indicated that the fire lasted anywhere from a few seconds to several minutes, BSEE’s report said.
The three injured operators suffered a combination of first and second-degree burns to their hands, arms, and faces, the most severe of which were to the operator preparing to batch treat, it continued. Platform personnel assisted with first aid treatment while the Person-in-Charge (PIC) called for evacuation of the injured employees to a hospital on shore. All three were treated and released within 2 days of the incident.
Indirect causes of the fire included the failure of personnel to sufficiently mitigate hazards, a lack of sufficient engineering controls, and the gap in the flame arrestor-heater treater mating flange which was likely caused by improper installation and assembly of the mating flange, BSEE’s investigators found.
Other contributing factors included a failure to follow recommendations by the original equipment manufacturer (OEM), a failure by personnel to adhere to permitting requirements, and an insufficient hazard analysis performed to eliminate the emulsion pad because the incident crew not only neglected to perform a job safety analysis, but also failed to hold a prejob safety meeting.
To avoid similar events in the future, BSEE’s investigators recommended that operators and contractors:
• Consider the location(s) of fired elements relative to potential gas releases when performing facility-level hazard analyses.
• Consider the use of permanent containment systems for vessel draining and chemical treatment.
• Consider conducting visual inspections of natural draft burners, ensuring airtight integrity between flame arrestors and fire tubes.
• Consider the use of a portable gas detector when operating in the vicinity of fired vessels.
• Consider increasing operator supervisory presence when using contractor-employed supervisory personnel during nonroutine operations.
• Consider ensuring production standard operating procedures (SOPs) are used for site specific equipment and conditions.
• Ensure operators are familiar with, and adhere to, the original equipment manufacturer’s instructions regarding start-up, operations, maintenance, and inspection of fired vessels and associated safety devices.
• Consider instituting applicable industry standards into inspection programs, SOPs, and safe work practices (SWPs).
• Ensure all contractor personnel engaged in production operations know the operator’s SWPs.
• Ensure that all company, contractor, and visiting personnel properly wear protective personnel equipment where the potential exists for thermal exposure from fire, and that the protective equipment selected for the job reflects the job’s probable and possible hazards.
“The panel’s recommendations underscore the importance of placing safety first in every job being undertaken on a facility—no matter how routine,” BSEE Director Scott A. Angelle said in an Aug. 29 memorandum to Harold Griffin, who chaired the investigation; Gulf of Mexico Regional Director Lars Herbst, and Offshore Regulatory Programs Office Chief Doug Morris.
Angelle said the report also draws attention to the importance of having up-to-date hazard analyses and associated work permits. “Finally, given the significant burn injuries the personnel sustained, the report show just how important proper protective personnel equipment is during day-to-day operations,” he said.
BSEE also issued a safety bulletin to operators on Aug. 30 with recommendations based on the investigation’s findings.
Contact Nick Snow at [email protected].