Fire on shrimp trawler was result of mechanical failure, says NTSB

A fire on and subsequent sinking of shrimp trawler Ole Betts Sea (IMO 7943495) was a mechanical failure of the generator’s diesel engine, which led to a fuel-fed fire that burned out of control, according to the US National Transportation Safety Board (NTSB) , which has released a Marine Accident Brief about the incident on March 18th 2018

The fire occurred about 18 miles northeast of the island of Garden Key, Dry Tortugas, Florida. The crew of three abandoned the vessel, which suffered a total loss valued at $200,000.

Before getting under way on March 13th for the voyage that would result in the vessel sinking, the captain performed a pre-departure check of the vessel and found all in good order. Until March 18th all was found to be in good order.

At dawn on the morning of March 18th a rigman took the helm during the last trawl so that the captain could rest. About a half hour later, while the vessel was proceeding at idle speed (about 2.5 knots), the rigman heard something that sounded like a small boom or heavy thud. The captain returned to the wheelhouse when he heard the sound and told the rigmen to pull in the nets and gear. Lighting remained on and the vessel’s main engine continued to propel the boat.

About a minute later, the vessel started shaking. While the rigmen retrieved the rig, small boomlike noises emanated from the engine room.

The captain stated that he attempted to move the throttle to neutral and stop the main propulsion engine from the wheelhouse, but he could not do either. The vessel continued making a speed of about 2.5 knots.

While the rigmen worked at retrieving the fishing gear, the captain went to the engine room door, located on the port side of the main deck, and slid the door open. Thick greyish smoke prevented him from entering, so he closed the door.

The captain called a nearby fishing vessel on VHF radio to report that Ole Betts Sea was on fire.

About three minutes after the shaking began, it stopped, and the lights went out; the main engine continued to propel the boat at idle speed.

The crew donned lifejackets and the captain decided to launch the rigid life raft in order to be ready to evacuate the vessel should the fire grow. To stop the boat’s movement so that the crew could safely deploy the life raft, the captain ordered the rigmen to drop the trawl rig and anchor.

He then went to the forward hatch on the main deck, lowered discharging dry-chemical fire extinguishers into the forepeak compartment (which was connected by an open access way to the engine room) and closed the hatch in an attempt to extinguish the fire. He could not access the engine room further aft due to heavy smoke and heat.

The vessel did not have, nor was it required to have, a fixed firefighting system for the engine room. The fire did not abate and, a short time later, a large explosion occurred. After this explosion, thick black smoke emerged from the engine room and the vessel stopped.

One rigman abandoned the boat into the life raft with the dog. The captain and the other rigman jumped into the water and held onto the life raft.

At 07:31 105 minutes after the first incident, the crew of fishing vessel Sea King notified the Coast Guard of the fire. At 07:40 they took Ole Betts Sea’s crew aboard their vessel

The Ole Betts Sea continued to burn and fishing boats Big Papa and Miss Maddie attempted to fight the fire by spraying water onto the trawler.

About 1140, nearly six hours after the first incident, the fire had intensified to the extent that the fishing boats ceased their firefighting efforts. The fire continued to burn until about 21:10, when the crew of an on-scene Coast Guard cutter, the Charles David Jr, witnessed a large explosion, and the Ole Betts Sea sank.

The Ole Betts Sea was not salvaged, and thus it was not possible to determine the exact cause of the fire that sank the vessel. However, based on the sequence of events, sounds, and two Engine blow-bys, it was observed that the events were consistent with wear to the piston rings or cylinder liners allowing partially consumed fuel, air, and moisture to escape the cylinder and to enter the crankcase.

When expelled from the engine, the blow-by is evidenced by darker emissions from the vessel’s stack.

There was insufficient evidence to pinpoint the cause of the initial noise and source of grey smoke. Although it was feasible that they were caused by the batteries, switchboards, or battery charger exploding, it was more likely that the cause was a mechanical failure in either the Caterpillar propulsion diesel engine or the generator’s Detroit diesel engine.

Considering the shaking of the vessel that occurred about a minute after the initial “boom” noise, investigators believed that the only pieces of engine room equipment large enough to generate the type of vibration described by the crew were the diesel engines or propulsion shafting.

Therefore, the newly installed refrigeration unit for the fish hold was eliminated as the source of the initial explosion.

Further, because the shaking stopped before the propulsion diesel engine ceased operating and the vessel ceased forward movement, it was believed that the shaking was caused by a failure in the diesel engine driving the generator.

Because lights continued to operate until the vibration (diesel generator) stopped, it was unlikely that the generator itself failed.

When the large explosion occurred, thick black smoke spewed from the engine room, indicating a fuel fire. The fire was likely fed by diesel oil from a failed fuel line to the propulsion or generator diesel engines.

Investigators noted that there was no way for the crew to shut off the fuel flow to the diesel engines, such as a remote quick-closing (cut-off) valve, outside of the engine compartment. NTSB said that depriving the fire of fuel, especially during the early stages of the incident, could have prevented further ignition of flammable materials—such as the fibreglass hull and bulkheads—and increased the likelihood of saving the vessel.

NTSB commended that the crewmembers were prepared to abandon the vessel, and noted that their timely donning of lifejackets ensured that everyone was safely recovered after entering the water.

Therefore the National Transportation Safety Board attributed the loss to a mechanical failure of the generator’s diesel engine, which led to a fuel-fed fire that burned out of control.

1979-built, USA-flagged, 114 gt Ole Betts Sea is owned by Cap’n Bozo Inc of Florida, US, and operated by Trico Shrimp Co.

https://www.ntsb.gov/investigations/accidentreports/pages/MAB1905.aspx