Mechanical Failure Blamed for Fire on Fishing Vessel
The National Transportation Safety Board released a Marine Accident Brief about the fire and sinking of the commercial fishing vessel Ole Betts Sea on March 18, 2018, approximately 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.
About 0545 on March 18, a rigman took the helm 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.
However, about a minute later, the vessel started shaking. While the rigmen retrieved the rig, small boomlike noises emanated from the engine room. The captain 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.
The captain went to the engine room door, located on the port side of the main deck, and slid the door open. Thick grayish smoke prevented him from entering, so he closed the door. The captain went to the wheelhouse and called another nearby fishing vessel on VHF radio to inform the other vessel’s captain that Ole Betts Sea was on fire.
About three minutes after the shaking began, it stopped, and the lights went out; yet the main engine continued to propel the boat. The crew donned lifejackets, and the captain decided it would be prudent to launch the rigid liferaft 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 liferaft, 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 accessway 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 liferaft with the dog. The captain and the other rigman jumped into the water and held onto the liferaft. At 0731, the crew of a nearby Good Samaritan vessel, the fishing vessel Sea King, notified the Coast Guard of the fire and, at 0740, took Ole Betts Sea’s crew aboard their vessel.
While the Ole Betts Sea continued to burn, the fishing boats Big Papa and Miss Maddie attempted to fight the fire by spraying water onto the burning trawler. About 1140, the fishing boats ceased their firefighting efforts due to the fire’s intensification. The fire continued to burn until about 2110, 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 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. 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 vibrations reported by the crew, investigators developed a likely cause for the initiating “boom,” heavy gray smoke, and subsequent explosion and fire that burned out of control. There was insufficient evidence to pinpoint the cause of the initial noise and source of gray smoke. Although it is feasible that they were caused by the batteries, switchboards, or battery charger exploding, it is 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, 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.
Further, because the shaking stopped before the propulsion diesel engine ceased operating and the vessel ceased forward movement, it is 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 is 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 (cutoff) valve, outside of the engine compartment. Depriving the fire of fuel, especially during the early stages of the incident, could have prevented further ignition of flammable materials, such as the fiberglass hull and bulkheads, and increased the likelihood of saving the vessel.