The crew closed the engine room down and extinguished the fire with a Halon gaseous fire-smothering system.
In its report into what happened, the Transport Accident Investigation Commission discovered it was likely caused by a combination of factors, primarily around maintenance carried out on the vessel five weeks earlier.
It found a connector wasn't tightened enough when fitted into the accumulator by shore-based contractors.
It caused vibration and resonance by the machinery and propulsion system, while there was also a "loose fit" between the male thread on the connector and the female thread of the accumulator.
Once the steel-on-steel connection between the two components was lost, it caused more vibration, allowing the accumulator to loosen.
The bladder in the accumulator then failed, which meant it wasn't doing its job of absorbing the pulsing pressure on the fuel system.
A lack of support bracket eventually saw it dislodge.
The commission said there were several learnings from the incident and issued several recommendations for Maritime NZ to distribute.
It said it was important that repair and maintenance were performed under controlled conditions, including following appropriate procedures for tagging out, checking, testing, and signing off each task, particularly when working on safety-critical systems.
The commission said vibration in engine rooms "can be problematic" and said components - particularly those that were safety-critical - needed to be secured against vibration to guard against loosening, wearing, cracking, or destruction.
"It is important that devices for disconnecting systems remotely are routinely tested to ensure that they function correctly during an emergency."
In an emergency, crew needed to fully consider the important elements of command and control, along with establishing good communications.
The crew also needed to be aware that the longer they delayed activation of a fixed gaseous fire-extinguishing system, the higher the risk that fire will partially or fully deem the system's mechanisms inoperable.
The commission recommended that Maritime New Zealand ensure the trawler's owner - Talleys - install a new system that complied with current maritime rules and put in place extra measures to manage the risk created by the limitations of the current fire-extinguishing system until a new system was installed.
It also recommended that Talley's introduce a system for managing contractors working on board, including making sure they sign off for each task, highlight risks posed to the contractors or crew, and, where applicable, testing to ensure the repaired system was still fit for purpose.
Responding to the recommendations, Talleys said it had prepared a draft duties framework document to manage contractors at layups and turnarounds, using the WorkSafe Good Practice Guideline.
"In addition to this, Talley's is engaging in detailed consultations with shore staff, vessel staff, contractors, and other stakeholders, outcomes of which will help us to understand where additional processes may be required to support their current processes."
The document would then be distributed to Talley's staff, contractors, and stakeholders, against which current activities could be benchmarked and modified if required.
They hoped to complete the draft framework in June, and its detailed processes by the end of this month.
Also, all contractors would now report to a chief or second engineer when getting on and off the vessel. Staff who issue permits would also have their qualifications or competencies reviewed.
