Pump failures ahead of pipeline leak

The pipeline that carries fuel from the Marsden Pt Oil Refinery experienced an ‘‘emergency shutdown’’ just two hours before it broke on September 14, triggering the Auckland fuel crisis, owner Refining NZ has confirmed.

Refining NZ spokesman Greg McNeill said the emergency shutdown was caused by a maintenance worker who accidentally triggered a fire alarm at a pumping station part-way along the 170km pipeline.

Two of the three pumps that were installed part-way along the pipeline failed to restart when the refinery began pumping fuel back through the pipeline about 20 minutes later.

That caused a pressure rise at some points, including at Ruakaka where the already-weakened pipeline broke later that morning, spilling 70,000 litres of jet fuel, according to a report engineers WorleyParsons provided to Northland Regional Council.

The council made no reference to the incident in the body of its own final report into the fuel leak published in November.

The blame for the leak – which took 10 days to fix and resulted in more than 100 cancelled flights at Auckland airport – has fallen on an unknown swamp kauri log hunter.

They are believed to have gouged the pipeline with a digger some time after July 2014, which was when the condition of the pipeline was last fully tested by running a device called a ‘‘pig’’ through the pipe.

But Refining NZ would not say whether it thought the pump failures were the ‘‘final straw’’ that triggered the rupture.

Refining NZ had also increased the maximum pressure at which the pipe was certified to operate from 70bar to 87bar in August so it could pump more fuel down it.

The company would not say whether it believed the pipeline might have held out until 2019 had the August pressure rise or the pump failures not occurred. That is when the next scheduled pig run should have alerted it to the digger damage.

McNeill explained it did not want to pre-empt a government inquiry announced by Energy and Resources Minister Megan Woods.

A spokesman for Woods said yesterday that officials were continuing to consult on the draft terms of reference for the inquiry.

WorleyParsons’ report said the events following the emergency shutdown on September 14 increased pressure at the point where the pipeline subsequently ruptured to about 82bar.

That was about 6bar above the normal pressure at that point along the pipeline, but still ‘‘significantly below’’ its maximumallowable operating pressure of 90bar, it said.

A separate engineering report showed Refining NZ was annually testing the cathodic protection of the pipeline, including during the period between the pipeline being damaged and its rupture.

The main purpose of cathodic protection is to protect metal from corrosion.

However, in some applications, routine testing of cathodic protection to ensure it is working can also detect damage to the coating of the metal it is protecting.

McNeill said Refining NZ would not answer further questions from the media about the test data and the interpretations it had made, but indicated it would provide that to the government inquiry, if asked.

‘‘Should the inquiry require further information about cathodic protection on the pipeline . . . then as the responsible oper- ator of that pipeline we would gladly provide that information to the inquiry,’’ he said.

The company engaged the country’s ‘‘foremost expert’’ on cathodic protection.

Northland Regional Council concluded there was ‘‘no suggestion that Refining NZ should or could have known that the incident was going to occur’’.

Justin Tighe-Umbers, executive director of the Board of Airline Representatives, which represents 29 airlines – many of which were affected by the fuel crisis – said he had not been aware of the incident earlier on the morning of the pipeline failure but said it might be neither ‘‘here nor there’’, if the damaged pipeline was a ‘‘ticking time bomb anyway’’.