Near Mishap for Collins Sub, HMAS Sheean.

HMAS Sheean at Pearl Harbour, USA, 2014. (Photo courtesy US Navy via Wikipedia)
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Andrew Tillett for the Australian Financial Review (AFR) reported May 7, 2022:

"One of Australia’s ageing Collins class submarines flooded as it was about to embark on a deep dive, sparking fears among crew it could sink during drills off the West Australian coast last year. 

Quick thinking by HMAS Sheean’s crew averted disaster, with the submarine conducting an emergency surfacing after a back-up system designed to stop water flooding into the boat initially failed to work.

The incident has raised concerns about a lax safety culture on board, according to navy insiders, with some of the traumatised crew transferring off the boat.

The Defence Department confirmed there was a “minor flooding incident” on the submarine but denied it could have sunk.

“In accordance with standard procedures, HMAS Sheean surfaced immediately and self-propelled back to base. There was no risk of the submarine sinking and HMAS Sheean was returned to service within days,” a Defence statement said.

“Safety is the Submarine Force’s number one priority and this is well communicated at every level. The physical and mental health of our people is paramount and there are support systems in place to address any issues in the short and long term.”

HMAS Sheean, which entered service in 2001, sailed from Perth’s submarine base on September 21 last year to the West Australian exercise area to complete its operational work-up – the safety checks and other tasks before the submarine goes on patrol.

At 9.43pm that night, “an uncontrolled ingress of water” was reported in the motor room on the forward auxiliary seawater pump, according to a Defence Department investigation report seen by AFR Weekend.

The pump brings water into the submarine as part of its cooling system, although it has been described as a non-critical component.

The incident was initially reported as a fire after water vapour triggered a fire alarm, but the crew saw there was no smoke and started its emergency flood plan.

While the submarine surfaced within three minutes of the first alarm, the response was “complicated” after an automatic system meant to stop water flowing into the submarine during a flood failed to work.

The “shut all hull valves” system had been isolated from the main electrical system earlier that day as technicians tried to fix an electrical issue. The valves were meant to be shut but should have been checked before diving, a source said.

Because the system was isolated, it was unable to be activated automatically, although it appears in this case it was overridden locally.

The accident happened 10 metres above the submarine’s deep-diving depth. The Collins class’ exact deep-diving depth is classified, although they can dive more than 180 metres under the water.

It is unclear how much water entered the submarine but a Collins class submarine can take on no more than 15 tonnes before it starts to sink.

When HMAS Dechaineux flooded in 2003 [see an April 2021 SubMatt’s reference to that]  to that mishap] after a pipe burst, it came within 20 seconds of sinking after about 12 tonnes of water entered the boat.

The report said a single open-ended flood through the auxiliary seawater pipework with a 111 millimetre diameter was the “worst possible outcome” and at the depth HMAS Sheean was operating, water would have poured into the boat at a rate of four tonnes per second.

A source familiar with the event said the pipe that broke in HMAS Sheean was smaller than this diameter but if “the flood had occurred on a larger pipe we would have lost Sheean and all personnel on board as it occurred at deep-diving depth”.

They said some crew had transferred off the submarine because of the psychological trauma.

Another source said it was highly unusual that the emergency valve shut off would be isolated at diving depth.

Former navy commodore and Collins class project director Paul Greenfield said “these sorts of occurrences are rare” but the rapid rate the submarine surfaced suggested it was serious.

“The training is such that submariners know exactly what to do if it does occur,” he said.

Another Collins class submarine, HMAS Waller, flooded twice last year in a matter of weeks before a major electrical fire onboard." [see an August 2021 SubMatt’s article on that].