Moomba
plant update
Posted: 5 March 2004
Santos Limited advises that investigations into the cause of the
1 January 2004 fire at the Moomba Gas Plant are continuing.
As previously reported, the cause of the gas release that led to
the fire was the unforeseen failure of a heat exchanger (cold box)
inlet nozzle in the Liquids Recovery Plant (LRP) - the final stage
of liquids processing in the plant.
Findings from an initial independent metallurgical laboratory study
— commissioned by Santos and based on analysis of samples
taken from the affected area — have now confirmed that the
unforeseen failure of the inlet nozzle was due to Liquid Metal Embrittlement
(LME) of the train B aluminium cold box by elemental mercury.
Further investigations being undertaken by Santos involve additional
assessment of the cold box, to determine if any other factors may
have contributed to the incident. These investigations are expected
to take some weeks to be completed.
LME is a rare instantaneous phenomenon. It is a complex metal fracture
mechanism that occurs without warning. It is understood that, to
date, the Moomba incident is the first known occurrence of a gas
release and fire due to LME.
While LME occurs with aluminium, it does not occur with steel and
therefore does not affect the strength of steel pipes and valves.
At the Moomba Plant, the cold box is the only major piece of aluminium
equipment.
The remainder of the processing equipment is predominantly constructed
of steel. Natural gas from subterranean reservoirs in Australia
and South East Asia typically contains minute levels of elemental
mercury. Central Australian raw natural gas contains approximately
30 parts per billion of elemental mercury.
Santos has in place a management plan for dealing with elemental
mercury in the Plant, including susceptible aluminium components.
This plan reflects accepted industry practice.
Notwithstanding that the investigation process has not yet been
completed, Santos has already taken the decision to implement a
re-instatement plan to eliminate the possibility of a similar failure
occurring again. This plan includes the procurement of new cold
boxes and associated facilities.
Santos maintains insurance which covers it for damage by fire.
Santos’ insurers (as well as the Government) are aware of
LME and the issue of elemental mercury in relation to that failure
mechanism. The insurance claim is being progressed in the normal
fashion.
As detailed in the Santos release of 23 February, the Moomba Plant
is on track for restoration of full production. As well as currently
meeting full market demand, surplus production gas is also being
injected into underground storage to replenish reserves.
For more information see www.santos.com
Posted by Richard Price,
Editor Pipeline Magazine
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