An after-market extension tube fitted to an exhaust manifold gas sampling point had failed as the vehicle was being driven along a main underground transport road.
The operator witnessed sparks coming from under the dash before realising that a copper pipe used to gather raw gas samples from the exhaust manifold test point had failed.
While the cause is uncertain, the sparks were most likely from hot carbon particles in the raw exhaust of the diesel engine system which glowed as they became oxygenated in the atmosphere.
Subsequently, a number of other diesel engine systems were also found to be operating with copper sample pipes from the raw exhaust manifold test point to a convenient location within the engine compartment.
“Any extension to the gas test point connection at the exhaust manifold is subject to significant vibration, potential inadvertent damage, fatigue and/or heat affected failure. Copper pipe may become brittle and be subject to fatigue cracking in situations of frequent vibration and/or excessive heat,” NSW Mine Safety Operations Branch director Rob Regan said.
The extensions to the gas test point were not covered by the detailed registration documents for the diesel engine systems.
The engine system as tested for registration did not include a gas sample point extension line.
“All mines and owners of diesel engine systems should check their diesel engine raw exhaust gas points for unauthorised alteration, such as copper pipe extensions, wrong fittings and exhaust flametraps in lieu of caps,” Regan said.
“If found, immediately remove all extension pipes to the gas sample point and plug the test point with an appropriate fitting, where this has not been accessed as part of the design registration for the diesel engine system.
“If remote sample points are required for raw gas testing, then use an appropriately purpose built sample line and immediately after testing is complete, remove the sample line and block off the sample point back at the exhaust manifold with the appropriate fitting.”