Guideline raises the bar

The injuries typically occur when hydraulic fluid escapes under pressure from a “pin prick” hole in a failed hydraulic hose. The jet of fluid pierces the skin and flesh as easily as a jabbed hypodermic needle.Oil injection can cause permanent muscle and tissue damage, or worse. According to the New South Wales Department of Primary Industry, there have been two fatalities from injection of high-pressure hydraulics in the state in the past 20 years. Both deaths occurred in longwall coalmines. Modern, high-pressure hydraulics can cause injury anywhere, but the longwall, with its combination of miners working closely alongside thousands of high-pressure hoses in a hot, dusty, corrosive environment, is a particularly – probably uniquely – dangerous place. An analysis of United States and Australian plant and equipment-related mining injuries published by the DPI in 2007 showed 255 longwall hydraulic incidents over an eight-year span. More than 60% of those incidents were caused by hose or fitting failure, and three quarters of those were “walk-bys” – that is, they did not happen during scheduled maintenance but involved a miner who was unlucky enough to be close by when the hydraulic assembly failed.“This was not a sustainable situation and required a cultural change within the industry when dealing with this technology,” a NSW DPI spokesperson said.Hence, the NSW DPI came up with the MDG 41 Guideline for Fluid Power System Safety at Mines. It began as a plan to boost safety at underground coal mining longwalls but its influence is spreading to other areas, including mobile mining and construction equipment. MDG 41 is NSW DPI’s framework to bring about that change. “MDG 41’s inception was the result of a safety vacuum which existed with regard to high-pressure hydraulics as applied to mining equipment,” the spokesperson said.Development of the guideline began in 2004 and involved equipment manufacturers, the mining industry, hose and fitting suppliers and installers, unions and NSW DPI Mine Safety Operations branch inspectors. The NSW DPI spokesperson said that while MDG 41 was and is government driven, “recognition of the contribution and commitment to the document by parties other than government must be made as it has been significant”.MDG 41 was released as a prepublication draft in August, with its 85 pages covering every aspect of hydraulics, from design to testing, installation, training and injury treatment procedures. NSW DPI said the draft had been reviewed by industry stakeholders and final revisions were considered at a recent industry working party meeting with a view to final publication this month.The dangers of hydraulic fluid escaping at high pressure are not limited to longwalls. In one recent incident at a NSW mine, a wheel loader operator was injured when the hydraulic hose controlling his loader’s bucket tilt function burst. The energy contained in the resulting jet of pressurised fluid was enough to smash the windscreen of the wheel loader.At least one manufacturer of excavators, wheel loaders and dump trucks has been looking closely at promoting its hydraulic systems and maintenance as MDG 41-compliant.The hose replacement industry has certainly embraced MDG 41, with a number of prominent suppliers marketing their products and procedures as complying with the guideline’s requirements.MDG 41’s prescriptive approach hasn’t met with universal approval from hose and fitting suppliers, particularly regarding the requirement that “hose assemblies shall only be carried out using ‘matched’ hoses and fittings”. MDG 41 defines a matched system as “where the hose and fittings (insert/ferrule) are from the same manufacturer and are assembled and crimped using the method as specified by that manufacturer”.One supplier said that although its hoses and fittings were sourced from separate manufacturers, those manufacturers had been chosen because their products exceeded tough international standards – the same standards that applied to the matched systems approved by MDG 41.Another supplier suggested the tough testing and certification regimes specified in MDG 41 may be too expensive to implement – a concern shared by some mine operators.

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