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Mining, fluid power, MDG-41 and hose safety

Fluid injection injuries can be lethal and therefore fluid power systems, and those who work with them, should be treated with the seriousness they deserve, Neil Martin reports.

In a mining environment, both aboveground and underground, there is a high level of exposure to fluid power related equipment and machinery. This includes various hydraulic components of high pressure storage such as complex accumulators and simple connection methods such as in hydraulic hoses. Hydraulic hoses are the means through which hydraulic fluid is transmitted throughout the machine. The high majority of these hoses are subjected to high pressure which can be latent without any indication of stored energy.

An increasing percentage of fluid injection injuries and fatalities in recent times on work sites were all about the dangers of stored fluid energy showing that hydraulic pressure is often being misunderstood by maintenance personnel. These incidences relate to fluid injection and severe body injuries from contact with fluid under pressure. High pressure stored energy of fluid or oil in hydraulic systems is lethal if a fluid line connection point is opened or hose failure occurs.

The death of a 27-year-old man in a fluid power related workplace accident at an iron ore mine in Western Australia in August 2011 has thrust fluid power safety back into the spotlight in Australia. The man was killed while changing a hydraulic cylinder on a front-end loader.

Internationally, hydraulic system safety is also being stressed after a 41-year-old man was killed when a hydraulic jack mounted on a longwall shield in the US state of Ohio catastrophically failed.

In the last four financial years there have been 161 fluid injection injury claims lodged in the NSW coal industry alone. This figure is nearly three times higher than the number of electric shock claims lodged.

Fluid injection claims which were lodged included:

  • He was attempting to disconnect hoses off the Quick Detachment System (QDS) on an underground mining loader when the hydraulic hoses released under pressure striking him in the chest and covering him in hydraulic fluid resulting in a suspected fluid injection.
  • Worker was removing a hydraulic oil hose that still had pressure in it causing oil to spray onto his lower arm.
  • Miner was disconnecting hoses off a QDS after pressing pressure release and the miner was sprayed with oil resulting in possible fluid injection.

In the past decade, the fluid power industry has experienced a high level of change with the fast progression of technology and modern applications. The risk of fluid injection injury is increasing as machinery and equipment with high pressure hydraulic and lubrication systems becomes more common; more functions are being automated on machines, tighter hose compartment designs, reduced weight for fuel efficiencies, programmed maintenance and hose wrapping/shielding requirements. These factors increase the risk for maintenance personnel carrying out regular tasks on the machine’s hydraulic systems.

Due to the number of fluid injection injuries occurring from the use of pressurised fluid power systems, in 2010 the NSW Department of Industry and Investment introduced draft guidelines for fluid power system safety at mines, otherwise known as Mechanical Design Guideline 41 (MDG-41).

The purpose and scope of MDG-41 is to manage risks associated with hydraulic/fluid power systems. It applies to longwalls, mobile plant, mining and construction related machines, open cut and underground sites, development equipment, fixed installations, compressed air systems and more. It covers new and second hand equipment (operated/ maintained/overhauled) and includes all applications greater than 5Mpa or 60 degrees Celsius.

MDG-41 is a guideline covering the hazard identification, assessment, elimination and reviewing of risk. This includes properly instructed, trained and competent personnel.

The guideline covers seven main areas relating to fluid power these being; standards for, and maintenance of, fluid power systems including occupational health and safety and emergency preparedness; design, manufacture and installation of fluid power systems; safe work procedures for site installation; site commissioning; site operation including operational procedures and defects; inspection, maintenance and repair including audits; and decommissioning.

MDG-41 contains specifications relating to hose management and the development of a hose maintenance program. The guideline states that the implementation of a hose management program “will reduce equipment downtime, maintain peak operating performance, and reduce the risk for personal injury and/or property damage”. It recommends that a hose management program should include a database of hose assemblies on site, a maintenance schedule, testing and certification procedures, labelling guidelines, and hose failure analysis.

Hose failure inspections are also covered in the guideline including periodic inspection schedules, in-service inspections, hose discard criteria, hose storage, and hose maintenance. The hose maintenance recommendations state that “hydraulic hoses and components have a finite life, and at some stage the hose assembly should be replaced irrespective of the visual condition”. MDG-41 recommends that hoses should not be in service for a period longer than eight years.

The guideline states that hydraulic hose shall comply with the provisions of ISO 6805 or SAE J517 and should meet a range of criteria including; being rated appropriately for system pressures; selected to meet fluid and ambient temperatures; being able to withstand environmental conditions including abrasion and corrosion; and, meeting fire resistance requirements.

Hoses, hose ends, hose assemblies and adaptors should be labelled as recommended in the guidelines including; manufacturer’s mark and name; class/type of hose, date of manufacture; description; batch code; maximum working pressure; and part number.

The MDG-41 guidelines also establish safe working practices for the manufacture and assembly of high pressure hose and fittings for such manufacturers as Parker Hannifin, Alfa Gomma and hose fitting services provided by such companies as ENZED and Pirtek. These practices include; material supply verification, quality planning and testing, competent staff for fabrication, cleaning and packaging, and testing and certification.

MDG-41 has now been finalised and has been formally accepted and supported by The Department of Mines and Energy QLD and The Department of Mines and Petroleum WA. It is anticipated that this guideline will ultimately become a national standard for safety with working with fluid power in a mining environment.

Along with these guidelines, industry incorporates available technology to lower the risk of working with fluid power. Providing maintenance personnel with information regarding the pressure in hydraulic hoses helps to lower the risks involved.

In terms of testing hydraulic pressure there are several devices on the market including hydraulic deadweight pressure testers, access check points and hydraulic pressure transducer, data monitoring equipment and gauges. These devices are invasive requiring connections to fluid lines such as valves, probes and other such means. Installing these devices is in itself a risk to personal safety due to a risk of potential exposure to fluid under pressure.

The electrical industry has preventative safety devices, such as the non-invasive tool Ezi-scan, available to them. This hand held device was developed as a method to non-invasively detect if there is any electrical activity in the area of work to be performed. Called ‘the last line of defence’, the Ezi-scan type device is now standard issue to trained electrical personnel and is a significant contributor to the electrical shock reductions in the electrical industry. However, the fluid power industry currently has no non-invasive means of detecting whether a hydraulic hose/system is under pressure.

With the support of a grant from the Australian Coal Association Research Program (ACARP), Custom Fluidpower has developed a prototype of a non-invasive pressure detection device (PDD) for hydraulic hoses. This device (patent pending) can inform an operator if there is pressure in a hydraulic hose. This hand held device is simple in operation and can detect stored energy/pressure in hydraulic hoses from pilot size of ¼” (6mm) to full system operation up to 2” (50mm) regardless of the manufacturer, lining, braiding and cover.

The commercialisation process for the nonintrinsically safe surface use version of this device is well underway. Once manufactured, the PDD will provide the last line of defence against high pressure fluid injection injury. Custom Fluidpower envisages that the use of the PDD will be incorporated into current mine safety guidelines and procedures for safe operating procedures. Custom Fluidpower has interest in developing this device to the next level of a full intrinsically safe version suitable for underground use.

In conjunction with the MDG-41 Guidelines and safety technology, training has a large role to play in improving safety when working with fluid power systems and hoses under pressure.

As trade trainees, field maintenance trainees and engineers move through their trade courses and studies there is very little content when it comes to fluid power within these apprenticeships and courses. Unless the individual has an interest in this specific field and works directly within the fluid power industry and completes extra courses to be a specialist in fluid power their understanding of dangers in stored energy is limited.

With the potential safety risks involved, the fluid power industry should command the same level of training available to other trade industries such as electrical.

The rapid technology changes within industry have resulted in difficulties for traditional fluid power training organisations in staying current regarding industry practices, component knowledge and qualified resources. Stored energy risks are not just found on sites with mining type equipment. It is evident in maintenance and repair workshops, equipment and part sales, and all facets of industry using fluid power related equipment. It is a bomb just waiting to be detonated.

Fluid injection injuries can be lethal and therefore fluid power systems, and those who work with them, should be treated with the seriousness they deserve. Adherence to MDG-41 guidelines, the uptake of safety technology, and quality training are all factors which will lower the safety risks of working with fluid under pressure in hoses in a mining environment. Taking fluid power and stored energy seriously will save lives. Our goal is zero harm – if it’s not safe, make it safe.

Neil Martin

Sales Director Custom Fluidpower

Neil started his career in the fluid power industry as an apprentice fitter and turner in 1975. In 1979 he joined Lucas Fluid Power and spent 11 years there, reaching State Manager level at the age of 27. Further education has been part of Neil’s growth, completing courses in Mechanical Engineering and Advanced Fluid Power. During 1991 Neil moved to Simon Hydraulics, now Custom Fluidpower, in Brisbane and began reforming the sales team. Neil was appointed to the position of National Sales Manager in 2004 and September 2006 he was appointed to the board as Sales Director.

Company Profile

Custom Fluidpower is a wholly Australian owned company offering hydraulic, pneumatic, filtration and lubrication product sales along with complete system design, installation and commissioning, and service and repairs. Custom Fluidpower services the agricultural, aerospace, exploration, industrial, marine, mobile, mining and material handling industries Australia wide. For further information call 1300 781 178 or visit www.custom.com.au for more information.

Custom Fluid Power Training is a Registered Training Organisation providing fluid power training based on current industry practices. They provide services Australia wide and can customise training courses for your organisation. For further information call (07) 3307 8243 or visit www.cfpt.com.au for more information.

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