Preventing mobile plant fires

Background

Since January 2010, there has been 23 incidents involving fire on mobile plant at mines in Victoria - 19 occurred in underground mines and four in open cut mines.

Typical causes of fire include component failure and/or inadequate maintenance.

Identified causes

The common contributing factors were failure to maintain:

• integrity of pressurised hydraulic hoses
• hydraulic lines clear of heated surfaces (inadequate clearance or insulation)
• sources of oil leaking onto hot engine components
• hose type, transmission coolers and power train components to manufacturer’s requirements
• brake fluid lines from overheated brake friction material issues
• hydraulic, mechanical and electrical components on a regular basis
• tyres to manufacturer’s requirements
• build-up of material between hoses and heated surfaces, hence allowing thermal conduction and ignition
• frayed electrical connections

Other factors included failure to:

• respond to overheating issues with engine turbochargers
• exactly locate and determine the source of the original reported fire that occurred hours earlier on the plant
• reset/recalibrate auto-fire suppression system immediately after initial activation.

Preventative control measures

Design

• Ensure hydraulic components are ‘like for like’ and considered suitable for use. Always consult plant manufacturer before making changes.
• Ensure any contractor installations/design modifications that are undertaken off-site are verified on-site by the employer before use and are equivalent to manufacturer’s standards and design.
• Implement quality checks by manufacturer-authorised service providers periodically as a cross check for internal maintenance.
• Evaluate potential alternative higher flash point manufacturer-approved hydraulic oils, which contain Polyol Ester based fluids, phosphate esters or water glycol and emulsions. Such fluids must be compatible to the existing in situ components such as seals/fittings.

Installation

• Properly fit any attached or in situ hoses with approved manufacturer components.
• Maintain hydraulic equipment with the appropriate fit-for-purpose tools.
• Routinely check hose clamp type.
• Use fire resistant anti-static hoses whenever possible and consider high temperature tolerant hoses designed for oil operating temperatures >150 ºC.
• Install and evaluate insulation around hot components or insulate hoses near hot components and upgrade to braided armour type hoses.
• Ensure wiring is protected against fire, and connections are appropriate to manufacturer’s requirements and suitably located.
• Consider the location and rating of protective devices such as fuses, solenoids and non-return valves.

Inspection and maintenance

• Complete pre-start checks for locating and acting on oil leaks, sprays and stains.
• Ensure the maintenance work order system includes the correct selection integrity and testing of control measures.
• Use thermal imaging equipment to detect hot spots and high temperature areas of plant during maintenance programs.
• Ensure high current wiring is not in close contact with hydraulic hoses.
• Routinely wash, clean and check hoses for any sources of rubbing, oily mist or leaks.
• Carry out periodic checks on hydraulic braking systems to ensure sound operation, including bearings brake drums, rotor and callipers.
• Routinely check electrical wiring including insulation.
• Routinely check solenoid connections for corrosion and replace/check at set engine hours or as per manufacturer recommendations. Consider protective devices for solenoids such as fuses.

Emergency response

• Install fire detection and automatic fire suppression on plant that is used in high risk zones and install engine auto-shutdown systems that operate when the fire suppression system is discharged.
• Ensure communication of fire-related events, maintenance incidents and subsequent attendance and associated follow-up is clear to employees.

More information

• Australian Standard 5062–2006 - Fire protection for mobile and transportable equipment (it has useful and practical information on fire management including: fire types, ignition sources, potential fire hazard locations, and fire analysis and fire protection systems).
• ASTM E659 78 (2005) - Standard test method for auto ignition temperature of liquid chemicals.