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Better monitoring of tyres will mitigate serious risks

LSM Technologies’ Peter Woodford tells Jan Arreza why operators should be adopting a risk management approach to develop a documented tyre management plan.

LSM Technologies’ Peter Woodford tells Cranes and Lifting why operators should be adopting a risk management approach to develop a documented tyre management plan.

Working with off-theroad tyres for crane and earthmoving machinery can be potentially dangerous due to their large size and mass, magnitude of air or gas pressures, and the presence of combustible materials. And the uncontrolled release of this stored energy can have serious, even fatal consequences.

To avoid this, operators should be adopting a risk management approach to develop a documented tyre management plan that is current and specific, with appropriate controls to manage the many risks, according to Peter Woodford, engineering and managing director of LSM Technologies.

Pressure in a tyre is critical to its load carrying capacity and fatigue life, said Woodford, and tyre pressure monitoring systems (TPMS) are beneficial in keeping the tyre pressure within its stated pressure envelope.

“With tyre pyrolysis, when the air inside a tyre starts to gas up with a volatile form of rubber from being overheated, it will start to create excess pressure on the tyre, which can then ignite and cause an explosion,” said Woodford.

“If people really realised just how many crashes and fires have been caused through a lack of maintaining tyre pressures, it would blow their minds. Thankfully, most passenger vehicles today are automatically fitted with a TPMS, due to it being mandated around the world, just like seatbelts are,” said Woodford.

A TPMS consists of pressure and temperature sensors fitted to the tyre that communicate wirelessly with a data collection device in the operator’s cab. The operator can view the temperature and pressure of each tyre on a display in real-time, while data is continuously logged for analysis. Such systems may also incorporate alarms or alerts to warn the driver when pressure and temperature deviates from the operational range. Remote monitoring and recording may also be available.

Woodford said that a good tyre management plan clearly defines the selection, operation, maintenance and disposal of tyres, rims and wheel assemblies. The management of these items requires an integrated risk-based strategy from key departments including management, production, maintenance, supply, occupational health and safety, and the environment.

Taking a risk-based approach towards tyre management includes:

• Identifying hazards;

• Examining information on tyre and rim failures;

• Understanding the influence of the operational environment on tyre life and safety assessing and selecting tyres, wheels or rims;

• Assessing and preparing storage and work areas;

• Selecting and implementing tyre-handling facilities, including plant, tools, equipment, and safety systems of work;

• Monitoring and implementing component inspection, maintenance and repair;

• Maintaining records;

• Understanding mechanisms of tyre fires and explosions;

• Providing appropriate emergency response capability; and

• Ensuring people are competent for the tasks they are assigned.

Woodford noted that a common issue one would face has to do with tyre pyrolysis, which is the decomposition of carbonaceous material inside the tyre. Other common causes of over-temperature of tyres include:

• A combination of exceeded tyre specifications (speed/load);

• Under-pressurisation;

• Over use and/or locked brakes; and

• A combination of all of the above.

Heating of the rubber (inner liner) releases gaseous volatile organic compounds into the air chamber of the tyre and under certain temperature, pressure and concentration conditions, this volatile mix of air and fuel can become an explosive mixture and achieve auto-ignition.

Rapid spontaneous combustion typically results in large catastrophic failures with destructive outcomes. Such events can propel debris hundreds of metres and are potentially lethal to any workers in the vicinity, including people in vehicles.

Sources of heating that could result in a pyrolysis explosion, according to Woodford, include:

• Heating of stuck or ‘frozen’ wheel fasteners;

• Welding or grinding of wheel components;

• Vehicle coming into contact with high voltage electrical conductors (e.g. engine bay fires, hydraulic fires, electric fires, grass fires in parking area);

• Overheating brakes (e.g. due to brake overuse, misuse or dragging);

• Overheating of electric wheel motors;

• Gross under-inflation of tyres;

• Heat separation (i.e. separation of rubber layers in a tyre, leading to further heating from rubbing friction); and

• Overloading or over-speeding of the vehicle (e.g. exceeding its tonne kilometre per hour or load-speed rating).

Tyre pyrolysis may be mitigated by:

• Ensuring the air in the tyre does not reach auto-ignition temperature;

• Reducing the oxygen concentration in the tyre so there is insufficient oxygen to support combustion (e.g. use nitrogen for tyre inflation);

• Using a suitable liquid tyre additive;

• Monitoring the vehicle’s speed and load using on-board data acquisition and recording systems to help manage driver behaviour to stay within the TKPH rating; and

• Using a TPMS to monitor tyre pressure and temperature in real time to detect extreme air pressure or temperature anomalies.

The appropriate tyre inflation pressure settings should be determined in conjunction with the tyre manufacture for each application on site, and will depend on the tyre specifications, vehicle type and operation parameters.

Woodford said low inflation pressures can damage a tyre in a number of ways, including:

• Heat separation caused by over work;

• Irregular wear of the tread caused by excessive tread movement;

• Separation caused by excessive sidewall distortion;

• Friction and chafing caused by distortion of the bead area or slipping of the bead; and

• Separation of plies due to high stress between plies.

Such damage can cause the tyre to burst suddenly and violently, which is why pressures should be systematically recorded so that leaking or damaged tyres can be identified and changed before they fail catastrophically.

It’s for reasons like this that Woodford said TPMS is being increasingly adopted around the world. “While the systems are not mandated yet for industry vehicle tyres, they are being incorporated in many industry guidelines and standards.”

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