Large quantities of hydraulic oil and fuel next to very hot surfaces in an enclosed engine bay.

Turbochargers, exhausts and brakes all reach temperatures well above the ignition point of hydraulic oil.

A hose failure spraying oil onto a hot surface is the classic sequence.

The resulting fire destroys a machine worth a great deal in minutes.

Machines often operate far from help and are frequently unattended when a fire starts.

Mining, forestry, agriculture, waste handling and heavy construction are the main sectors.

Because a fire could start anywhere in the engine bay, and point detectors would be shaken loose or coated in dust.

A heat-sensitive tube or wire is routed through the risk areas.

It detects fire anywhere along its length rather than at fixed points.

Pneumatic tube systems both detect and actuate, which removes the need for electrical power.

Routing is a design decision based on where fires actually start on that machine type.

The tubing is inspected for damage and chafing at every service.

Because knockdown alone is insufficient on a machine whose exhaust manifold is still glowing.

Dry chemical knocks flame down rapidly.

A liquid agent cools hot surfaces and prevents reignition.

Using both addresses the two halves of the problem in sequence.

Single-agent systems exist and suit lower-temperature hazards.

Agent selection is matched to the machine type and its known fire history.

They are the leading causes of faults found at service, and components are designed around them.

Continuous shock loading loosens fittings and fatigues brackets.

Nozzles carry caps against dust and high-pressure washing.

Pipework routing and clamping prevents chafing, which is a frequent finding.

Temperature extremes affect agent condition and cylinder pressure.

Regular inspection is more important here than on any fixed installation.

Both in the cab and at ground level, so the operator can trigger it while escaping and someone outside can trigger it for an unattended machine.

An operator's first action is usually to get out of the machine.

A ground-level station lets anyone nearby act on an unattended fire.

Stations must be reachable without approaching the fire.

They are marked clearly and kept free of the mud and dust that machines accumulate.

Automatic actuation operates regardless, which matters for a machine parked and unattended.

Shut down the engine and isolate fuel, because a running engine keeps pumping fuel and oil into the fire.

Engine shutdown removes the pressure driving a hydraulic or fuel leak.

It also stops the cooling fan spreading flame through the engine bay.

Battery isolation is often included to remove electrical ignition sources.

Interlocks are tested at service rather than assumed.

Some operators require a delay so the machine can be brought to a safe stop first.

Frequent inspection by comparison with fixed systems - the environment is far harsher.

Detection tubing is checked for damage, chafing and correct routing.

Nozzle caps are replaced and nozzles checked for blockage.

Agent quantity and cylinder pressure are verified.

Actuation stations and interlocks are functionally tested.

Intervals are set by the manufacturer and the local regime, and are typically shorter than for fixed installations.