Cradle-Mounted Fire Suppression Cylinder
A cradle-mounted vehicle fire suppression cylinder plumbed to a side unit, showing a damaged hose, no discharge when needed, an unintended discharge and a cylinder that comes loose.
In service. Mounted in its cradle, connected and armed as the system's documentation requires. Nothing happens until the system is triggered — by its detection or by hand, whichever this system uses.
Deviation library
Components
Explore the equipment
Hold an extinguishing agent ready to discharge through fixed pipework onto a fire in a vehicle's engine bay or another protected space when the system is triggered. This is a cylinder strapped into a cradle, with a hose running from the centre fitting on one end to a ribbed unit mounted alongside it, and a block fitting on the opposite end. It is vehicle equipment, not process plant, and carries no tags. The model does not identify the side unit's function — on suppression systems a unit plumbed like this can be part of the release or of the fire detection — and it shows no pressure gauge. Nor does it show the detection, the distribution pipework or the nozzles, or tell you the agent, whether it is stored under pressure, or its service and test dates. Read those from the system's documentation and its service record before working any case here.
Components
Cylinder
The pressure vessel that holds the agent. Whether it holds its pressure all the time or is pressurised at release is not shown, so it is treated as pressurised whenever it is charged.
Normally: Charged, undented, free of corrosion and within its test date.
End fittings
The centre fitting on one end, where the hose connects, and the block fitting on the other end. Which of them is the agent outlet the model does not say; both are fittings on a charged cylinder.
Normally: Tight and leak-free, with nothing loosened while the cylinder is charged.
Hose
The flexible hose connecting the centre fitting on the cylinder's end to the side unit.
Normally: Unkinked, undamaged and secured at both ends, routed clear of heat and moving parts.
Side-mounted unit
The ribbed unit mounted alongside the cylinder and connected to it by the hose, with a port at its far end. The model does not identify its function, so it is named for where it sits; confirm what it is from the system's documentation before relying on it.
Normally: Secure on the cradle, undamaged, with its hose and port connections made.
Cradle and straps
The cradle the cylinder and the side unit sit in, the straps and clamps that hold the cylinder in it, and the fixings to the vehicle.
Normally: Tight, uncorroded and holding both units without movement.
Operating states
Being fitted or serviced
The release is made safe by the manufacturer's method before anything is touched, the cylinder is lifted by its body, and no fitting is loosened while it is charged. The hose and the side unit stay connected unless the procedure says otherwise.
In service
Mounted in its cradle, connected and armed as the system's documentation requires. Nothing happens until the system is triggered — by its detection or by hand, whichever this system uses.
Released
The system is triggered, the cylinder discharges through its pipework to the nozzles, and the operator stops, switches off and gets out.
After a discharge
The protected space is ventilated and left until clear, clean-up follows the agent's safety data sheet, and the vehicle stays out of service until the system has been recharged or replaced and the cause found.
Failure scenarios and safeguards
OTHER THANHose integrity
The damage is found at an inspection and the hose replaced before the vehicle is used.
Causes
- Hose chafed against the vehicle or the cradle
- Hose heat-damaged by a nearby exhaust or turbocharger
- Fitting loosened during other work and not retightened
How it develops
- 01The hose is damaged or comes loose at one end.
- 02The connection between the cylinder and the side unit is lost, and the system cannot be relied on to work as designed.
Safeguards
Hose and connection checks
The hose and its connections at the cylinder and the side unit are checked during pre-use and service inspections for chafing, heat damage, kinks and loose fittings.
If it fails: A damaged or disconnected hose goes unnoticed until the system is needed.
Inspection and service by a competent person
The cylinder, its valve, its release and its pipework are inspected and serviced at the interval the manufacturer and local rules require: pressure or contents checked, the cylinder examined for damage and corrosion, test dates confirmed, and the release proved.
If it fails: The system's condition is unknown until the day it is needed.
Unmitigated: A system that looks complete and does not work when a fire starts.
NODischarge
A serviced, armed system discharges when released; and an operator who knows the system is only a delay is already getting out.
Causes
- Release left in its safe position after maintenance
- Release cable or actuator disconnected, seized or damaged
- Cylinder empty or below its working pressure after a slow leak or an unrecorded discharge
- Distribution pipework disconnected, crushed or blocked
How it develops
- 01A fire starts and the system is triggered.
- 02The valve does not open, or it opens on a cylinder with too little left in it to discharge.
- 03No agent reaches the fire, and the fire grows while the operator waits for the system to work.
Safeguards
Inspection and service by a competent person
The cylinder, its valve, its release and its pipework are inspected and serviced at the interval the manufacturer and local rules require: pressure or contents checked, the cylinder examined for damage and corrosion, test dates confirmed, and the release proved.
If it fails: The system's condition is unknown until the day it is needed.
Release made safe for handling and maintenance
Before the cylinder is handled, removed or worked near, its release is made safe by the manufacturer's method — the safety pin in, the actuator disconnected — and nobody loosens the valve or its fittings on a pressurised cylinder. It is re-armed, and the arming checked, before the vehicle returns to service.
If it fails: A release knocked during work discharges the system, or a valve loosened under pressure lets go.
Pipework and nozzle checks
The distribution pipework and nozzles — not in the model — are checked as part of the service: connected, undamaged, routed clear of heat and moving parts, and with any nozzle caps in place so the outlets are not blocked by dirt.
If it fails: The agent leaves the cylinder and never reaches the fire.
Operator briefed on the release and the response
Whoever drives or operates the vehicle knows where the release is, when to use it, and what follows: stop, switch off, get out and away, and raise the alarm. The system buys time to escape; it is not a reason to stay.
If it fails: The release is not used, or is used and the operator stays with the vehicle.
Unmitigated: The fire develops unopposed in the engine bay or the protected space, with the operator still inside the vehicle relying on a system that did not work.
OTHER THANRelease
With the release made safe for the work, nothing discharges; if it does, the space is ventilated and left until it is clear.
Causes
- Release knocked or pulled while working near it, with the safety removed
- Cylinder dropped or struck while being handled armed
- Release cable snagged or tensioned by something else on the vehicle
How it develops
- 01The system is triggered with nobody expecting it.
- 02The cylinder discharges through its valve — into the protected space, or, if the pipework is off, straight out of the valve.
- 03A loose or unmounted cylinder discharging from an open outlet is driven by its own release and can move violently.
Safeguards
Release made safe for handling and maintenance
Before the cylinder is handled, removed or worked near, its release is made safe by the manufacturer's method — the safety pin in, the actuator disconnected — and nobody loosens the valve or its fittings on a pressurised cylinder. It is re-armed, and the arming checked, before the vehicle returns to service.
If it fails: A release knocked during work discharges the system, or a valve loosened under pressure lets go.
Secure mounting
The cylinder sits in the brackets and straps its manufacturer specifies, fixed to structure that can hold it under braking and in a collision, with the straps tight and nothing corroded or cracked.
If it fails: The cylinder works loose, chafes, or comes free in a collision.
Response after any discharge
After a discharge the space it went into is ventilated and left until it is clear, the agent's safety data sheet is followed for clean-up and exposure, and the vehicle stays out of service until the system has been recharged or replaced and the cause found.
If it fails: People breathe or handle the agent, or the vehicle goes back into service with an empty cylinder.
Unmitigated: Agent released into an occupied cab or a workshop, a startled person injured by a moving cylinder, and a vehicle with an empty system that nobody knows about.
OTHER THANMounting
Tight, sound mounting holds the cylinder where it was fitted through vibration and impact.
Causes
- Straps or brackets loose, corroded or cracked
- Cylinder refitted without its full set of fixings
- Mounting structure not strong enough for the cylinder in a collision
How it develops
- 01The cylinder is no longer held firmly; it shifts with vibration and chafes against its straps.
- 02In heavy braking or a collision it comes free, and the valve head — the weakest part of a pressurised cylinder — takes the blow.
Safeguards
Secure mounting
The cylinder sits in the brackets and straps its manufacturer specifies, fixed to structure that can hold it under braking and in a collision, with the straps tight and nothing corroded or cracked.
If it fails: The cylinder works loose, chafes, or comes free in a collision.
Inspection and service by a competent person
The cylinder, its valve, its release and its pipework are inspected and serviced at the interval the manufacturer and local rules require: pressure or contents checked, the cylinder examined for damage and corrosion, test dates confirmed, and the release proved.
If it fails: The system's condition is unknown until the day it is needed.
Unmitigated: A heavy cylinder loose in the vehicle in a crash, and a damaged valve on a pressurised cylinder that can release violently.
