Water Reserve in Water Truck/ Fire Fighting Appliance
New Hope Coal Australia, West Moreton Project
The Problem
The site caterpillar 777 bulk water truck used for dust suppression at New
Hope Coal Australia’s West Moreton Project is also utilised as the main fire
fighting resource.
The 70000 litre bulk water truck is fitted with fire fighting appliances that can
be utilised for quick response to fires that may occur on site. The fire fighting
appliances include a remote control water monitor controlled from the
operators cab of the truck, low expansion foam concentrate tank available to
supply concentrate the water monitor as required, fire fighting hose reel and
auxiliary fire fighting hose outlets at the rear of the truck.
The normal sequence is for the bulk water truck to be filled with water and
utilised for dust suppression on site. The truck waters the mine roadways until
the entire bulk water tank supply is depleted and then returns to the standpipe
to refill the bulk tank. This period between when the water supply is depleted
in the bulk tank and the truck travels back to the site standpipe and refills can
be between 15 and 30 minutes dependent on the position of the water truck in
relation to the water fill standpipe.
During this period the highly efficient fire fighting appliances fitted to the bulk
water truck are rendered useless due to the lack of water on board the truck,
reducing the ability to combat fires that may eventuate on site, increasing the
risk for serious injury, loss of life or assets.
This diminished fire fighting ability was identified during a mock emergency.
An emergency call was activated and the incident controller instructed the
water truck to respond to the incident. The water truck was unable to respond
as the bulk water tank was totally depleted and the truck was on route back to
the standpipe to refill. This delayed the response to the incident by the sites
main fire fighting appliance for a considerable period of time.
The Solution
It was identified at the incident debrief that a solution needed to be found that
would maintain fire fighting capabilities with the sites primary fire fighting
appliance, the site bulk water truck.
A member of the site engineering team suggested maintaining a residual
water supply in the bulk water tank at all times that could only be used through
the fire fighting appliances. This would enable an immediate response to any
fire that eventuated on site.
This idea was recognised to have merit and plans were formalised as to how
this could be achieved.
The normal operation of the dust suppression and fire fighting systems relies
on electric over pneumatic controls. Electrical controls in the cab of the bulk
water truck activate a pneumatic control system that starts the water delivery
pump as required. Separate electrical circuits control the delivery of water to
the dust suppression sprays and the fire fighting appliances mounted on the
bulk water truck. This is a common system installed to duel purpose bulk
water trucks at most mine sites.
The goal of always having a residual supply of fire fighting water in the bulk
tank was achieved by installing a simple water level cut off switch in the bulk
water tank. The water level cut off switch that can be set at any desired level,
cuts the electrical energy supply to the dust suppression pump pneumatic
actuator in turn stopping the pump and the flow of water from the sprays. The
residual water remaining in the tank is only available to be pumped through
the fire fighting system.
The amount of residual water to remain in the bulk tank to be available solely
for fire fighting purposes was established at 10000 litres but this level could be
easily adjusted as required.
The electrical control circuit to the fire fighting pump that supplies the truck
mounted fire fighting appliances is unaffected and is the only system that can
remove the final residual water supply from the tank under normal operation.
The system does incorporate a locked override system that will allow the
residual water to be pumped through the dust suppression sprays if required
to empty the truck in the event the fire fighting system is unserviceable and
the truck is going for repair.
The electrical circuit that controls the residual water level is wired to a failsafe
mode where any faults shuts the dust suppression sprays down this prevents
undetected failure of the water level cut off switch, the fire fighting system is
still available when this mode is over ridden at the control switch.
Once the residual water system was fitted only minimal training was required
for the bulk water truck operators. The training centred on the fact that water
was always available for fire fighting and the criteria established for testing the
system each shift. The criteria for testing of the fire fighting systems mounted
on the truck at the beginning of each shift was already established the only
criteria to change was the timing of the tests from the start of shift to when the
first load of dust suppression water was depleted. This change of timing
ensured the fire fighting systems were still available by utilising the residual
water in the bulk tank that was solely for fire fighting
Benefits
The period where the highly efficient fire fighting appliances fitted to the bulk
water truck are rendered useless due to the lack of water on board the truck,
reducing the ability to combat fires that may eventuate on site, increasing the
risk for serious injury, loss of life or assets has been eliminated with the
introduction of the residual water system fitted to the mine site bulk water
truck.
The residual water supply in the bulk water truck allows this piece of
equipment to remain productive and efficient in the normal mining cycle but
also provide valuable insurance in being prepared to combat fires that may
eventuate.
The bulk water trucks residual water supply provides the site a greater
confidence in being able to respond in a timely manor to an emergency
involving a fire. The water truck operator never has to make the painful reply
“I’m on my way back to fill up can not respond” in response to a call to assist
in a fire situation.
The components for the entire system cost approximately 70 dollars and take
approximately 3 hours to install.
The residual water system is a low cost innovation that is very simple in
operation an easily installed which provides an extremely cost effective
insurance policy when considering the potential consequences of loss of life
or assets valued at millions of dollars.
The major component of the system which is the water level cut off switch is
low cost allowing a spare switch to be kept as a stock item in the store system
Transferability across Industry
The residual water system can be installed and utilised at any site where the
bulk water truck is a duel purpose appliance of dust suppression and
emergency fire fighting appliance.
The system could also be adapted to fixed installations where a residual fire
fighting water capacity is required on general use water reservoirs in such
area as coal preparation plants and mills etc
The components utilised to install the system are all off the shelf items and
are readily available. The installation is quick and only requires basic
mechanical and low voltage electrical skills.
The quantity of residual water remaining in the tank can be easily adjusted if
required in a short period of time.
Plan of Residual Water System