Pump up the volume
Published: 01 July, 2007
Increasingly, more incidents are occurring where an existing fixed water supply system has been rendered useless. An initial explosion on a site has wiped out the fixed system completely.
In other incidents the fixed system might not have been able to provide the quantity of water required to combat the situation. When this is the case, there is no other alternative but to get water from an open source like a canal, river, lake or even open sea.
But, not having the right equipment may still leave you helpless if you cannot get to the water to get the water.
Not every pump sucks!
Conventional pumping systems are drafting pumps. These pumps will have to be placed close to the water’s edge to enable them to draft water though hard suctions hoses. For large capacity pumping units this may require up to 8 to 10 parallel suction hoses, a laborious and time-consuming job. Then the hose will need to be primed, further complicating matters.
The problem with drafting pumps is that there is a limit to how far the water can be drafted. There is a limit about how long the suction hoses can be and from what depth the water can be drafted from.
Most importantly is the drafting height; it becomes nearly impossible to draft water from an open source if the drafting height exceeds 7.5 metres. And there is a price to be paid - draft water from these depths and the output capacity of the pump may only be 20-30% of its rated capacity.
For example, a drafting pump with a rated capacity of 3,000 lpm at a 3-metre drafting height will only deliver 1,000 lpm when drafted from 5 to7 metres.
So, although these pumps have been the industry standard for many years, they are not the solution to the increased demand in getting to the open water. However, there is a solution, a pumping system whereby the drafting problem and access to open water is no longer an issue.
HydroSubs from The Netherlands
To eliminate the drafting problems would actually mean placing the pump in the water. Many firefighting vehicles cannot achieve this, so the trick is to place a system inbetween the prime power source, the diesel engine, and the water pump.
This system should generate enough distance between the diesel engine and the water pump to enable the water pump to be placed into the water while the primer mover is on shore.
This can be achieved by using hydraulics. A well-designed hydraulic system can transfer power over relatively long distances efficiently through high pressure hydraulic lines.
When putting this system together, it is easy to see that the hydraulic pump can be coupled directly to the diesel engine and the hydraulic motor is coupled directly to the water pump, inbetween there is the hydraulic pressure hose.
The hydraulic motor and water pump are placed in a lightweight stainless steel frame with a floating device; the hydraulic driven submersible pump. The standard length of the hydraulic hose is 60 metres (180ft) and this is the maximum distance over which an open water source can be reached.
This distance can be horizontally or even vertically, for example; it is possible to get the pump in the water from a bridge and still be able to pump the water 60 metres up on top of the bridge.
The HydroSub basically eliminates all access problems involving open water. The lightweight submersible pump can be handled by two persons and lifted by four. Most HydroSubs are equipped also with a winch arrangement which help lift to lower the pump into the water and retrieve it after the incident.
Delivering the water
With the standard HydroSub 150 , the submersible pump is powerful enough to deliver 3,000 lpm at a pressure of 12 bar. This means that even after 1000 metres of 6” hose there is still enough pressure left to feed a ground monitor without the need for a booster pump.
Should a booster pump be needed, an additional HydroSub 150 can also be used. By removing the inlet strainer on the submersible pump, which is connected by a Storz connection, a 6” hose can be connected and the submersible pump is ready to increase the pressure in a relay system.
For the greater capacities (11,000 - 22,000 lpm) the HydroSubs are equipped with an additional boost pump inside the power pack. The submersible pumps each deliver 11000 lpm @ 2.5 bar into the booster pump where the pressure is increased to 12 bar.
Other solutions include special vehicles with integrated submersible pumps. The vehicles diesel end PTO provide the power to drive the submersible pump. For example, six of these special 4x4 vehicles have been delivered to PEMEX refinery in Mexico.
The vehicles have a 4,000 litre water tank which can be used for direct fire fighting. The vehicle carries over 1,000 metres of 6” hose and a hose recovery unit. If the 4,000 liters is not enough, the integrated submersible pump can be deployed to set up a water supply system with the 1,000 metres of 6” hose.
Large Diameter Hose Systems
The HydroSub makes it possible to get access to any open water source quickly, efficiently and with a minimum of manpower. The next issue is how to set up a water transport system quickly, efficiently and with a minimum of manpower.
Most important is to pick the right diameter of hose; a 2.5” hose can never deliver more water than a 6” hose. A 6” hose cannot deliver more water than a 12” hose.
Friction losses consume a big part of the pumps pressure output, resulting in extra boost pumps needing to be added to the system to transport water of longer distances. Think big - consider 6” hose to be the absolute minimum hose diameter to be used in any water transport system with capacities over 3,000 lpm.
The pressure loss over 100 meters 4” hose when flowing 3,000 lpm is 1.7 bar, while a 6”hose has a pressure drop over the same distance of 0.3 bar!
Hose Laying and Hose Recovery
Manhandling LDH is no longer an issue when using the right equipment. A pod system Hose Layer Container (HLC) can store up to 3000mtr of 6” hose in lay flat configuration.
Using the pod system, several HLC can be handled by a single truck. Laying hose can be done with speeds of up to 30 mph. With this system, during the Buncefield incident, a total of 33km of hose was deployed in a matter of hours.
Even 10” and 12” hose layer containers will hold enormous amount of hose which one driver can easily deploy in a minimum of time. Recovering hose is made easy with the Hose Recovery Unit (HRU). This hydraulic driven tool can recover coupled hose with a speed of up to 4 km/hr, meaning 3000 meters 6” hose can be recovered in 1,5 hours with only 3 persons.
The HydroSub has been developed over twenty years ago for the Dutch Fire Brigades and Civil Protection Services and is being deployed on a daily basis during large fires and flooding. Over this period more than 400 HydroSubs 150 have been delivered worldwide. Many large refineries and chemical plants do not solely rely on their fixed water supply system anymore and have invested in a mobile large diameter water transport system.
The system has, on many occasions, demonstrated its power and ease of deployment during many large incidents, like the refinery fires in Izmir (Turkey), Münchmünster (Germany) and Buncefield (UK), during flooding in Holland, Carlise (UK) and Glastonbury (UK), flooding in Prague (Czech Republic) and France.
Over the last twenty years Hytrans Fire Systems has continued to develop the system and at present there is a full range of HydroSubs and Hose Layer Systems available to cover every eventuality, from small fires to large industry fires requiring vast quantities of water to be transported over long distances.
