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38 mm Vs 45 mm Hose

Posted by Shan Raffel
Shan Raffel
“Shan has pioneered and championed a global paradigm shift in fire fighting tech
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on Sunday, 04 March 2012
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What are the advantage and disadvantages of using larger diameter hose?

“The pressure loss due to fiction varies as the square of the velocity.” In simple terms, as the velocity of water inside a hose increases, so does the friction loss. The increase is quadratic, so an increase in the flow by a factor of X will result in an increase in friction loss by a factor of X2. Therefore doubling the flow through a hose will quadruple the friction loss.

If we can reduce the velocity then we can reduce the pressure required at the pump and we can deliver more water over a greater distance.

 

Flow or ease of handling?

So therefore larger hose lines are better? Well it depends. Larger hoses are heavier to drag and harder to manoeuvre. The best solution is to use the smallest line that will deliver the required flow and pressure over the distance required.

Lets consider at situation where we need to supply a flow rate of 475 lpm to a nozzle at a tip pressure of 700 kPa.

For 38 mm hose we will have a friction loss of approximately 257 kPa per 30 metre length. (* Akron FireCalc).

Therefore if we need to deliver this water over 60 metres we will need to have a pressure of 1214 kPa at the pump. ie 700 kPa at the nozzle + (2 x 257 kPa)

If we use 45 mm hose we only need 167 kPa/30 metre length.

So for 45 mm hose we need a pump pressure of approximately 1034 kPa.

In both cases most pumps will be capable of supply the required pressure and flow. 38 mm hose will be easier to handle. If however the need to flow higher volumes of water or add more lengths, the pressure loss through 38 mm hose will be excessive.

It is important to consider your particular application and then choose the hose lay pack that will best suit your needs. The Quick Lay Fire Attack Team have the expereince and the knowledge to ensure you end up the most efficient hose lay combination for YOUR NEEDS!

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“Shan has pioneered and championed a global paradigm shift in fire fighting techniques that are now accepted as standard practice. His expertise in this area is what drives QLFA seamlessly through the industry”

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