Required flow rate

[Mike Buckley]

Looking at the hose pressures if you need 10 bar at the pump for the automatic nozzles, then the standard pressure test for the lay flat hose will have to be 15 bar (according to the old drill books). If you then add in extra pressure for height loss can the delivery hose take the pressure?

I would agree about under pumping, I was always trained to supply 4 bar pressure, give or take a bit, at the pump and then increase or decrease the pressure if requested by the branchman. How many times have yelled "Water on, number 1 line, 4 bars pressure, working on the ......floor" happy but hoarse days!

[Paul Grimwood]

Looking at the hose pressures if you need 10 bar at the pump for the automatic nozzles, then the standard pressure test for the lay flat hose will have to be 15 bar (according to the old drill books). If you then add in extra pressure for height loss can the delivery hose take the pressure?

I would agree about under pumping, I was always trained to supply 4 bar pressure, give or take a bit, at the pump and then increase or decrease the pressure if requested by the branchman. How many times have yelled "Water on, number 1 line, 4 bars pressure, working on the ......floor" happy but hoarse days!

I agree Mike. In those days we were pumping to type 'A' smooth-bore branches or deflector type spray nozzles that functioned on nozzle pressures around 2-3 bars. I am amazed to find that several fire authorities are still training recruits to do this! This is a complete misinterpretation of water management, modern branches and fire-ground needs.

The pressures needed to flow automatic or combination branches in some high-rise situations will exceed the safe working design limitations of Dry Risers - 10 Bars! Nobody seems to appreciate that we are sending firefighters into potential infernos armed with peashooters! Its no wonder that firefighters in several parts of the country have been beaten off the fire floors because the jet they were using offered 'little or no effect on the fire'!

[wee brian]

The guys that came up with modern compartment techniques were, apparently, unaware of gravity.

The standards for risers have changed now but I doubt all the brigades have made the necessary ops changes (new hoses/branches & SOPs)

[Mike Buckley]

wee brian wrote 'The standards for risers have changed now but I doubt all the brigades have made the necessary ops changes (new hoses/branches & SOPs)'

So will the crews be faced with a situation where they have to decide whether or not their kit will work because of the age of the tower block they are looking at? Or do they carry the old branches to deal with fires in the older buildings?

It looks like a receipe for choas.

[Paul Grimwood]

The guys that came up with modern compartment techniques were, apparently, unaware of gravity.

The standards for risers have changed now but I doubt all the brigades have made the necessary ops changes (new hoses/branches & SOPs)

The changes in BS for rising mains were driven by the BDAG research - FRS Circular 71/06 confirms 10 bars is still the maximum charging pressure. They based this on two factors -

1. Modern Swedish compartment firefighting methods mean we can apply less water more effectively and (theoretically) get increased performance

2. 51mm hose should be used on upper floors to reduce the friction losses from outlet to fire

What this attempts to achieve is higher nozzle pressures through an increase in hose diameter (45 to 51mm) to meet the needs of modern branches.

However, the amendment fails to acknowledge that 100mm rising mains were designed to operate with 2-3 bar smooth-bore nozzles and minimum flow-rates of 500 l/min were the objective. With the flows now down to around 200 l/min on the upper floors can we honestly get increased performance by using pulsed or bursting water droplet patterns? No way! Our tactics in ISO containers rely on the fact that the Swedish approach only works in small areas and against limited fire heat release. If a wind gets blowing on upper floors (it did in Glasgow this week) or the fire is in a large open plan office area - throw those Swedish tactics out the window!

If you read the BDAG reports there is no mention of flow-rate requirements but it does refer to pressure needs. Unfortunately, pressure alone will not put out a fire.

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