Fire Service Manual - Incorrect Hydraulics Formula

[Paul Grimwood]

The 2001 publication - Hydraulics, Pumps & Water Supplies, from the UK HM Fire Service Inspectorate applied incorrect principles and formula on p77-78 stating that -

'A formula used in the United States, the Iowa rate of Flow Formula, predicts the rate of flow required to control a fire in the largest single compartment of a building when the area is fully involved'

The Fire Service Manual then went on to transpose the Iowa formula into a metric format. However, it used the V/100 version of the Iowa formula which is only viable for a 30 second application. The V/200 version should have been used to derive a Litres Per Minute formula of 2/3 x Compartment Volume in m3.

Therefore Example 1 given on p78 should read -

Flow-rate Required = 2 x 20 x 12 x 3   Divided by 3

=  480 LPM (and not 960 LPM)

Now this answer of 480 LPM in a 240 m2 compartment is typical of the Iowa principles of fire suppression that work on the borders of Critical Flow-rate (CFR).  If applied incorrectly this may be very dangerous. For example, the Iowa principles are founded solely on an indirect attack, relying on steam production smothering the fire to suppression.

www.fire-flows.com

[notty]

Studied hydraulics formulae for many years whilst taking exams etc. Guess what, in 21 years of firefighting I've always gone with the when its out stop putting water on it theory!!!

In the days of the "modern fire service" why do they persist putting rubbish like this in the manuals?

[Paul Grimwood]

Studied hydraulics formulae for many years whilst taking exams etc. Guess what, in 21 years of firefighting I've always gone with the when its out stop putting water on it theory!!!

In the days of the "modern fire service" why do they persist putting rubbish like this in the manuals?

And when do you know if you got enough flow at the nozzle to make a safe approach?!

[notty]

I measure the compartment, then do the maths using a formula printed in a manual (honest!!!)

Providing no-one is hanging out of the windows, or screaming at us to save their property of course.

Top tip coming up here.............................

Little fires little hose (high pressure HR's)
Big fires Big hose !!!

Not very technical, but it works every time

[Paul Grimwood]

Top tip coming up here.............................

Little fires little hose (high pressure HR's)
Big fires Big hose !!!

Not very technical, but it works every time

Thanks for the tip .... tell it to the two guys who were killed at Bethnal Green last year! Oh and the five who were killed in Paris the year before. If firefighting was that simple we wouldn't need training manuals!

Did you know several UK fire brigades are currently flowing LESS water from their 'BIG' hose than they are from their 'LITTLE' hose! So why not tip them off as well while your at it!

[dave bev]

guys, dont get all caught up in this issue - yes it is extremely important and the calcs are there so that designers can manufacture the correct equipment,  brigades can then select the correct equipment and train their staff accordingly - the calculations are extremely important, whether it should be in a training manual is another issue, and as far as asking how you can tell there is enough nozzle flow to make an approach paul, you should know better, and i bow to your better knowledge on this than most people! its not just branches, its hose (different types, kinks and all) pumps and perhaps the most important of all - those 'operators' using the equipment. if we honestly believe a firefighter can tell if a piece of equipment is functioning correctly (though maybe not perfectly) and i happen to believe experienced firefighters can tell (thats not just experienced in terms of fighting fires, it is also relevant in terms of operating any equipment in training scenarios under ideal conditions to gain an understanding of when the equipment is functioning optimumly (is that a word?))

paul is right to highlight the incorrect formula - i wouldnt have noticed it unless i had been specifically tasked to do some work in that area, in which case i would always question anything!!

im sure neither of you are advocating that no experience is required in fighting fires or operating equipment, and just an ability to do dead hard sums would suffice!!

dave bev

[Paul Grimwood]

Dave .... I appreciate your points.

I think flow calcs (needed flow rate to suppress fire in a compartment) is only a very basic 'rule of thumb' guide. Nevertheless these calcs are simple to use, in some situations, and are very easily applied. I agree that some calcs do not serve a fireground purpose but simply exist to enhance a firefighter's knowledge of how his/her equipment functions optimally ;-)

I was at FSC last week and picked up the manual from the shop. I was astonished to see this use of a formula that is not only incorrect but misapplied in the method of suppression that forms the basis of the IOWA calcs. The technical writers obviously had no appreciation of what IOWA firefighting tactics mean!

I had personally developed a reliable 'rule of thumb' formula in metric that was based on OUR firefighting approaches and did NOT need conversion from US to a Metric format. This was first published in 1992.

When a fire officer evaluates and assesses an incident from the outset a prime consideration is taking into account the building dimensions and the percentage and extent of fire involvement. With that information to hand it is very easy indeed to estimate needed flow-rates and resources to deal with the incident as it stands. The make-up should obviously take into acount needed flow-rate requirements.

My other point is that we, in the UK, have become so unprofessional in some areas, that our firefighters are NOT able to estimate reliably (sometimes not even close) the amount of water exiting the nozzle tip, let alone consider if this is a safe flow to commit with.

Amazingly, firefighters are being committed on a daily basis in the UK with unsafe flows!

[dave bev]

paul perhaps we both remember the days of yore when firefighting wasnt a science and by hell some of those oldies new some stuff!

perhaps we both remember the benfits of training with and using and therefore understanding our equipment, its functionality and when it was working the opti thingy word!

without dwelling, i never bought your book explaining it all, i might have read it if it had been bought for me, but the beverley sisters always preferred to buy me socks!

as for you being amazed, methinks you jest! of far more importance is having the correct resources in place - you remember pathfinder, a study that exposed the uk fire service as being under resourced, bdag which is being buried as we speak. whatever happened to the cfoa work streams that were set up to deliver its findings?? and you are amazed that firefighters are being committed with unsafe flows!!

as for make up, start with a good foundation - ive heard thats the real secret of success!

dave bev

[Paul Grimwood]

Dave .... I love the wit

But you know me and I get passionate about these things. There are young UK firefighters who are not going home to their families because of the pompous 'couldn't give a damn' approach by in-power politicians and weak minded Chief 'Executives'.

Safe 'tactical' approaches are within our own reaches .... show me a decent high-rise procedure in this day and age!

Adequate operational resources are being sucked from our service and now are dangerously inadequate in some areas .... with no future for improving!

Training .... yes I remember that word in some distant past!

I will do all I can to bring these issues to people's attention in the public eye. But we need to be getting our own ship's in order and batten down those hatches before the storm really breaks!

[dave bev]

paul a little humor does indeed go a long way - believe me when i say it keeps me sane - and i am one of the few people in the uk fire serivce that has a certificate to say i am sound in mind, i dont know about the rest ot the uk f&rs though!

have you had any involvement with bdag research streams - in particular high rise and unfenestrated buildings?  private me away from here if possible?


dave bev