Smooth Bore Branches

[Crog]

2 hours ago, Becile said:

@Crog have they done any real scientific analysis to say that the size of tip your using is optimum for high rise, it really is worth trying some of the other tft tips as a comparison.(they used to come in set of 3 stackable)

Not sure, all done before I started. All info I’ve given is what I’ve gleaned from our SOP’s and case studies around flow/high rises (I’m sure we did this joined with GMFRS). No specific courses were given on the branch as such.

The tip is bog standard screw fitting and only one I’ve seen we have for it (think the CAFS reels have different, but not at a station with one). Having seen the price in Jamie’s link, I doubt we have other tips.

@Jamiejet Thats the one, just with our coupling on and not US.

[Carl]

Im pleased to see someone who's posts, started off in the recruitment sections, complete with a Success Story and now posting in the Ops Sections. 

Well done @Crog

[Jet]

@Steve I can sympathise totally with your last point. I am right in the bracket of people who were just 'doing my job' and never really questioned what or why I was doing it. Like you say, not because I didn't care though. But now I am really starting to question some things, and thinking about smooth bore branches has made me unfold some different methods and approaches that are totally going amiss in our standards and culture. I think that fog attack or however you want to describe it is definitely a welcome tactic in my eyes, but has it's limitations. Which becomes a problem when it's literally ALL you're taught and the expectation is you will approach every compartment fire with those tactics, despite evidence that there is a myriad of situations where it will be ineffective. As @Keith pointed out, sometimes big fire just needs big water and I can't think of anywhere on the current training syllabus that describes a situation where you are in a very large, ventilated compartment and the best thing really is to just take in a 45 with a fit for purpose branch and wash it down the road.

Don't worry Steve, I will continue your fight. I just fear that as a lowly firefighter my influence will be very limited. I would love to go on courses and equipment trials and travel abroad to gain a different perspective, but it just doesn't seem to be the case that they trust the very people that have to use the gear in anger to have any real say in the direction we go in.

EDIT: A very interesting article (and website in general). Has anyone else come across it?

High Rise Firefighting: Branches (Nozzles)

[Becile]

I am one of those that still question the correct branches and flowrates, much to many of our fleet engineers disgust, even to the point where I've been ordered to apologise when I told one of them he didn't know what he was talking about. (That didn't go well !!) Also had our high pressure pumps engineered to deliver through the 33mm hosereel for greater flows (engineering reversed after crews claimed it weighed too much now !!)Oh well....

I've been involved in most of our innovation projects and pump reiterations, they all have their place, but a reliance on one methodology for internal firefighting is folly in my opinion.

If you want to back all this up with some meaningfull statistics and evidence,  you can't go too far wrong than eurofirefighter 1 + 2 by Paul Grimwood.

I'll keep up the crusade too @Steve

[Firestorm]

You beat me to it Keith.

Some excellent posts here and also a lack of organisational learning.

[Jet]

@Becile I would love to get my hands on Paul Grimwoods books. But at £60 on amazon I might have to wait until next Christmas (what a sad Christmas present 😂)

[Ian]

I have added our policy document on our smooth bore branch for your reading?

TECH 2116.pdf

[Ian]

For those that have read the above document, here is the context behind it.

The spray/fog/nozzle is our default nozzle and is always attached to the branch body and is used in most day to day applications. this has 3 flow settings 250, 375 & 500lpm @ 7 bar pressure. This nozzle can be easily changed to one of the smooth bore tips either 15, 19 or 24mm tips.

At a high rise fire the attack jet will have the spray/fog nozzle attached and the safety/back up jet will have the 24mm tip attached. This configuration of nozzle can be changed dependant on the fire conditions or used without any nozzle or tip to get the best flow rates but at a reduced throw!

[Crog]

We have 3 different branches for them. The smooth bore has a 22mm tip capable of 750lpm. Then have midmatic capable of 600-650lpm and the ultimatic capable of 400lpm. The ultimatic is also on our hosereels capable to 120lpm, although new pumps are going to 22mm reels, increasing the flow to 250lpm.

In theory, we won’t use a different branch on second line if smooth bore is in use. We would have both with smooth bores. Not seen it in real world, so not sure how strict jo’s Would be on that.

[OscarTango]

On 01/01/2019 at 21:34, Becile said:

If you want to back all this up with some meaningfull statistics and evidence,  you can't go too far wrong than eurofirefighter 1 + 2 by Paul Grimwood.

@Steve

Great couple of books. Heavy influence of Grimwood in Kent (think he was a KFRS man for a while). For an extra nerdgasm here's the equipment manual for the 22mm the WT carry on the Kent trucks. Also an Ops article about mixing branches that may be of interest.

Noticeable absence of smoothbore branches in Surrey. Something in the pipeline for the future @Becile?

Smooth Bore Branch - Equipment Manual.pdf

Effective Use of Branches at High Rise Incidents - Ops Article.pdf

[Becile]

Actually @OscarTango they are on the pumps! ...the cafs branch is a smooth bore nozzle and can be used for this purpose.(without the front part of the branch) and indeed I taught this all those years ago when cafs was  rolled out to the service, although this seems to have been forgotten, have a go !

[OscarTango]

Aha! So a bit like the Kent CAFS ones then. Only got a NAFS system at ours, was looking for "freestanding" ones such as you'd find in a high rise bag. I'll bear that in mind!

[Jet]

I've looked at our technical data sheet for the Delta 750 combination branch which states that it is fully operational at 2 bar. That doesn't marry up with Delta's tech data which states minimum pressure at branch of 3 bar. Either way, I think I know what answer I'm going to get if I suggest incorporating smooth bore branches within high rise tactics (especially as it's been done before).

But regardless of whether you use a smooth bore or combination branch, this topic has highlighted the issue of pulse spray/gas cooling to be ineffective over the ninth floor of a high rise. I wonder how many FF's and IC's are aware of this?

[Noddy]

Enough to fill a phone box I reckon 

[Carl]

Link is working fine as far as I can see @BRV ?

[Cashybai]

It was one of the big bones of contention that following on from the initial Flashover/backdraft packages post blaina/leo's (remember the tiger in the flames video) the whole gas cooling package became the ONLY way to fight fires. The direction London's training took was unfortunate and misdirected, to the extent of seeing individuals pulse spraying waste bins and in one case a fully involved car fire. Certainly as a fairly experienced guvnor and FBTI the number of times I told folks to drown it and stop tickling it was way too many. As always it seems to take forever for common sense to prevail, Cleveland roll being yet another example.

[Lihp8270]

15 hours ago, Jamiejet said:

I've looked at our technical data sheet for the Delta 750 combination branch which states that it is fully operational at 2 bar. That doesn't marry up with Delta's tech data which states minimum pressure at branch of 3 bar. Either way, I think I know what answer I'm going to get if I suggest incorporating smooth bore branches within high rise tactics (especially as it's been done before).

But regardless of whether you use a smooth bore or combination branch, this topic has highlighted the issue of pulse spray/gas cooling to be ineffective over the ninth floor of a high rise. I wonder how many FF's and IC's are aware of this?

As a mechanical design engineer who previously worked for a UK Norfolk based nozzle company, I can hopefully bring something to this discussion.

https://www.deltafire.co.uk/assets/product-data-sheets/Attack-750-Data-Sheet6.pdf

The Attack750 if you notice is a minimum RECOMMENDED pressure, but it will still operate at lower pressures.  With regards to switching over from Smooth bore to Fog nozzle, there is an option with the Delta Fire smooth bore nozzle to have an option "fog tip" also.  This allows the user to unscrew the smooth bore tips, and screw in (what is essentially) the front end of an attack nozzle giving both smooth bore option, and jet/spray nozzle option with the same body by carrying an attachment.

Unfortunately, there are some common misconceptions around smooth bore nozzles.  A "combination" or "fog nozzle" at it's correct operating pressure, and operated correctly will provider a straighter jet stream, and longer range. 

The issue with a smooth bore is that sidewall friction of the nozzle produces a velocity difference between the outer, and the centre of the water stream, therefore once it exits the nozzle it tends to pull away and break up.  A combination nozzle with a baffle however has a water velocity that is far more equal throughout the streams cross section resulting in less break up.  There is also a partial vacuum behind the baffle which pulls the stream in tighter too.  Due to having a nozzle with adjustable flow rates, which also operates over a range of pressures.  The nozzle is capable of adjusting the jet beyond straight.  A a nozzle which in it's maximum jet position on the shaper to focuses "beyond straight".  This creates a really narrow focal point in the stream where the water is being deflected back in on itself breaking up the stream.

Instead, for maximum reach the "correct" jet position for the flow and operating pressure is in the position which produces a straight stream, and doesn't focus in on itself.  At this point, you will obtain a greater reach than an equivalent smooth bore at the same operating pressure.

However, a smooth bore will tend to have a greater flow rate than a "fogging" nozzle where both have an equal diameter waterway.  I'm happy to answer any questions if people have any.

There's a good technical reference I have that was written by TFT.  It was an article that although intended as subtle sales pitch of automatic nozzles, it does provide a nice overview of different nozzles in a manner understandable by users, rather than by engineers.  I will try and work out how to upload it so I can share.

[Ian]

1 hour ago, Lihp8270 said:

With regards to switching over from Smooth bore to Fog nozzle, there is an option with the Delta Fire smooth bore nozzle to have an option "fog tip" also.  This allows the user to unscrew the smooth bore tips, and screw in (what is essentially) the front end of an attack nozzle giving both smooth bore option, and jet/spray nozzle option with the same body by carrying an attachment.

What we in Herts have right?

[Lihp8270]

I am only a Mechanical Designer

The only nozzles I know of that specific services have, are those with requirements that deviate from the standard product as there are a few service specific nozzles out there.  Beyond those service specifics that I work on, I wouldn't know who has what I'm afraid.

Edited January 4, 2019 by Carl
Quote removed as its a direct quote of the post above. Please see FAQ

[Jet]

@Lihp8270 So you say that combination branches when operating at their optimum pressure perform better than smooth bores at optimum pressure, which I can quite easily believe (you're the expert after all 😁). But which performs better when the pressure is significantly lower than optimum? I have been under the impression that even with a low pressure supply at the branch, a smooth bore will still provide a good flow rate, the same apparently cannot be said for a combination branch. Or so I'm told.

[Lihp8270]

Ok. So this question is a little more involved than it seems and I’m on a phone so you’ll have to pardon any difficult formatting. 

If you’re using a constant flow nozzle, the combination nozzle should* perform better up until you cannot get a straight stream from the shaper. 

If you have a select flow nozzle, your nozzle pressure is also affected by the flow position. the flow selector works by either moving the end of the barrel closer to the baffle, or the baffle closer to the barrel.  So if you set a nozzle to minimum flow rate, then set your pump to run at 6barG, then use the dial to go to maximum you will notice that pressure drops. In this scenario your pump operator should compensate for you. 

If you now imagine this backwards. Your nozzle pressure drops, since you may not have the pump capacity to get your pressure back, the option you’d have is to reduce the flow indicator on the nozzle. This would give you your optimum throw and stream back.

this is what automatics try and do, they spring load the baffle essentially and it works like a pressure regulating valve. As flow rate increases the baffle opens, as it drops it closes. So as to maintain optimum nozzle pressure across a wide variety of inlet pressures but tbh they’re not all great in my opinion. 

So, your question, you may get greater flow but a select flow combination nozzle with a low flow rate selected may perform favourably at lower pump pressure capacity than a smooth bore, but it does depend on conditions of the test of course. 

If you want to understand how pressure affects flow it can be calculated with the K Factor. It’s not often given by manufacturers. But it is: Q=K*sqrt(p) where Q is flow rate in lpm and p is gauge pressure in bar. So you can get the k factor by doing flow rate divided by square root of the pressure.  Plug this k factor back into the original equation to get the flow rate at different pressures. Regardless of smooth bore or combination, if it does 500lpm@6bar they will have the same K factor, therefore they will both flow the same at different pressures. But with a select flow combination nozzle you can adjust for flow rates to improve nozzle pressure where you cannot with a smooth bore. 

To clarify, you can adjust a select flow to trade flow for range in some low pressure conditions.

But if you drop pressure to a smooth bore and a combination that flow the same at 6 bar they will both flow the same at 3 bar

Edited January 4, 2019 by Carl
Quote removed as its a direct quote of the post above. Please see FAQ

[Cashybai]

Mmm...I get what youre saying in terms of theoretics re combination nozzle vs smooth bore. Just to set the understanding, LFB are currently using Delta Attack 400S Pro, Delta Attack 100 S Pro, Rosenbauer Select Flow RB101, and of late the Rosenbauer Projet II. Now I'm never going to dispute the value of the first three in terms of their gas cooling abilities when in cone spray, however for external firefighting use I'd disagree that  "A "combination" or "fog nozzle" at it's correct operating pressure, and operated correctly will provider a straighter jet stream, and longer range." It's certainly been my practical experience that combination/fog nozzle/teeth equipped branches are extremely susceptible to wind break up of the jet, in the exact polar opposite to a solid core/smooth bore jet . Practically speaking an in effect hollow tube of fine droplets carries little relative inertia in comparison to a 1" solid rod of water, thus the path of said fine droplets is easily deflected. I've previously refered to them as 'Focus' jets, since in effect to get a jet effect you're tightening down the tube into a cone , at that point of focus you get a collision of droplets and a subsequent breakup of the jet beyond said point. I can't quote any of the theoretical principles, all I will say is practically a rosenbauer Projet will throw a jet of water considerably further than a rosenbauer select flow  at the same given pressure/flow rate. 

[Lihp8270]

The "solid rod of water" does only exist for a short period out of the nozzle, due to the velocity difference across the stream a smooth bore will always be breaking up.

With regards to creating a "focus point" where you get a collision of the stream and a break up, that is absolutely correct.  However, that has been "over focussed" the jet position should actually be before that point, where you get a straight stream.  Once you get that focus point you end up with quite a terrible stream.

This is an interesting read for those who are interested, it is produced by TFT.

http://www.lacountyfirefighters.org/items/TFT_guide_to_nozzles.pdf

I cannot dispute your comparisons of the Rosenbauers, as for all the joys of maths.  Theoretical engineering doesn't always marry with the real world.  But from my experience in test cells, the smooth bore falls short of combination nozzles.  When doing this test, is the select flow nozzle focussing beyond straight into a "focal point" or is it set for a straight stream?

[Steve]

On 04/01/2019 at 14:52, Lihp8270 said:

Instead, for maximum reach the "correct" jet position for the flow and operating pressure is in the position which produces a straight stream, and doesn't focus in on itself.  At this point, you will obtain a greater reach than an equivalent smooth bore at the same operating pressure.

However, a smooth bore will tend to have a greater flow rate than a "fogging" nozzle where both have an equal diameter waterway.  I'm happy to answer any questions if people have any.

And this is exactly the point being made here. Of course, there is greater engineering and research into modern combination nozzles and they are designed to provide optimum water 'shape' and 'reach'. However, the point being made, which lots of Ff's don't understand, (because of the misinformed belief of gas cooling being the start, middle and end of compartment fire attack over the last couple of decades, especially in low or un predicatble pressure scenarois, typically with rising mains, is that irrespective of shape, reach, droplet size (and its related cooling efficiency)) is that you still need to overcome the rate of burning. which is all about volume (read flow) of water.

Within a fire compartment, reach shouldn't really be an issue, flow and the ability to overcome the rate of burning is everything. Getting back to my point, when we lost the noble, we were given a great modern combination nozzle, but we lost pretty much half of the flow cpability of the old branch. (approx 900lpm down to 470lpm give or take).

[Lihp8270]

@Steve there are however combination nozzles capable of flowing 900lpm available though.