Smooth Bore Branches

[Jet]

Who carries smooth bore branches on their appliances? I'm keen to hear some pros and cons with them and what specifically you use them for.

[Crog]

We carry 2 on each WT pump, not sure about the on call pumps. 

Pro is greater flow in Lpm over non-smooth bore.

Con is supply tank emptying quicker.

Main use for us is on high rise jobs. We did research around flow rates and pressure using dry risers and found the branch’s we use (mid and ultimatic) weren’t delivering what they should above the 9th floor. Both have optimum working pressure of 6 bar to deliver 400 to 650lpm. Found output above 9th was below 6 bar, reducing effectiveness of the branches. Smooth bore doesn’t have that issue and ones we have are capable of 750lpm at 6 bar.  We have a high rise bag with both branches and 2 lengths of 51mm Cleveland lay ready for taking up to any high rise.

[Jet]

I was aware of the effectiveness of them in high-rise situations and working at low pressure. How do you utilise them in high rises with regard to control of fire gases and modern compartment firefighting techniques?

[Dyson]

Good answer Crog, good to see this level of knowledge is getting out there.....

Regarding your 2nd very good question Jamie, the answer is i suppose that a true smoothbore won't supply the droplets etc that your are referring to, to control those gaseous conditions......there are hybrid nozzles on the market.

If you've got a wind driven fire flying at you down a hallway on an upper floor, you need flow, and this is what the smoothbore offers, and that's why its becoming more popular again. The technique in use will be very different to how we use fog nozzles of course.

Smoothbores are also ideal for external application, in order to reset a fire compartment during a transitional attack.

[Jet]

Thanks @Dyson. I'm glad you say that they are becoming more popular for the reasons that have been stated. I do think we should be given a choice which branch to use and to appreciate the advantages/disadvantages of each type. For me this is a wholly under-appreciated training topic. We carry smooth bore branches in GMFRS but I'll be totally honest in that I have absolutely no idea why; I've just assumed they are for a covering jet if needs be. I'd love to see more training in real fire scenarios with different branch types in use.

You also mention transitional attack. Again something that isn't really taught officially but should be. I just think we get so much training on branch techniques, how to open doors and 'paint' fires but we get nothing when it comes to the bigger picture regarding how we are actually going to put it out based on what we are presented with on arrival.

[Ian]

Jamie,

This topic of smooth bore branches, gas cooling, transitional, direct and indirect attack is a hot topic with us right now and is confused and mis-understood by many which  as you quite rightly state needs to be un-picked and taught.

As has already been nicely explained by Croq , flow is what is required at a wind driven high rise fire with gas cooling techniques being largely ineffective and not the correct technique required. Gas cooling is better used as you are making progress towards the fire (your standard bedroom, kitchen etc) cooling and diluting the fire gasses as you go to make it safer for the crews....... not effective at a high rise fire!

Transitional attack has largely lost its place in training over the years but in fact is a well versed method used by fire crews for decades. A simple example would be rolling up to a well developed and vented house fire coming out of the front doors/windows etc and a 45 or (51 in our case) getting to work immediately to knock down the fire while the BA crew are getting briefed/rigged. The jet is knocked off as the team enters who can then gas cool if necessary and finish extinguishing the fire. What must be recognised now that fires almost certainly CANNOT be pushed around the premise as what was previously thought. To ensure the success of this type of attack the jet must be on a "core" so that the expanding fire gasses and steam have an exit port (ie the door or window that it is being directed through) should you put this jet on a spray you will "plug" the outlet up with the water droplets and then there is nowhere for the gasses and steam to go except back into the fire compartment and beyond, thus reducing survivability rates? this can also be highly effective at a high rise fire if an aerial turns up with the first attending pumps. Getting the water into the fire compartment while a bridgehead is being established is in my opinion the perfect opportunity to make this technique successful!

In a direct attack, droplet size is very important. Droplets that are too small, will not reach the seat of the fire. For this, big, fat droplets are needed. These will fall onto the fuel surface and evaporate. Ideally, the water will slowly run down the burning object. That way, the largest possible surface area is cooled down. This droplet size is very different from that needed for gas cooling. When gas cooling, the nozzle needs to be opened as fast as possible. The higher flow speed of the water creates smaller droplets because the water is flowing through the teeth of the nozzle. When the nozzle is opened more slowly, a lower flow speed is achieved which in turn leads to thicker droplets. Basically the water stream is aimed at the base of the fire!!!

Finally an indirect attack is aiming the stream of water at the ceiling or wall above the flames allowing the water to drop down and extinguish the flames. 

I certainly don't profess to be any expert in this field and I am happy to listen to others views if I am in correct?

[Cashybai]

Another big advantage of smoothbore as against 'focus' nozzles is a solid core of water, apart from having a greater range, less break up from wind effects is that it can be used to shatter external windows by sending solid 'shots' of water at internally warmed high level windows. For those of us old gits can remember the London Noble branch that's one of its better attributes. 

[OscarTango]

A lot of experimentation was done regarding flow rates in Kent after a few incidents which has influenced a lot of the gear carried. Not only smooth bore branches but we all now have two lengths of 90mm hose to maximize flow from a hydrant. 

The whole time pumps have two smooth bores as it was found that mixing branches above the 8th or ninth floor meant the smoothbore would rob flow from the other branch due to the head pressure, regardless of what the pump was putting out. 

The on call have one smooth bore though this is technically a CAFS branch, so while you can us it for water you cannot adjust the flow rate on it.

[Crog]

As others (notably Noddy’s answer) have stated. In a high rise, we’re looking at getting the wet stuff on the red stuff over gas cooling, which the smooth bore is very good for.

As noted by OscarTango, we don’t mix the branches in a high rise job for the attack line and corridor protection, they will both be smooth. The stairwell line should also be smooth if available. 

[Noddy]

Glad I was of assistance Crog 👍although perhaps Ian should receive the plaudits as I haven’t said anything 😂

[Jet]

Some brilliant information there, thanks all for the replies.

Can I ask what model branch you are all using? A picture would be even better as well...

 

[Crog]

29 minutes ago, Noddy said:

Glad I was of assistance Crog 👍although perhaps Ian should receive the plaudits as I haven’t said anything 😂

I was doing so well😂

I’m in tomorrow Jamie, if I remember, I’ll grab a picture.

[Jet]

Cheers @Crog 👍🏻

[Carl]

Nice to see some more operational topics taking place. Let's hope we can attract more members to join in. Im sure many have experiences that could be very useful.

[Dyson]

I’m really pleased we are able to discuss these topics, with a decent level of understanding being displayed here. 

Once we’ve nailed this topic, shall we proceed straight to flowpaths ? 

[Jet]

I’m in tonight so I’ve looked properly at our smooth bore. It’s an Akron Assault 15mm and was indeed utilised in the high rise pack. It’s since been replaced by the Delta Attack 750 which is a fog nozzle and now the smooth bore just acts as a spare for a covering jet. It does seem to be a bit of a backward move given what’s been said on here.

[Crog]

That’s ours. It’s a v1v from tft from memory.

[Jet]

Looks a bit more modern than our offering...

 

[Crog]

Had them for at least 18 months, but not sure how old.  Not the most used item either.

[Becile]

@Crog the tft  model you show has selectable tips, it looks like the tip you have fitted is typically the one that was used with CAFS , as it is probably around 31mm which was the recognised optimum smooth bore for delivery of CAFS.

TFT (leader) do a whole range of sizes, dependant on flow and throw required.

[Crog]

We have a few CAFS pumps around the county, so suspect they got a job lot of the branches at same time as sourcing them.

Its a pretty decent branch, does what it says on the tin.

[Jet]

Is this the same or similar type of branch you have Crog?

[Becile]

@Jamiejet most of the pistol grip , with ball valve can be fitted with any combination of connections and tips , so the pistol grip is the main component and the rest is fitted as required.

BY the way the branch you show on your pump looks like an older Akron grip , but it’s not an Akron tip, so I,m guessing this was adapted by your workshops/fleet.

if you want to see the standard tips available just look at the Akron brass website then the many pages of branches available.

@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)

[Steve]

All of the above is pretty much what I have been saying since they took the smooth bore away from LFB almost 21 years ago in 1998. At that point we needed a combination nozzle..... but the 'experts' (in reality, people looking out for themsleves and their promotion opposed to any real understanding or passion for Firefighting, all too scared to say no to those above) were having none of the argument to replace the ageing AWG branch with a combination nozzle but retain (or replace with a modern low pressure high flow smooth bore) the Noble Branch.

It saddens me that what I knew as a young Junior Officer carried on through to when I was a walrus like retiree and it still hasn't been sorted universally and the associated knowledge what should be week one for all Firefighters still isn't as clear and obvious as it was to some of us 20 years ago.

It isn't my argument anymore, but I am a little comforted to know that their is now a growing recognition of what is required for compartment Firefighting and what is just a small piece of the overall suite of tactics... the little bit about gas cooling which was only ever about the approach to a fire compartment. For a long time, in the Countries biggest Fire Brigade this was 'officially' unknown and not considered. Sadly, too many people (as good and committed as they may be) are just doing a job, so never challenged it and never understood (or cared) enough to back those fo us who did.

[Keith]

Isn't it amazing how things in the fire service always seem to come full circle, imagine big fire, needs big water.

Next thing you'll have someone suggesting a Type A branch.😂