Key Combat Ready Hose

[firemedic781]

So our department started making the switch from economy hose to combat hose. The decision was made rather quickly without really testing other hose for various reasons. One being that the vendor wouldn't let us demo any without purchasing it and we had no neighboring departments running the hose we could borrow it from to try. It hasn't been too bad, I noticed the kink resistance and whip is much better, but it felt harder to advance solo. I just read Dennis Legears' articles Nozzle Dreams and Hose dreams, and now I am thinking twice on the combat hose. I was thinking maybe its a sales pitch from the guy who makes Tru ID hose, but, it actually makes a lot of sense to me now. I wanted to throw this out there and see what you guys think.

If you haven't read his articles, here is the most concerning part that I read.

"The greatest reduction in friction loss in modern fire hose has been created both accidentally and later intentionally by increasing the internal diameter of charged fire hose. It started when the thicker double jackets of cotton were replaced by mold resistant thinner double jackets made of nylon and polyester. At this time the rubber liner remained, however the bowl size of the coupling remained the same leading to a slight increase in the internal diameter of charged fire hose.

Recently, with the invention of lightweight hose, the problem was amplified. Lightweight hose rapidly became the worst offender because the new thinner liners and jackets created a larger internal diameter as coupling bowl size either remained the same or were intentionally made larger in some lightweight hose designs. This gave lightweight hose a larger diameter when charged. This increase in size lowers the friction loss at a given flow and increases the volume of water in the hose. This also means it is heavier when deployed, because it is carrying more water inside of it when charged. Do not let the hose brochure or salesmen mislead you."


We currently have a 7/8" smooth bore tip that we run at 50 PSI and160 GPM on our 200' 1.75" crosslays. With the combat hose coefficient of 6.59 we run them at a PDP of 85 PSI. It appears that the ACTUAL inside dimeter of combat hose when it swells is 1.9, according to Key. This adds extra water, and thus extra weight to the hose lay. Also, I imagine that a larger diameter hose has more surface area contacting with the ground creating more friction. The entire purpose of switching the combat hose was because we thought it was a lighter, less friction loss hose. Now come to find out, I am thinking its a little misleading. Undoubtedly it has a lower friction loss coefficient, because its a larger hose! Its not a 1.75" hose, its a 1.9" hose, and its actually heavier, although their listed uncoupled dry weight appears to be light, at less than half a pound per ft, again misleading. The water weight increased the total charged hose weight from 296 pounds to 321 pounds when compared with Tru ID hose. Here we are thinking we are being efficient, and we actually have a larger hose that is providing more water and heavier to drag around while flowing the exact same GPM with our same nozzle as before. With the 7/8" the PDP would go from 85 PSI up to 130 PSI following the switch in hose from combat to tru ID. However, this is still under 150 PSI and doesn't affect the pump capacity. Unless we ever ran into the situation where we had a really long 1.75" lay that pumped up to 200 PSI PDP, then our capacity would reduce from 1500 GPM to around 1,000 GPM. It seems the combat would actually be better paired with the 15/16 tip and that may be cheaper to maximize the larger diameter hose and utilize the extra water (185 GPM) we are dragging around, as well as be substantially cheaper than replacing all this new hose. I wont bore you with all the math, and disclaimer, some of my math may be a little off. But, if you're curious on how to find the weight of the hose line; take the diameter of the hose, divide it by 2 to find the radius, then square the radius and multiple it by pie. Then, you take a 50' section and turn it into 600 inches and multiple those. This will give you cubic inches, then divide it by 231 to get from cubic inches to gallons. Then multiple that number by the weight of water, 8.34, and that will give you the weight of WATER per 50' section. Now add the weight of the hose itself, in this case 0.38 lbs per ft, and multiply by however many sections of hose you have. Clear as mud?

The change may seem negligible to some, however, I was thinking that we make the switch from combat to Tru ID before we get really invested in it anymore than we already are. As for our 2.5" lay, we currently have combat for it as well and they have an elkhart chief 4000-26 nozzle that does 250 GPM at 50 PSI. The hose actually swells to 2.6 ID, with a bowl size of 3" and has a total charged weight of 568 pounds. I was also thinking of recommending the switch to Tru ID here, but going with their 2.25" hose as this would reduce the weight to 456 pounds and better be paired with a 1 and 1/8 " tip flowing more water at 265 GPM. This would give us a lighter, thinner hose with increased GPM, although the nozzle reaction would jump from 89 to 99. The tip size of 1 and 1/8 fits perfectly to the 1/2 diameter rule, matching the 2.25" hose.

Thoughts?

[HuntPA]

We switched all of our attack hose a few years ago. We actually have sales reps around here, and not salesmen that just want money. That means we got to test all the hose out there. We ended up with Mercedes KrakenEXO. For us it had the best kink resistance and fell right in line with friction loss when compared to similar hoses. We also made the switch to 75psi nozzles from 100psi nozzles. This took our starting PDP from 165psi to 105psi. This correlates to a lot less stress on the pump and flexibility when adding additional lines on a large fire.

While I understand your point on the reduced felt friction, there are trade offs. #1 being the cost. You own the combat hose and TruID would be a complete purchase. How do you justify that to the board, community, or wherever you get your funding? #2 in kink resistance. In our testing of the hoses, While flowing 150 gpm at 75 psi on the nozzle, we could do a 14" 180 turn with the Kraken. Combat was around 24-28". What is it for TruID. If I am in a structure, I will gladly pull a little harder if it means that I can make all of the bends and turns inside the house without worrying about kinks and reduced flow. #3 You are now running the engine harder. While modern pumps and diesel engines aren't overly stressed by the difference, look into what other hoselines you will be placing in service at the same time and the overall affect on the pump. For us, we looked at a large fire. We pull 2 small lines = 300 gpm at 105 pdp. We then place 2 larger lines in service = 500gpm @ 95psi pdp. Now if we add a blitzfire or other similar ground monitor we are looking at 475 gpm @ 85 pdp. This is relatively easy to accomplish by gating outlets to reduce pressures in a given line. Going with TruID where you show a 45psi pressure increase at the pump. So now we would have our pump with discharge pressures ranging from 85 to 150 psi. This is where I see significant issues unless you have some really good pump operators.

In the end though, what I will say is this......find a real hose rep that will let you test the hose. If the salesman won't let you try it (even in a parking lot just to drag it around) then don't buy it from them. When we did our test we had Mercedes, Key, and All American all there at the same time so that we could directly compare them both with numbers from gauges, but also through direct "feeling" of the hose.

[Rural840]

Interesting that you began the move to “premium” lower friction hose, and now are thinking that maybe that was not the best idea. I am aware of one other knowledgeable fire leader who has some KrakenEXO premium hose, and mentioned that he was considering TRU-ID instead. I was surprised when he mentioned that he was considering TRU-ID because he had gone to considerable effort and expense to select and purchase KrakenEXO. He too was impressed with the low pump discharge pressure required to achieve the target flow. They were using a 150 at 50psi combination nozzle, which is only slightly lower flow than your 7/8 smoothbore (161 gpm at 50psi). Although the manufacturers mention how very smooth the hose lining is, my perception is that the diameter increase nets the majority of the reduction in friction loss.

Another perception of mine is that the premium hoses, i.e. 1.75” that are closer to 2” I.D. can provide the most benefit to users of 100psi nozzles. With 50psi nozzles, the reduced friction may not be as much benefit. As you mentioned, larger diameter hose is heavier when charged because it contains more water. There is a discussion thread regarding 2” hose, and that is something that I feel would be worth considering. I am not aware of any departments nearby using 2” hose, and I suspect that possibility would be rapidly shot down at my VFD. We use mostly 100psi automatic nozzles, so could benefit from lower friction.

Since you are considering smaller hose, I took a look at two possibilities. First, 1.75” actual I.D.; C=13.2 This coefficient from Key Hose is a bit lower than the traditional published C=15.5 for 1.75” hose with 1.5” couplings. Supposing the standard nozzle pressure is 50 psi, and one can have an effective stream from 40 psi to 60 psi (for handheld smoothbore). The numbers I got are:
40 psi at nozzle, 144 gpm, 95 psi PDP(pump discharge pressure)
50 psi at nozzle, 161 gpm, 120 psi PDP
60 psi at nozzle, 176 gpm, 145 psi PDP

You mentioned that PDP would be 130 for 1.75” actual I.D. I got 120, so I would be interested in how you arrived at 130. My numbers could be wrong. If they are, it is not on purpose.

Second, since you are interested in reducing the weight of charged hose – consider 1.5” hose. The published “standard” coefficient is 24. The friction loss calculator on the Key Hose website gives 27.2 and 27.3 respectively for 1.5” BIG-10 and ECO-10. I used C=27 in my calculations.
40 psi at nozzle, 144 gpm, 150 psi PDP
50 psi at nozzle, 161 gpm, 188 psi PDP
60 psi at nozzle, 176 gpm, 230 psi PDP

It seems that both smaller hoses could work with 7/8” smoothbore. PDP is less than 150 psi at all three flows for 1.75” actual I.D. For 1.5” hose, PDP for overpump to 60 psi is higher (230 psi) than I am accustomed to for typical firefighting. If there is money to be saved, and the charged weight is less, maybe it is worth seriously considering smaller non-premium hose.

The above looks only at a single 200 ft preconnect. How do the pump discharge pressures relate to your 2.5” lines? Suppose you also deploy a 200 ft 2.5” with 250 gpm at 50 psi nozzle. Your Combat Ready 2.5” needs 73 psi PDP for 250 gpm. At PDP=85 (same as your 1.75” preconnects), the nozzle will be at about 270 gpm and 59 psi. This is overpumped, but not above 60 psi. Same PDP as preconnects, no adjustments at pump panel. It could be gated to 73 PDP, but that adds complexity at the pump panel, and you needed a big line or you would not have stretched the 2.5”, correct?

Suppose you switch to TRU-ID 2.25”. At PDP=85, the nozzle is only a gallon or two above 250. This looks like the ideal hose to complement the 200 ft Combat Ready 1.75”. Same PDP for both lines. Simple at the pump panel.
Of course, this is looking at 200 ft 1.75” preconnects and 200 ft big water lines. If these lines were longer, you have lots more than 85 psi available from your pump.

[HuntPA]

1.5" @ 200' = 154 pounds
1.75" @ 200' = 208 pounds
2" @ 200' = 272 pounds

[firemedic781]

1.5" @ 200' = 154 pounds
1.75" @ 200' = 208 pounds
2" @ 200' = 272 pounds

what hose is this for?

[firemedic781]

Interesting that you began the move to “premium” lower friction hose, and now are thinking that maybe that was not the best idea. I am aware of one other knowledgeable fire leader who has some KrakenEXO premium hose, and mentioned that he was considering TRU-ID instead. I was surprised when he mentioned that he was considering TRU-ID because he had gone to considerable effort and expense to select and purchase KrakenEXO. He too was impressed with the low pump discharge pressure required to achieve the target flow. They were using a 150 at 50psi combination nozzle, which is only slightly lower flow than your 7/8 smoothbore (161 gpm at 50psi). Although the manufacturers mention how very smooth the hose lining is, my perception is that the diameter increase nets the majority of the reduction in friction loss.

Another perception of mine is that the premium hoses, i.e. 1.75” that are closer to 2” I.D. can provide the most benefit to users of 100psi nozzles. With 50psi nozzles, the reduced friction may not be as much benefit. As you mentioned, larger diameter hose is heavier when charged because it contains more water. There is a discussion thread regarding 2” hose, and that is something that I feel would be worth considering. I am not aware of any departments nearby using 2” hose, and I suspect that possibility would be rapidly shot down at my VFD. We use mostly 100psi automatic nozzles, so could benefit from lower friction.

Since you are considering smaller hose, I took a look at two possibilities. First, 1.75” actual I.D.; C=13.2 This coefficient from Key Hose is a bit lower than the traditional published C=15.5 for 1.75” hose with 1.5” couplings. Supposing the standard nozzle pressure is 50 psi, and one can have an effective stream from 40 psi to 60 psi (for handheld smoothbore). The numbers I got are:
40 psi at nozzle, 144 gpm, 95 psi PDP(pump discharge pressure)
50 psi at nozzle, 161 gpm, 120 psi PDP
60 psi at nozzle, 176 gpm, 145 psi PDP

You mentioned that PDP would be 130 for 1.75” actual I.D. I got 120, so I would be interested in how you arrived at 130. My numbers could be wrong. If they are, it is not on purpose.

Second, since you are interested in reducing the weight of charged hose – consider 1.5” hose. The published “standard” coefficient is 24. The friction loss calculator on the Key Hose website gives 27.2 and 27.3 respectively for 1.5” BIG-10 and ECO-10. I used C=27 in my calculations.
40 psi at nozzle, 144 gpm, 150 psi PDP
50 psi at nozzle, 161 gpm, 188 psi PDP
60 psi at nozzle, 176 gpm, 230 psi PDP

It seems that both smaller hoses could work with 7/8” smoothbore. PDP is less than 150 psi at all three flows for 1.75” actual I.D. For 1.5” hose, PDP for overpump to 60 psi is higher (230 psi) than I am accustomed to for typical firefighting. If there is money to be saved, and the charged weight is less, maybe it is worth seriously considering smaller non-premium hose.

The above looks only at a single 200 ft preconnect. How do the pump discharge pressures relate to your 2.5” lines? Suppose you also deploy a 200 ft 2.5” with 250 gpm at 50 psi nozzle. Your Combat Ready 2.5” needs 73 psi PDP for 250 gpm. At PDP=85 (same as your 1.75” preconnects), the nozzle will be at about 270 gpm and 59 psi. This is overpumped, but not above 60 psi. Same PDP as preconnects, no adjustments at pump panel. It could be gated to 73 PDP, but that adds complexity at the pump panel, and you needed a big line or you would not have stretched the 2.5”, correct?

Suppose you switch to TRU-ID 2.25”. At PDP=85, the nozzle is only a gallon or two above 250. This looks like the ideal hose to complement the 200 ft Combat Ready 1.75”. Same PDP for both lines. Simple at the pump panel.
Of course, this is looking at 200 ft 1.75” preconnects and 200 ft big water lines. If these lines were longer, you have lots more than 85 psi available from your pump.

I couldn't find the coefficients for Tru ID hose on Keys website, so, I assumed it was the standard 15.5 and not 13.2 for their 1.75" Tru ID.

We looked at doing the 2", and using the 1" tip for flows of 210 GPM, but every chart I have seen and article I have read states that the 1" tip is the odd middle man that either offers too much on smaller lines and not enough for bigger lines and no one uses it when comparing the nozzle reaction.

I think we have come to the conclusion that we are going to keep the 1.75" (1.9) combat hose, but switch the tips from 7/8 to 15/16 and take advantage of the extra water/weight and increase the flow on our initial attack lines.

However I am still undecided on the 2.5". We have 3" on the back, and I was contemplating switching the 3" for 2.5" so we had additional hose in the same diameter. But In comparison with standard 3", the 3" outshines the 2.5" when talking about defensive fires and high flows. For longer lays supplying other engines or ground monitors/deck guns, you want the lowest PDP possible to maximize pump capacity. Just going from 150 PSI to 200 PSI drops our Pierce PUC from 1500 to 1,000 GPM. That limits us to only our 500 GPM deck gun and 500 GPM ground monitor without the ability to flow additional lines. So, we are keeping 3" off the back, and unfortunately we have to only choose 1 between the 2.5" or 3" off the back. We have a rescue pumper so we only have 2 trays, 1,000' ft of LDH 5" and the 3". We have a 100' Cleveland load with a gated wye that we attach to the 3" for a courtyard lay if needed, the engineer just has to count the number of sections of 3" that come off the back. The issue is storage, we have the bumper line and crosslays, but we don't have any EXTRA hose to add anything if needed to any of our preconnects without robbing from another preconnect. If we stick with the 2.5" or even if we go with 2" or 2.25", we will only be able to fit 200" of it on the pre connect and thats it unless we store rolls in another compartment. I would have liked to have added another divider to the rear hose bed and add the extra 2.5" up there with the LDH and 3" but with the rescue pumper having the coffin storage on both side up top it really cuts into our hose bed. I did look at doing the Tru ID 2.25" in comparison with the combat 2.5". If we used the same nozzle, our 250 at 50 combi, we are looking at the difference of 568 pounds, 72 PSI PDP and 89 pounds NR with the combat vs 456 pounds, 83 PSI PDP and the same 89 PSI NR on the Tru ID. SO, we could switch from 2.5" combat to 2.25" Tru ID, reduce the overall weight of the hoseline by over 100 pounds while keeping the same GPM, nozzle reaction and without any significant increase in our PDP. Once we try adding the 1 and 1/8" SB tip to it and increasing the GPM to 265 it shoots the nozzle reaction up to 99, but is still manageable. In theory, the 1 and 1/8" tip pairs perfectly to the 2.25" hose. I have reached back out to the vendor in an attempt to demo some more hose, we will see.

[HuntPA]

2.5" @ 200' = 425 pounds
2.25" @ 200' = 344 pounds

I am giving you the weight of the water in each size hose. Obviously each hose weighs differing amounts based on size and manufacturer, but with the diameter given, these are the weights of water you are dragging around.

[Rural840]

Key publishes more hose coefficient information than any other I have found. The coefficient I used for Tru-ID came from their Friction Loss Calculator, under the Resources tab. When you enter 100 gpm and 100 ft of hose, the resulting friction loss is the coefficient. Not a perfect world, though. The PDF brochure for Combat Ready says C=6.59, and the Calculator says C=7.05. Not a huge difference, but would sure be nice if both references provided the same coefficient.

On your 1.75 Combat Ready, If you move from 7/8 to 15/16 smoothbore, looks like you will need 95 psi PDP to get 185 gpm at 50 psi. That is still a relatively low PDP, with plenty of room to increase if needed. Since almost all smoothbore nozzles are break-apart, you can change to a much smaller tip for overhaul, or small fire.

Regarding your 2.5 preconnect; the 250 at 50 that you have equates to 1.09” smoothbore. A 1.125 smoothbore (266 gpm at 50psi) is only a bit more flow. Seems like that is why Elkhart, for example, offers a 265 at 50 combination tip in their Chief XD line. It is equivalent to a 1.125 smoothbore flow. You already have the 250 at 50 nozzle. Is a new 1.125 smoothbore going to be that much benefit? If you are going to buy a new smoothbore, it might be worth considering 1 3/16 or 1.25 that could also be used on your 3” hose for a big flow line. Overpumped to 60psi would be easy on a 3” hose, and the 1.25 will flow 328gpm. The bore dimension change from 7/8 to 1.25 is not all that much, but there is a significant difference in flow.

It seems like owning as few hose sizes as reasonable is a good goal. As you mentioned, 3” hose has a significant advantage over 2.5” when considering flow capability. Certainly 3” charged hose is heavier than 2.5”, which makes it more challenging to use as an attack line. It seems to be typically considered a supply hose. Would 3” hose fit in your preconnect bed? If you eliminated 2.5 hose, that is one less hose size to inventory. 3” is a bit large for an attack line that needs to be advanced. That might not be practical, even if it would fit in the preconnect bed.

So many possibilities, and what works for you is what is right for you. The concept of having all your standard attack lines work well with the same pump discharge pressure seems like a good goal, too. Keep the pump operator’s job simple.