# Thread: Low Pressure Break Apart Nozzles

1. Larry Stevens, Fire Rescue Magazine:

Your correct about the formula not applying to all nozzles. There is a different one for smooth bores. The only reason I posted the formula was to answer S. Cooks question on where the numbers came from.

If the formula is not corrrect as you state am I to assume that Jim Cottrell with TFT was wrong regarding the reaction test compared to the formuala. You may recall the article you ran in Firefighter News about it several years ago. Jim did a fine job presenting the physics that support the formula. I know that he still teaches it in his fire flow classes and even hands out the info on disk. Im sure if you contact him he could provide you with a copy to confirm the formula is accurate.

Im sure you didn't mean to say that the line S Cook was holding had ZERO reaction. We all know that simply is not the case.

Again, you are correct in the fact that hose handling is an art, if not mastered, the hose can make life misserable because of the REACTION.

My post on this subject was not intended to promote or degrade anyone or any nozzle. It was intended to simply be thought provoking and not start an argument with a competitor or its supporters.

S Cook: The answer is simple. There is difference in inch pounds and foot pounds.

Share the Knowledge!
Kirk Allen
First Strike Technologies, Inc.

[This message has been edited by KEA (edited January 28, 2000).]

2. /The answer is simple. There is difference in inch pounds and foot pounds./

I agree - there is a big difference between inch and foot pounds, so maybe I missed something, where/when did we switch from inch pounds to foot pounds? I can't find in referenced anywhere except Capt. Zada's post

3. S Cook:
Page 5-113 of the NFPA Fire Protection Handbook 17th edition. When expressing measurements it is customary to us "pounds" to represent foot pounds and when a more specific measurement is used you will see "PSI", which is pounds per square inch.

Note the description of each factor used in the formula
NR= Nozzle reaction, LB
NP= Nozzle pressure, PSI

That may be where the confusionn came from.
If you would like to convert PSI to foot pounds simply multiply psi by 144.

Kirk Allen
First Strike Technologies, Inc.

4. So, I gather the the 87 pounds nozzle reaction you posted is foot pounds.

If I'm right, then I can divide that by 144 to get inch pounds = .61psi.

Then dividing 75 pounds nozzle raction(from the 150gpm@100psi nozzle reaction the formula you posted) by 144 I get .52psi

Am I right so far?

If yes - I still have more pressure going backwards than forwards.

If no, where's my mistake?

5. S. Cook: You lost me on your math. Please post the formula your using and plug the numbers in so that it can be reviewed to better understand the point your trying to make.

/dividing 75 pounds nozzle raction(from the 150gpm@100psi nozzle reaction the formula you posted) by 144 I get .52psi/

That would be .52psi reaction. .52 psi is more than the 100 psi nozzle pressure.

/I still have more pressure going backwards than forwards /

.52-psi is not more than 100 psi.

IF you can prove this wrong you will have disproven one of Newtons laws of physics.

Sorry if I have made this confusing.

Kirk Allen
First Strike Technologies, Inc.

[This message has been edited by KEA (edited January 28, 2000).]

6. Hey, I'm way lost, but I think I've figured it out.

After reading and re-reading all the related posts, it seems that once a drop of water leaves the nozzle, it's force is converted to foot pounds.

Is that a true statement?

If so, then the 75psi nozzle pressure is actually 10,800 foot pounds in the hose that drops to 87 after it exits the nozzle.

I have decided to end all the questions, and confusion (cheers from the crowd)!

In the next few weeks, I will be setting up a test stand and testing all the nozzles I can get my hands on using a digital flow meter and a strain gauge.

I will test and provide actual nozzle reaction vs flow and any other results that I can find.

In the event you want to include the Vindicator I am sending you a shipping address via email.

If Rod or any other mfg wants to send a nozzle for testing, let me know and I'll send you the shipping address. (Elkhart - we're loaded with SM 20 and 30s)

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