# Thread: Calculating PDP for Preconnects

1. ## Calculating PDP for Preconnects

If you do not have a flow meter and you want to calculate your correct PDP for preconnected handlines... Can you use a smooth bore and pitot test it for the flow you are trying to achieve then add 50 PSI if you run automatics or standard combination nozzles at 100 PSI tip pressure?

2. Use the friction loss formulas and calculate the desired flow based on your nozzle type and hose length. If it does not change from call to call, the the Operator knows that they pump the same thing each time a line hits the ground. Put it (PDP) on a label and stick it on the gauge.

3. Cap, Thank you for the reply, however I want to know the actual flow, not the theoretical flow. With 4 90 degree bends before the actual outlet I'm sure this throws theory to the wind. I am fairly knowledgable in hydraulics (im the nozzle guru of my department), just wondering if you can apply my thought practically. We have all of the throretical numbers stickered on the panle already, I want to test and see if they are true, but don't have a flow meter.

4. ## Re: Calculating PDP for Preconnects

Originally posted by MG3610
If you do not have a flow meter and you want to calculate your correct PDP for preconnected handlines... Can you use a smooth bore and pitot test it for the flow you are trying to achieve then add 50 PSI if you run automatics or standard combination nozzles at 100 PSI tip pressure?
What Capt said will work, or you can get a flow chart for whatever brand automatic you use. We use TFT, and downloaded the flow chart for our nozzles from the TFT website. It shows GPM, hose size, hose length and PDP. That comes in handy if you get in a situation where you have to extend a preconnect.

5. MG,
I think I would use the actual nozzle you intend to use on the handline and then place an in-line guage (similar to an AkronBrass style 33) for testing just before the nozzle to give you your inlet pressure.
Then use the nozzle flow chart as Dave suggested.

Decide what flow you want from the nozzle, get the required inlet pressure from the chart, flow the handline and adjust your pump until you get the required nozzle inlet pressure. Read your pump guage for that discharge and there's your PDP for the pre-connect for that nozzle flowing whatever target GPM you selected.

6. Perhaps I should tell you why I want to know the actual flow as opposed to the stuff the companies print out for you. First of all I'm a little bitter about TFT nozzles, a flow test with a flow meter showed they flowed much less than we expected..using the theoretical numbers. In fact we were flowing about 112 GPM when it should have been 150, that goes to show you it pays to flow test. TFT's are notorious for going out of calibration if you dont perform the maintenance on them (oiling the spring or whatever they want you to do). Now that we have saberjets, its easy to flow test and pitot them. I want to be able to do this type of testing on other rigs, as I am an instructor and its nice to be able to substiantiate theory and principles.

7. Originally posted by kfactor
MG,
I think I would use the actual nozzle you intend to use on the handline and then place an in-line guage (similar to an AkronBrass style 33) for testing just before the nozzle to give you your inlet pressure.
Then use the nozzle flow chart as Dave suggested.

Decide what flow you want from the nozzle, get the required inlet pressure from the chart, flow the handline and adjust your pump until you get the required nozzle inlet pressure. Read your pump guage for that discharge and there's your PDP for the pre-connect for that nozzle flowing whatever target GPM you selected.
Sounds like the best suggestion so far, I think I have a gauge like that at the academy.

8. TFT's are notorious for going out of calibration if you dont perform the maintenance on them
I can see that you have had the BS speach from the guy that pulled the wool over your eyes and sold you saber jets. Sorry to hear that. First and foremost, any nozzle or piece of fire equipment that has water flowing through it, has to have maintenance done periodically. This related to the crud and stuff in your water as well as the "hard water" that is prevelant in a lot of places. Elkhart and Akron will have you believe there equipment is "maintenance free." That is why we recently had an Elkhart intake valve (less than 4 yrs old) that required 4 hands and 2 spanner wrenched to open. The mindset was this: "The salesman said just put it on and it would last for ever, much better than my competition." Hmmmmmm....I wonder why when it was replaced with a Competitors BIV that was a DEMO and had travelled across the state for almost 4 years and been used many more times, the DEMO worked fine. Why...it had been maintained. Any nozzle that is not maintained will begin to lose flow. Additionally there is no such thing as a nozzle going "out of calibration" If you send a NFPA Compliant nozzle to TFT for repair (less than 24 hr turn around) they recertify it as NFPA compliant when it leaves the factory by testing it. They do not "recalibrate."

The maintenance that is required/recommened by TFT takes less than 10 minutes to perform. Your TFT nozzles that were flowing "112" GPM....How old? What was the Model? (midforce? Midmatic? Metro I?) What was your pump pressure? What was your length and size of line? It seems you have already said that you do not feel the need to do maintenance so I am betting this is the problem. I once took a TFT nozzle that the Elkhart rep said was no good, (it was 15 yrs old) and spent about 10 minutes with it. We then put a flow gauage on it and amazingly enough it was flowing the same amount at the same pressure as the Elkhart.

If you are concerned about your flow rates because of the piping do this. Put a pressure gauge on the line in question and then charge the line to your desired PDP. Compare the guage pressure for that line against the in line pressure gauge at the discharge opening of the line in question. That will tell you how much pressure loss you have in your piping. At the same time get an in line flow gauge that shows GPM (a good one) and put it on your las 50' of line. This will tell you what your actual GPM flowing is. Compare the flow of the TFT to the Akron.... Would venture to say that if you are comparing apples to apples, you will see that the flow rates are similar. Also look at the effect "gating down" the nozzle has on the Akron or Elkhart. Your stream quality is deflected by the ball. With the TFT, you will reduce your GPM but you will not seem a deterioration of stream quality.

9. A simple pump pressure for pre connected hand lines - 1-1/2": 1-3/4",
with sutomatic nozzles, for 150 to 200 feet of hose line, 130 to 150 PDP. If they want more pressure they will ask for it. Otherwise this is ample pressure for these handlines.

If you are using 2-1/2" hose with 300 GPM nozzles, pump 115 to 130 for these bad boys.

The plumbing on the pump before it gets to the nipple has some affect on the discharge. Normally, this isn't figured in the PDP. Don't go overboard figuring what pressure to pump.

10. A lot of the firefighters in my FD carry the field hydraulics card that is issued to the recruits at the Massachusetts Fire Academy or have a copy taped into the nearest overhead compartment to the pump.

Why reinvent the wheel?

11. MG3610...

I see no reason why the method you suggested in your first post wouldn't work.

By the way, why not ask the salesman who sold you those saberjets if you can borrow an inline flow meter? If he is any kind of salesperson he has one.

The other method is to put an inline pressure gauge right behind the nozzle. Once that gauge reaches the appropriate pressure for that nozzle you know you are flowing what the nozzle is supposed to flow and then check your engine's discharge gauge.

I shake my head at the theoretical method of figuring PDP. Every rig is different, every hose is different. The only true way to know is to actually flow test the lines.

As for TFT's...I love my smoothbores and Elkhart lowpressure nozzles.

FyredUp

12. This is the 3rd time I have had to try to reply, both other times I lost my whole message so this will be shorter.

Cap,

I am not one to be easily fooled by a salesman. I do my homework and am always trying to stay on top of stuff. So, there is no gimmick that was used to sell to us.

In regards to the automatics, we can agree to disagree on this. Ijust am not a big fan, and I totally understand the operation of them. At the same drill, the Elkhart SM30's off another engine were flowing around 160 GPM where the TFT was at 112 at the same PDP. This was confirmed by swapping nozzles, the best we could do with the TFT's at the chosen pressure was no more than about 120 GPM. The TFT's are handline series. They are about the same vinatage as the Elkharts (10-12 years old).

The saberjets have a different design so that the fog stream runs around the circumfrence of the nozzle body, basically eliminating the turbulence you get with a standard ball valve type nozzle that is gated part way open.

In 10 years, my guess is that with no maintenance the saberjet will still flow its rated amount without any oiling compared to the TFT. I am not saying I promote neglecting equipment, what I am saying is that most places dont oil their nozzles.

and so..the battle of the nozzles continues

Oh yeah, the pressure guage on the outlet compared to the discharge guage...I like that idea. When it gets warmer I'll check both ways out to see if they coroborate each other.

Thanks

13. I'm not a math whiz (ok, so I am) so we used a fairly simple method. My tank holds 450gallons. I pumped through my preconnect until the tank was empty and timed it. I then divided the # of gallons by the time and came up with what I was flowing. A little playing back and forth through testing and I found the pressure I needed to pump and get 150gpm from my preconnect. Then, for giggles, we did it using a flow meter. Same results.

14. Originally posted by MG3610
In regards to the automatics, we can agree to disagree on this. Ijust am not a big fan, and I totally understand the operation of them. At the same drill, the Elkhart SM30's off another engine were flowing around 160 GPM where the TFT was at 112 at the same PDP. This was confirmed by swapping nozzles, the best we could do with the TFT's at the chosen pressure was no more than about 120 GPM. The TFT's are handline series. They are about the same vinatage as the Elkharts (10-12 years old).

Well, from my almost 20 years experiance with TFTs, I say you have a bad nozzle.

About 2 years ago, we had the TFT rep out for a demonstration on the (then) new BlitzFire, as well as the 75psi hi-rise nozzles. Long story short, we had him teest ALL of our nozzles, including some that were 15+ years old. All but a couple of the old ones flowed per spec. The ones that didnt, he took with him for repair.

When he returned, he explained to us that the nozzles had simply been "dirty". Submerging them in warm soapy water and flushing them once a month like we had been doing didnt cut it. He then demonstrated how to properly clean and oil them. On top of that, he gave us a couple cleaning kits at no charge.

Since then, no problems with the TFT's

15. Akron salesman came and told us how much better his nozzles would be than our TFT's. Set up his flowmeter, ran a few of our setups, our 10+ year old TFT's performed exactly as they were supposed to. He ended up claiming his flow meter was bad.

The Akrons were nice nozzles, just wasn't thrilled with the salesman.

16. Bones and Dave....Glad to see the snow jobs the Akron and Elkhart sales people laid on you did not stick....

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