Dual Pumping Operations -outdated?

[RFDACM02]

I'm not sure that running water through a non-operating pump is exactly "dual pumping," but I'll try to answer your question (I'm sure someone will correct me if I botch it).

I wasn't calling it dual pumping at all, just wanted to know "what if". I was think if you were correctly dual pumping then the first pump died. Which you answered perfectly!

[Catch22]

I wasn't calling it dual pumping at all, just wanted to know "what if". I was think if you were correctly dual pumping then the first pump died. Which you answered perfectly!

OK, I misunderstood what you were asking. But if you got the answer you were looking for, it's all good.

[HotTrotter]

[QUOTE=RFDACM02;808581]Come on, you don't really expect that we'll beleive you only have some much room in your brain? If you learn something you have to forget something else? I realize tandem pumping might be a stretch for most of us, but nowadays so many firefighters only know how to throttle up until the needle is pointing at the tape! So little understanding of why you can't draft over 22 ft. or that all pressures are equal in a closed system! I don't beleive it can hurt to teach and practice these evolutions as long as you can keep up with the rest which may be the real challenge.{/QUOTE]

The human brain can only hold and comprehend a finite amount of information. This is why not all people can be engineers, scientists, doctors, lawyers, etc. The total lift that you can draft is limited by atmospheric pressure. Using approximate values of 15 psi Atmosperic and a loss of 5 psi per 10 foot of lift you will see that the amout you can draft is closer to 30. In a closed system with no water flowing the pressures will without a doubt be equal. If you are flowing water the pressures will vary, as will the velocity.

I think HWOODS describes the perfect scenario of why some depts wouldn't waste money on a pump over 1000 gpm. I'd agree individual mains or grids are a better choice, but it depends on hydrant spacing and flow. We have a few places where tandem pumping would be a benefit, though I'd probably opt to just stretch a 5" LDH from the original engine. You do understand that the GPM rating of your pump is meaningless on a big hydrant if you have adequate discharges right? You can use a 1000 gpm pump as a 2500 gpm water manifold. We've flowed around 3000 gpm using a 1500 gpm pump off one of better hyrdants.

WASTE (!! ) money on a 1000 gpm pump. I would say you are crazy to buy anything less than a 1000 gpm. We put 1500 gpm pumps in all of our newer trucks, 1990 and later. Are you worried about the extra weight? And if it is cost, then how do you justify a tandem pumper (an entirely second truck) vs one truck with a bigger pump? The only time I have seen a pump not work is when they freeze up in winter. In that case it would be better to push all of the water through a single pump rather than two pumps. The faste the water flows the less the liklihood anything will freeze.

Again, not a high priority in most places but a valid technique that may be of value at some point. I still am not sure why supplying the 5" LDH is not a better option? It seems easier and faster.

I agree 100% here. Most hydrants in our area will only supply a max of 1500 gpm. And there are many that struggle to get 500 gpm. If I try to hook up to two hydrant on the same line my trucks will be fighting for water, they in essence would split the available supply, with the upstream truck getting more of the water. And I oculd even connect to multiple hydrants on different parts of the same grid and still not be able to pump at full capacity.

I know of an incident recently where there was a used tire processing facilty that burned. They shredded up old tires for use in other things. Anyway, the local departmetn had their Quint hooked up with it's 2000 gpm pump, and they were feeding it from anohter pump. The gauge on the quint said they were flowing 3500 gpm. Makes you wonder how that is possible. ??

[RFDACM02]

WASTE (!! ) money on a 1000 gpm pump. I would say you are crazy to buy anything less than a 1000 gpm.

I said HWOODS presented a perfect example of why a dept. would not waste money on a pump greater the 1000 gpm. I think most everyone agree a 1000 gpm is about the minimum. I have a hard time justifying buying a pump over 1250 in my department. Given the hydrant flows average around 1000 gpm and drafting is just about non-existant, we don't need the extra gpm pump at the cost of a larger engine, transmission, dual hard sleeves, etc. Our new engine will have plenty of discharges for those few exceptional hydrants, but the higher GPM just isn't required. Anyway, I'm sticking to my point that I'd like my people to know more, not less when it comes to this job. I'll take my chances with what they'll forget, we do have some control over what is important and routinely practiced.

[Rescue101]

Trotter,let me simplify your pump dilema a bit.750-1250 pump same impellers,same casting.1500-2000 same impellers same casting.The part that determines whether it's a 750 or a 1250 is the discharges.Same with the big pump.That's oversimplification at it's finest but basically correct.Now as Harve indicated to you earlier the wild card is the hydrant.Catch a good one and that 'lil ol' 1000 can flow half again or even double it's at draft capacity.People make waaaay too much complication in Fire service hydraulics.A wise old fire instructor once told me,"better to figure your FL high and have plenty of water,than figure it low and run out".As far as your little hard drive having space,remember simple formulas that work at high noon or 0 dark thirty.I've used three friction loss formulas for years.30#per 100' small hose,15#100big hose,5#100LDH.Not accurate with todays hose construction but the old Fire instructor was right. T.C.

[Bones42]

Anyway, the local departmetn had their Quint hooked up with it's 2000 gpm pump, and they were feeding it from anohter pump. The gauge on the quint said they were flowing 3500 gpm. Makes you wonder how that is possible. ??

Quint - 2000gpm. Other pump - 1500gpm. What's the problem?

[JohnVBFD]

Quint - 2000gpm. Other pump - 1500gpm. What's the problem?

It requires thought, thinking and logic to be able to comprehend math.

[JohnVBFD]

Trotter,let me simplify your pump dilema a bit.750-1250 pump same impellers,same casting.1500-2000 same impellers same casting.The part that determines whether it's a 750 or a 1250 is the discharges.Same with the big pump.That's oversimplification at it's finest but basically correct.Now as Harve indicated to you earlier the wild card is the hydrant.Catch a good one and that 'lil ol' 1000 can flow half again or even double it's at draft capacity.People make waaaay too much complication in Fire service hydraulics.A wise old fire instructor once told me,"better to figure your FL high and have plenty of water,than figure it low and run out".As far as your little hard drive having space,remember simple formulas that work at high noon or 0 dark thirty.I've used three friction loss formulas for years.30#per 100' small hose,15#100big hose,5#100LDH.Not accurate with todays hose construction but the old Fire instructor was right. T.C.

Please myself and plisken I believe already went over pump basics with him once. We were wrong he was right.

I will go out on a limb here and say, you are wrong he is right.

[Catch22]

Trotter,let me simplify your pump dilema a bit.750-1250 pump same impellers,same casting.1500-2000 same impellers same casting.The part that determines whether it's a 750 or a 1250 is the discharges.Same with the big pump.That's oversimplification at it's finest but basically correct.Now as Harve indicated to you earlier the wild card is the hydrant.Catch a good one and that 'lil ol' 1000 can flow half again or even double it's at draft capacity.People make waaaay too much complication in Fire service hydraulics.A wise old fire instructor once told me,"better to figure your FL high and have plenty of water,than figure it low and run out".As far as your little hard drive having space,remember simple formulas that work at high noon or 0 dark thirty.I've used three friction loss formulas for years.30#per 100' small hose,15#100big hose,5#100LDH.Not accurate with todays hose construction but the old Fire instructor was right. T.C.

I thought that the impellors were different with each size pump. While they have the same castings, it requires a larger impellor as well as the discharges to push the rated GPM (so I've always been told).

[Rescue101]

Catch,Did you catch the standard disclaimer"oversimplifcation"?.You're correct,but different pump mgfs do different things to get the different gallonages.Subtle changes like impeller size or merely "detuning"the bigger ones to accomplish the same end result. Most of my pump universe centers around Hale and those are a "derated" pump.Doc,me wrong? I won't have any feelings left,you guys keep beating me up. Yeah,I went a little overboard but some of these guys make too much work out of some simple hydraulics.One thing I'm pretty sure I'm not wrong on is that some in this post don't know the difference between Dual pumping and RELAY pumping.I'm reasonably sure those two animals have different spots.It's been entertaining though. T.C.

[hwoods]

Catch,Did you catch the standard disclaimer"oversimplifcation"?. Yeah,I went a little overboard but some of these guys make too much work out of some simple hydraulics.

WHAT HE SAID!!.....

[Catch22]

Catch,Did you catch the standard disclaimer"oversimplifcation"?.You're correct,but different pump mgfs do different things to get the different gallonages.Subtle changes like impeller size or merely "detuning"the bigger ones to accomplish the same end result. Most of my pump universe centers around Hale and those are a "derated" pump.

Actually, I caught it, just missed the context. My apologies.