## GPM VS. PSI FOR A GIVEN PIPE DIAMETER

## GPM VS. PSI FOR A GIVEN PIPE DIAMETER

(OP)

Let me start by saying I don't know anything about fluid mechanics. I need to know how many GPM I can push thru a 2" pipe at 100 PSI. Assuming a length of 10 ft. And what would be the velocity. Seems like it would be a simple calculation. Can someone give me a formula?

Thanks

Chuck

Thanks

Chuck

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

At 100 psi for 10 ft, you are off the chart on the high velocity end. Erosion issues, noise issues, i.e. major problems would be in store for you.

To get in the ball park of normalcy, use 0.1 to 10 psi/100 ft. For 2" the corresponding flow range would be about 10 to 115 gpm.

Good luck,

Latexman

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

GPM of what?

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

Chuck

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

"Crane Technical Paper No. 410 (TP-410) is the quintessential guide to understanding the flow of fluid through valves, pipes and fittings, enabling you to select the correct equipment for your piping system.

Originally developed in 1942, the latest edition of Crane TP-410 has been fully updated to reflect the latest knowledge and research in the fluid handling industry. The TP-410 has served as an indispensable technical resource for over 60 years to specifying engineers, designers and engineering students."

I've used it almost 34 years. I recommend it highly. I wish I had had it when in school. And, it's not expensive, $60.

Good luck,

Latexman

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

Good luck,

Latexman

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

http://www.eng-tips.com/viewthread.cfm?qid=276054

If you calculate the maximum velocity with Cranes, you will get a velocity around 20-25 ft/sec which equates to a flow of around 200-250 gpm.

Here is a link to a chart that supports this.

http://www.dakotasupplygroup.com/wp-content/upload...

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

.

You also have to deal with codes! For example, Civils frequently go into the 20-30 fps on water mains. As a mechanical, the plumbing code limits the velovity to 8 fps. I've had to explain to my civil counterpart why my branch line was bigger than his main. they were not impressed

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

With my application in mind, which book would do me more good? Cameron or Crane? Just looking for an opinion if you have one.

Or, with my application in mind, is there a simple formula?

Thanks

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

" I am given water from a 2" hose at 100 psi and I am trying to figure out how many GPM I am being supplied. From this 2" hose it branches off into several smaller drilled lines and eventually back into a 2" return hose."

This is a completely different problem than what first appeared in your 1st post. If I understand what you are describing, the water is to be forced through numerous small drilled lines and back to the return hose.

1. The water pipe IS NOT the bottleneck. The main pressure drop will be through the numerous orifices.

2. You do not have 100 psi to burn. There must be enough pressure available to return to the 2" return hose and back to the source.

3. Determine the pressure drop through the mold (psi vs. gpm. This must be done through field experiments). Leave enough return pressure so you will not cavitate your pump.

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

I was tasked with estimating water supply for a mid-rise, no FP, that was a differned tap. My calculations showed a 14" line, was able to "justify" a 12" in my estimates. The main was 12". I was told that the city water mains are allowed to go to higher velocities since they are buried (noise not an issue). I ended requesteing two 6" tap offs closer capacity to the 14", put the civil was not happy. What AWWA standard do the mains fall under?

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

Good luck,

Latexman

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

Chuck

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

Yes.

Yes.

You also may need to understand "manifolds", "distribution header", "maldistribution", "series flow resistance", and "parallel flow resistance", because it is more complex than either reference mentioned above gets into. You've also got a ways to go before you are ready to do this. It is not beyond you, IMO, but if time is critical and you have the budget, you may want to sub this out to an Engineering Firm.

Good luck,

Latexman

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

Chuck

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

Your question seems to be how much capacity does a hose carry, not a piping question. Ask your rep at Grainger to tell you the answer.

Note that you may need to use multiple hoses as well to obtain the flow rate that you desire.

Note, you will get less flow out of a hose because the hoses may be corragated with poorer hydraulic parameters than pipe.

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

A fluid mechanics degree wouldn't help either; it's not what it sounds like.

This is advanced engineered plumbing.

Buy the Crane book; it's not expensive. Don't lend it out; it has a habit of not coming back.

There's an Imperial version and a Metric version; buy whichever one suits you.

The book will eventually yield to study, and will give you techniques for estimating the pressure drop from end to end of one pipe.

Multiple pipes in parallel or series can be estimated using Kirchoff's Laws, which come from electrical engineering but work just fine for fluids, except that fluid resistors are square-law devices.

If you're using a centrifugal pump, you can't just pick a flow number out of a catalog.

You have to model the entire system for a guesstimated but completely arbitrary flow. Once you have a pressure drop for that arbitrary flow, you can use it to compute what is effectively a Cv, then use the Cv to plot the system resistance curve, and graphically find where the pump curve intersects it, which is the operating point for the pump. You can do a lot of it in Excel. The fancy tools just make a solution quicker.

Luckily for you, the typical mold cooling system is normally bled of air, so you won't have to worry about two-phase flow. Not so lucky for you, the typical mold cooling system has a fairly complex internal geometry. You can model it as a combination of orifices and pipes, but when you test your model against a real mold, it won't be super-accurate. I.e., you'll be doing well to get within a factor of 2 either way. Luckily for you, centrifugal pumps are not super fussy about that.

First buy the book, find the examples that apply to you, and work them.

Mike Halloran

Pembroke Pines, FL, USA

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

On the complex components, like the plastic injection mold, you may need to drill down into the company that furnished it to find the one Engineer that designed/knows it. He/she will probably know how to characterize the resistance to flow, whether it's a K value or Cv value or two K or three K or equivalent length or whatever. If not, you may have to do some flow tests in the field. If so, yeeeehaaaa! You'll really learn something then.

Also, learn to use Search (between Forum and FAQs) to find old threads on the subjects and keywords you need. It takes time, but it's a gold mine!

Good luck,

Latexman

## RE: GPM VS. PSI FOR A GIVEN PIPE DIAMETER

thoroughlyover a few weeks would probably give you most of the required knowledge that you would get in a college course. But you might still be lacking the on-the-job learning and experience that would be required to tackle a real-world problem like this.One of the biggest conceptual hurdles to overcome it to understand the difference between pressure and pressure drop. Almost all engineers who have worked in fluid mechanics for a few years have this understanding so deep in their psyche that they cannot believe that it is not obvious to everyone. But it is not obvious.

The 100 psi you have is NOT all available to drive the flow through the 10 ft of hose. Part of that 100 psi will be used up overcoming friction in the hose, but some also has to be used to drive the water through your molds and through the return piping. There are techniques in Crane and Cameron for modeling these sequential resistances to flow. A resistance coefficient (usually just called the K value) has to be determined for each section, and for series flow the K values are additive. This is analogous to resistances in an electrical circuit (but more complicated).

If you can measure the pressures at the start and end of your 10 ft of 2" hose then you can calculate the

pressure dropacross the hose. And once you have the pressure drop you can calculate the flow rate. At 200 gpm the pressure drop would only be 5 or 6 psi across this short piece of hose. Fortunately conservation of mass means that if it is flowing through the hose then the same quantity is flowing through your mold. This means that you can calculate the flow through any section of the circuit for which you have the required information, or as a worst case you have to work with the K value for each element and the overall pressure drop.Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"