Beginner - best piping for most flow - 2" pvc

[mrwoojoo]

Hello.

I have used these forums many times to get answers, but have had a hard time finding someone to talk to or find relevant threads with this answer, although I am sure it is pretty basic.

I have to redesign/plumb a fertilization/acid injection line where I work (greenhouse). I will describe what is in place and what I wish to achieve and I desire someone who understands this to simply give me a heads up on which is more efficient at delivering the most water/pressure at hose end.

Currently, I have a water source from 2 wells, with primary well providing 66 gpm @ 45-65psi, and a secondary well providing 60 gpm @ 40-60 psi. The secondary well supplements the primary well on heavy watering days, which is only very occasional. It uses a pressure differential valve, I believe known as a 'clay' valve.

My water source then is piped into 4" sch 40 pvc, which is ran to a couple different injection sites. The site I am about to redisgn looks like this

|
___{}____{}____________________| 3" line
4" | 2" line
----- |
|___{}____{}____________________
2" line | 3" line
|


Where the {} is a chemical injector, which is limited to 1.25" connection and imposes approximately 12 psi loss @ 35 gpm.

This system injects sulfuric acid via the first injector and fertilizer via the second injector. After injection, each 2" line then empties into a 3" line, which in turn routes to different greenhouses for use in watering.

I have been updating our water techniques to include the use of more in-line probes and electronic injection with LMI chemical metering pumps. This allows me to write software for use with a DAQ device and grab output signals from electric pump controllers and probes to log what is happening to the quality of the water.

In changing the acid injection from water driven injection to electronic injection, manifolds for flow sensors and manifolds for probes increase the length of pipe needed in the design, not to mention valves, untions, static mixers, etc.

The problem arises because, if you note on the rude schematic above, that while each 2" line feeds a segment of 3" line, the balance of each 3" line is unequal in usage. Tht is to say, that one 3" line supplies 3x the amount of greenhouses as the other 3" line, leading to loss of flow/pressure at hose end. On very hot days our primary well cannot provide the demand, and the secondary well releases some to supplement, although in a few weeks we will be placing a frequency drive pump in the primary well that should alleviate that issue.

I aim to increase the overall flow in the 3" lines by having both 2" lines feed into the 3" lines, tie them together.

The new design calls for 2 water driven injectors for use with the fertilizer, and there is not a product that is affordable or offers relative complex free usage to replace these, unfortunately. So I need to know, which scenario below will give the most flow/pressure at hose end.

Design 1:
Each 2" line, coming from the 4" main, will pass through a single water driven injector (losing <= 12 psi) and then connect to the 3" line. The 3" line is no longer segregated as two seperate lines, but exists as one 3" line.

Design 2:
Each 2" line, coming from the 4" main, will pass through a single water driven injector (losing <= 12 psi) and then the output of these injectors will be tied together, so that one 2" line is connected to the 3" line.

Design 3:
One 2" line, coming from the 4" main, will pass through two water driven injectors, running in parallel, where the output of the injectors will join again into one 2" line, which then connects to the 3" line.

The injectors are Dosmatic A40, max 40gpm. They tell me that running these in parallel should provide a single 2" line to have a max flow then of 80gpm. My question comes up because I have the ability to design this in multiple configurations, and do not understand which method will provide the best performance.

I have contacted numerous people, from well pump to plumbers to boiler contractors to the injection manufacturers. I have recieved different answers from all of them, thus leaving me in an even more confused state. And it may be that there is not any one answer. But I would like to understand this a little bit so that on future upgrades I can design the most efficient system possible. Water is king in this business.

Thanks to anyone who might take the time to look and reply to this.

Mr Waltman.

 

[BigInch]

Maybe this helps,

http://www.pipeflowcalculations.com/pressuredrop/index.htm

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[cvg]

80 gpm is pushing the limits for a 2 inch line. Why are you insisting on running the entire flow through one 2" and then splitting it off two ways in a 3" line? Stick with option 1 but upsize the pipe coming out of the dosing manifold to 3 inch.

 

[mrwoojoo]

Thanks for replying.

I guess I am not insisting on anything really.

The 'recomended' configuration for higher flows form the dosing manufacturer is to run 2 injectors in parallel from one 2" line, with the exit point as a 2" line.

My existing 3" distribution line is in 2 segments, for simplicity one going east, one west. The current layout with one injector feeding the east line, one injector feeding the west line, via 2" pipe.

My goal, to connect the 3" east and west lines to create one large line. The best solution, to plumb the injector lines into the 3" line to provide the most flow/psi.

The options:
1. One 2" line into 2 injectors (parallel), one 2" line outgoing to 3" line

2. Two 2" lines, each into an injector, one 2" line coming out of injectors (parallel still, but seperate feeds) to the 3" line

3. Two 2" lines, each to an injector, two 2" lines, both feeding back into 3" line

Lacking education on such things, I can only draw on what experience I have. It would SEEM that Two 2" lines feeding the 3" line would be best, but having read what the manufacturer stated and some other articles, I am wondering if it is more efficient to run them in parallel and if such things as having the 2" pipe running at or near it's total capacity would feed the 3" better than two 2" pipes that each lose energy to the injectors. It is somewhat confusing, knowing whether a parallel setup will actually lose more or less energy than a side by side setup, let alone whether a lower flow/psi in a pipe is better than a fuller flow to get the best performance.

Please forgive the ignorance. Any further advice (and maybe a short explanation so I can understand 'why') is greatly appreciated.

 

[cvg]

higher flow velocity through a smaller pipe will result in increased pressure drop. You stated that you are experiencing low pressures at the end of the run. Upsizing the pipe and feeding from both injectors will help. However, this is just a recommendation because you have not given enough information to analyze it properly. You can do option 3, but you really need to connect the 3" line as you indicated in option 1.

Design 1:
Each 2" line, coming from the 4" main, will pass through a single water driven injector (losing <= 12 psi) and then connect to the 3" line. The 3" line is no longer segregated as two seperate lines, but exists as one 3" line.

 

[StoneCold]

mrwoojoo
If this was mine I would install a flow meter in a four inch line and use the flow meter to control the injection rates of the acid and the fertilizer with the help of a small PLC or Dosing controller from Walchem. Then you recover the 12 psi you are loosing in the 2" dosing injectors.

Regards
StoneCold

 

[robs68charger]

As Stonecold suggested using a flowmeter can be good. As also stated using an LMI metering pump, say a 7 series, can accept the pulses from the flowmeter and inject your acid and fertilizer as you decide. This also allows for the lack of reducing down for you injectors and no 12 psi pressure drop. The injection pumps uses 1/2" not threads so you would just need to install a tee and reducing bushing for your injectors. This option also allows for the option of recording how much of what was injected.
-Rob

 

[mrwoojoo]

Very Nice place here.

I must add some more info as I was not expecting much input in way of dosing.

I do indeed have LMI pumps, thus the whole reason for redesigning the system. In the past, I cut 93% sulfuric acid to about 3-6% to use in the dosmatic injectors. A few years ago I switched one injection site over to LMI 7 series with seametric flow meter/controller. Now I mix up a 20-30% solution, a little longer to mix due to heat, but lasts a lot longer, which was the goal. Due to the nature of watering in a mountain state climate, I have a large range of flow varying day to day, month to month. I originally had invested in LMI pumps for both the acid injection as well as the fertilizer injection.

However, in examining the needs for the fertilizer, short of some rather complicated components, it cannot be done easily. This is due to the fact that one pump would be needed for the very low flow states and one for the high flow. So the end result was that I had to settle for electronic injection for acid, and still have to use the dosmatic for fertilizer.

I do indeed log the 4-20ma signal to a DAQ. Actually my inline ph/ec/flow meters/probes are all sending a signal via cat5e to a server with the DAQ, and I have programmed a VB6 app that monitors them and logs/averages them, letting me see history or real time what is happening.

I use what is called 'remote injection' with the dosmatics (it is an attachement) so it is not putting chemical in the top part of the dosmatic but only in the line. I have been using TAH 2" Inline Static Mixers as well to get everything as blended as possible.

So in this case, I am plumbing it up for use with the LMI pumps for the acid, and restructuring the pipes so that I can merge the seperate 3" lines into one line, while also trying to get the best flow through 2 seperate injection lines into that single 3" line.

I am more than happy to supply much more information than this, pictures or whatever. It is somewhat hard to find good information (other than white papers) on this sort of thing. I have been shooting from the hip mostly, finding as I go what is more effective etc.

Thanks to everyone so far, this is great to have such great ideas.

 

[eadwine]

Why not combine your different injection points to one location, run the 4" line to the 3" branches and reduce down to the 3" branches with a reducer & tee. As for the mixing at the injection points in the 4" line, install a static mixer just downstream of the injection points.

This will give minimal pressure drop within the system by eliminating the 2" reductions. Which was probably installed to increase line velocities and turbulence for mixing purposes.

 

[mrwoojoo]

I would actually love to run the 4" to 3" branches as you suggest. I cannot however, due to the fluctuation of water usage. The injectors I am using (dosmatic) do come in larger diameter sizes, and utilize a rotary design (nice) however my flow cannot be the minimum required much of the time. That would have been a nice solution.

Indeed because for this chemical is concentrated fertilizer, I am bound by the laws of solubility as to how concentrated I can mix it. Unfortunately 300:1 is about the max I can do this before calcium starts to precipitate in the solution tank. (which requires some rather large electronic injectors) Due to the fluctuation of > 60gpm to < 5gpm at certain times of the year, no one pump (that I have found) seems to properly provide a cost effective solution. A hybrid combination pump system I was thinking of approaching, but the technical nature of such a beast (though not beyond me) is something we were not prepared to do right now.

I do have some LMI pumps injecting sulfuric acid (electronic), which is at approx 30% reduced from 97%. This, as you suggest, could easily be accomplished with a simple 3 or 4" tee for the injection point.

I do have a static inline mixer (actually 2 - one in each 2" line).

It is the contraints of the chemical injectors for the fertilizer that binds me to 2" pvc. I have about finished the job, and what I did was to put some TrueUnion valves in place (among other tedious routing) so that I can try 4 different paths of water flow to find what provides the best overall rate. More unions and valves than were actually needed, but without a proper diagnosis of which method of pipong would provide best results, and with such wide variances in the expected flow rate, the money will be well spent in the end to physically see which configuration is best.

Thank you for the input, I appreciate it.