OT (sorta) - Pump Specification and Sizing

robertmee · Feb 25, 2009

Okay, I'll be the first to admit I'm a dufus when it comes to fluid mechanics. I have a small job that pays nothing (don't you love those) that involves moving two fluid ingredients from two storage tanks to a mixing tank. The design parameters are 6000 gallon mix, need to fill within 180 minutes (40 GPM or so). They plan on using 2" PVC. Control valve on suction side of pump to prevent blow by. Storage tanks apx 15' tall and 9' diameter (to calculate head pressure if needed).

Basically looking for a simple pump to deliver the material. The fluid is a 40% suspended solid so the issue is leaving the pipes full of material. We're having to pump from the discharge of the storage tanks, over about 15' then up about 10' and into the mixer. The plan is to reverse the pump and clean the line back into the storage tank after each pull (against the head pressure of the fluid in the tank). If the fluid is left in the pipes, over time, evaporation will leave a salty mess. There is a plan to include a city water cleanout for flushing during extended periods and shutdown.

Anyway, just wanted to get an idea for an application like this should I be looking at positive displacement, centrifical, stroke, etc. style pump and is the sch 80 PVC they are planning on using sufficient to withstand the PSI needed to pump the material at 40 GPM.

Alternatively, if there is a good website that does these type calculations, please point me in that direction.

Thanks!

PS....Part II. Also, is there a simple manual (electrically powered not pneumatic) gas pump type system for unloading the mixer into 55 gallon drums. Fill rate needs to be 5 GPM.

Ken Moore · Feb 26, 2009

Well....
Since you want to reverse the pump, I think you are going to need a positive displacement pump. One thing you did not mention was pipe size and viscosity of the material. If you use a PD (positive Displacement) pump, you are going to have to ensure you have an open path before starting the pump, so your valves are going to need limit switches. You will also need relief valves to protect the piping from over pressure. Most pump vendors will help you with the sizing and pump selection.

An alternative might be a pneumatic diaphragm pump, the discharge pressure will always be limited by the air supply pressure, which you can regulate. The pumps do not "reverse" , but you can pipe them with the correct valving and reverse the inlet and outlet lines, we do it all the time. Another advantage of a pneumatic pump is cost, you didn't mention if the pump had to be stainless or carbon, or bronze etc... However, since you are using PVC piping, you could get a plastic pump as well.

Do you have the air supply needed to run a pneumatic pump?

Tom Jenkins · Feb 26, 2009

Pipe schedule is determined by pressure only, not flow rate. You need to get the rated pressure for the pipe diameter and fluid temperature you are using and make sure your total pressure (static head plus friction losses) is less than that.

You want your velocity to be between 2 and 4 ft per second. At 40 gpm your velocity is going to be close to 4 ft per second, so a larger pipe may be called for.

robertmee · Feb 26, 2009

Thanks guys for the detailed information. Just to follow-up, and add some possible answers to the questions.

Right now, the pipe is spec'd at sch80 2". I know that's a case of the cart leading the horse, but we are late to the game (another integrator dropped the ball and was kicked to the curb).

The temperature of the material will be ******t. South Alabama in a warehouse so anywhere from say 40 to 100 deg F.

I was thinking probably a stainless pump, as the material salts and would want the strength of a stainless vane or impeller to 'crunch' through the residual material and wear wouldn't be as bad.

Viscosity should be close to H20.

Good call on the valve limit switch. Normally we always have those, but doesn't hurt to re-emphasize. Also good call on pressure relief pop-offs. Wouldn't want to rupture the PVC.

No, there is no compressed air available. This equipment is in a rental warehouse with 3phase 230V only.

leitmotif · Feb 26, 2009

robertmee said:
Okay, I'll be the first to admit I'm a dufus when it comes to fluid mechanics. I have a small job that pays nothing (don't you love those) that involves moving two fluid ingredients from two storage tanks to a mixing tank. The design parameters are 6000 gallon mix, need to fill within 180 minutes (40 GPM or so). They plan on using 2" PVC. Control valve on suction side of pump to prevent blow by. Storage tanks apx 15' tall and 9' diameter (to calculate head pressure if needed).

Basically looking for a simple pump to deliver the material. The fluid is a 40% suspended solid so the issue is leaving the pipes full of material. We're having to pump from the discharge of the storage tanks, over about 15' then up about 10' and into the mixer. The plan is to reverse the pump and clean the line back into the storage tank after each pull (against the head pressure of the fluid in the tank). If the fluid is left in the pipes, over time, evaporation will leave a salty mess. There is a plan to include a city water cleanout for flushing during extended periods and shutdown.

Anyway, just wanted to get an idea for an application like this should I be looking at positive displacement, centrifical, stroke, etc. style pump and is the sch 80 PVC they are planning on using sufficient to withstand the PSI needed to pump the material at 40 GPM.

Alternatively, if there is a good website that does these type calculations, please point me in that direction.

Thanks!

PS....Part II. Also, is there a simple manual (electrically powered not pneumatic) gas pump type system for unloading the mixer into 55 gallon drums. Fill rate needs to be 5 GPM.

Robert
Here is what I understand
1. You are combining Part A and Part B
2. Either or both are a salt and water(??) solution
3. You are ending up with a mix of part A and Part B with total volume of 6,000 gallon.

What is Part A What is Part B and what is solid content of each. What is the solvent (water or??)

Is flammability an issue??
Chemical Safety -- Are any of these materials reactive or poisonous etc etc? Environmental concerns?

How much of Part A and how much of Part B

If only one part has a solids content pump that first then use the other part to flush the line.

How are you measuring finshed solution component ratios?

The salts need more consideration. If highly abrasive then plastic would not be a good choice. Depending on what salt(s) you may need SS 316 or maybe monel.

The process in Part II needs a lot more explanation.

Dan Bentler

Ken Moore · Feb 26, 2009

Good point, generally speaking, stainless does not hold up well when chlorides are involved.
Bronze may be a better option. Monel would work, but is costly.

robertmee · Feb 26, 2009

leitmotif said:
Robert
Here is what I understand
1. You are combining Part A and Part B
2. Either or both are a salt and water(??) solution
3. You are ending up with a mix of part A and Part B with total volume of 6,000 gallon.

Correct...I was not given the exact chemical composition (somewhat proprietary), but was told that each constituent was a 40% soluble solution, each subject to evaporation and leaving a crusty salt residue over time. I'm trying to get more info.

Is flammability an issue??
Chemical Safety -- Are any of these materials reactive or poisonous etc etc? Environmental concerns?

Flammability, explosiveness and chemical safety are not of a concern according to the permits. The tanks are vented to atmosphere and the material is non-corrosive.

How much of Part A and how much of Part B

Roughly 40-60

If only one part has a solids content pump that first then use the other part to flush the line.

Both have solids.

How are you measuring finshed solution component ratios?

The mixing tank is on load cells.

The salts need more consideration. If highly abrasive then plastic would not be a good choice. Depending on what salt(s) you may need SS 316 or maybe monel.

I was thinking SS. Not familiar with monel, but will research.

The process in Part II needs a lot more explanation.

The 6000 gallon mixer that's on load cells has a 2" discharge at the bottom. The tank is pitched forward so that it pretty much would empty by gravity. Once A+B are measured and mixed, the customer wants to fill 55 gallon drums with what he described as something similar to a gas station pump handle. Something with variable flow control that 'pumps' when the handle is pulled. I know gas stations use a recirculation style setup with a proportioning valve controlled by the handle, so it may be something like this, or anything else that someone has knowledge of or experience with.

Thanks again for the insight and help. I know it is frustrating not having more information, and I'm trying to get more as we speak. But it is a pretty fly by the seat of your pants operation.

OT (sorta) - Pump Specification and Sizing

robertmee

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Ken Moore

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Tom Jenkins

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robertmee

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leitmotif

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Ken Moore

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robertmee

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