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Product distribution - Tubing Lines

Product distribution - Tubing Lines

Product distribution - Tubing Lines

Hello everyone,

I am a junior engineer. I am now working on the design of a dosing system for small quantities using tubing lines and very specific equipment (flowmeters, valves...).

Due to the low flow and configuration (30m length - 10 m up), the pressure drop that I calculate will be of aprox. 6 bars (considering the flow meter pressure drop).

My question is: With an adequate pump (6bar+)... do you think this installation could work?

I am not familiar with tubing (I always work with pipes). I know this is a very general (and silly) question but I have the feeling I am missing something.
Tubing lines are can withstand very high pressures, so I assume they are normally used on high pressurized systems.
The product is no viscuous and has a density of 850kg/m3.

Thank you very much for your support.

RE: Product distribution - Tubing Lines

As the material is suitable for the pressure and temperature per your system, tubing is as good as piping for carrying fluids from point A to B. Assuming that the pump pressure head calculation of 6+ bar includes the extra head for contingency.

RE: Product distribution - Tubing Lines

We make a lot of small diameter stainless steel tubing, both seamless and welded and cold drawn.
People are usually surprised when they find out that 1/4" x 0.022" and 3/8" x 0.035" have a working rating of over 3600psi.

Many dosing systems do not use valves and flow meters, but rather close-loop controlled metering pumps. Look at your system options.

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P.E. Metallurgy, Plymouth Tube

RE: Product distribution - Tubing Lines

Thank you very much for your answers. It is great to have experts' feedback :).

In my case I am surprised for the low pressure drop, seeing that tubing lines have such a high pressure rating.

I checked some metering pumps but the accuracy is not as good a coriolis flowmeter.

Thanks again!

RE: Product distribution - Tubing Lines

You didn't check the right pumps then.
I think of people like ProMinent, Lewa, and mRoy.
These pumps have better turn-down ratios than coriolis meters, usually 1000:1 with constant accuracy.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Product distribution - Tubing Lines

In our system we would need to be able to select the destination as well as the amount of raw material to load (based on a recipe in mass).

I have been checking some from Prominent and Lewa pumps and accuracies are aprox 1%... with the accuracy of our selected flowmeter is 0.3%.
Even though our application is in production (not labo), the quantities used are very low (from 150g) and small deviations could have a significant effect on the final product.

I will continue checking, it is worth having a look.
Thanks a lot for your advise.

RE: Product distribution - Tubing Lines

If you want recipe dosing of specific quantities of material, using a pump and a flowmeter is the wrong way to do it.

What you really want is a syringe pump:


Pressure drop is a matter of flow, density and linesize. If the pressure drop is too high, you simply increase the linesize, the same as you would in piping. The difference is that the surface area to volume ratio is very small- you will find it difficult to achieve high Reynolds numbers in these lines, so the velocity "rules of thumb" used for pipe sizing go into the toilet as useless once you're into tubing. Instead, you use a parameter such as differential pressure per 100 ft of line length etc.

RE: Product distribution - Tubing Lines

Thanks again Moltenmetal.
I think those types of pumps cannot be an option on our case. They are difficult to operate with and we need a complete close system.

I have one more little question... I have to select the tubbing size for the system and due to the low flow I also have low flow velocities (0.6m/s or 0.3m/s).. could that be a problem also considering the distribution circuit(30m length - 10 m up)? (of course, also considering enough pump pressure)

Thanks again.

RE: Product distribution - Tubing Lines

Regarding the velocity question -
Will laminar flow be an issue for your liquid or transport dynamics (as moltenmetal pointed out)? If some residual liquid remains stagnant for a period of time, is that okay or do you need to provide low point drains and purge gas?

RE: Product distribution - Tubing Lines

You have to also consider how you will prime your tubing and keep it primed. Temperature changes will cause volume changes in long lengths of tubing. Liquid expansion is greater than metal expansion.

You need a flow loop for the long lengths of tubing so that the line is always filled up to the point of use and constantly flushed to remove bubbles. At the point of use you place the metering pump. And right at the injection point you place a check valve to prevent dribbling flow after the metering pump has stopped.


RE: Product distribution - Tubing Lines

A syringe pump is about the easiest pump to operate that there is, if your application is batch dosing. It is far simpler, and more accurate, than any combination of pump and flowmeter you would ever put into a batch dosing application that requires any kind of accuracy/precision.

Low flowrates result in low velocities. Low velocities are not a problem as long as you are not trying to suspend particles in a liquid, i.e. pumping a fast-settling slury.

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