Change water DIY Cole-Parmer Heads

[bulabr]

Hi friends,

Please I have a question about my new set up to Change Water(CW).

I have two heads from Cole-Parmer L/S 13 and a Pittman GM9236E815 24v Gearmotor. I set up the two heads in series (2 channels) and the hose is made of silicone and the source is 10VDC, 1A as the pictures.
The system is consuming 200mA.

My idea is to exchange 20 Gallons each 20 days, as my tank is 75G plus a sump of around 10G. After assembly everything, the set up worked very nice, but there is a little problem. The IN and OUT water is not in the same rate between the two heads. I have heard that these kinds of heads are extremally accurate, and now in the practice, I can not see that. Maybe I am asking for a lot, but in the two tests, the difference was around 100ml for each 12 hours. Meaning 200ml per day, meaning 4 liters in 20 days.

Do you know if there is a way to have the same amount rate in and out?

I have in the tank the top-off as well, RODI water as usual.

They will work in the same time, top-off and the CW.

I was imagining, I will have two scenarios.

Scenario 01, I set up the faster hose to put the new saltwater in the tank and the slower hose to take out the dirty saltwater and throw in the drain… I will have the top off working slowest, and in the final, I will increase the salinity of the tank.

or

Scenario 02, I set up the faster hose as the old saltwater in the drain and the slower hose for the new saltwater in the tank … I will have the top off working fastest, and in the final, I will decrease the salinity of the tank.



Please tell me if you have the same kind of set up, with Cole-Parmer heads, if you got the same rate between the two heads…

I just started the third test, after disassemble and assemble the system again

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20180522_123712.jpg


Am I so conservative about the precision?

Bulabr

[on the spot]

Originally Posted by bulabr

Do you know if there is a way to have the same amount rate in and out?

Am I so conservative about the precision?

The same heads spinning at the same rate suggest you have two different diameter hoses - so I'd start there. Inside diameter.

HTH

[Member No. 1]

Thing to remember is that most good quality dosing set-ups like a GHL, Apex DOS, Litermeter III all have the ability to be "calibrated". Yours does not.
I'm sure the heads you have are accurate, but just like a pH probe, it needs a standard to be set to, and once set will be right.

Another way to look at it...
2 cars, side by side driving down the highway, both speedometers reading 55 mph. Even though they both are reading the same 55 mph, if the speedometers weren't calibrated to each other or a set standard, one car could be going faster than the other. Which is what's happening in your case.

Take the DOS for example, during calibration, you calibrate it to the amount it pumps in a minute. This should be 40ml. Once you start the calibration, it auto stops. Then you input the amount that it actually dosed, say 38ml. Then the DOS knows that with "X" revolutions over "Y" time, "Z" amount was dispensed, and through the software makes the required adjustments.

I use a DOS for daily water change of 9.6 liters, using both heads, and it's spot on.

[bulabr]

The hose was bought in one single piece(length), I just cut in the middle and supposed to have to be the same diameter as a whole. I gonna do this kind of test, based in the good suggestion from HTH. I will do the test as head 01 with the hose 01...and the head 02 with the hose 02. After I will exchange the hose settting up the head 01 with the hose 02, and head 02 with the hose 01...and I will test again. If the result is the same, the heads are not good(difficult to happen in my opinion). if the result is different, the hose has problem(more probable). The tests have been done with more than 8 hours to get better results. As you said Pete, for this kind of set up, I can not control the heads indepedently. This kind of product is used to dose medication in the patients, as I know...then the accuracy of the heads should be extremelly high.

Bulabr

[Member No. 1]

Originally Posted by bulabr

SNIP--->This kind of product is used to dose medication in the patients, as I know...then the accuracy of the heads should be extremely high.

Bulabr

I have no doubt they are, but even the best most expensive piece of equipment needs to be calibrated out of the box.

I'd be surprised if you ever get the 2 to dose the exact same amount. Even as you have them linked together.

[bulabr]

Originally Posted by Member No. 1

I have no doubt they are, but even the best most expensive piece of equipment needs to be calibrated out of the box.

I'd be surprised if you ever get the 2 to dose the exact same amount. Even as you have them linked together.

I agree with you Pete, but how to calibrate those guys????

[jimmyj7090]

I wonder if the tubing is not playing nice with the pump heads leading to the inconsistency? The proper masterflex tubing is very different from cheaper silicone tubing. The silicone tube could be pinched, twisted, not flexing around the rolloers properly, or otherwise malfunctioning.

I have a dual head cole parmer set up and it is very consistent with the proper tubing.

[bulabr]

I can say for sure that the tubing is very well set up in the internal cavity(not pinched or flexing around the rollers), but I agree that the silicone tube which I bought is not very trustfull. The tube is...Size：ID 0.8mm±0.2mm, OD 4.0mm±0.2mm. Whats your heads Jimmyj7090? Is it for L/S13 as well?

[jimmyj7090]

Originally Posted by bulabr

I can say for sure that the tubing is very well set up in the internal cavity(not pinched or flexing around the rollers), but I agree that the silicone tube which I bought is not very trustfull. The tube is...Size：ID 0.8mm±0.2mm, OD 4.0mm±0.2mm. Whats your heads Jimmyj7090? Is it for L/S13 as well?

I'll have to look when I get home later. I don't doubt that you installed the tubing correctly, but I do know that the masterflex tubing is very much different in many qualities than the silicone tubing I once ordered to try to save $ on as a replacement.

[Member No. 1]

Originally Posted by bulabr

I agree with you Pete, but how to calibrate those guys????

You really can't. Dosing units use software to adjust for calibration.
I have 3 Apex DOS units. All required calibration out of the box. They even come with a graduated cylinder just for that purpose.
During the calibration, it fills the cylinder over a given time frame, then stops. It should be a 40ml. If not, then you input the amount that was dispensed. The Apex then adjusts for the difference. I have seen them anywhere from 38ml to 43ml prior to calibration.
But after calibration, all 6 heads are spot on.

From the manual for the DOS. This helps explain.

Your DŌS pumps must be calibrated before using or it WILL NOT dispense an accurate amount of fluid. THIS
STEP IS IMPORTANT. The calibration is a simple process that is performed one pump at a time. You can
calibrate using the Display module or the classic Apex web pages. Calibration is the process of running a pump
for a fixed amount of time and confirming how much fluid it pumps using the graduated cylinder (included).
Put the in/suction tube into a glass of tap water. Put the out/discharge tube into an empty glass. Prime the
pump by pressing the button on the front of the DŌS that corresponds to the left or right pump and hold it until
all air bubbles are out of the tubing. Now put the discharge tube into the graduated cylinder and you can begin
the calibration.
From the Display module, navigate to Setup – Module Setup – Config Module or via the web pages navigate to
Configuration – Module Setup. Select your DŌS module. Then select the pump you want to calibrate. Pump
#1 is the left side pump, #2 is the right side pump. Then press ‘OK’. The pump will run for approximately 90
seconds then stop. After it stops, note how much water (mL) is in the graduated cylinder and enter that value.
There will be about 40 mL of liquid, maybe a little more or less but it’s that exact amount that becomes your
calibration.
When viewing the graduated cylinder, it’s important to view it directly level with the liquid level – don’t view at
an angle. Also, you will note that the liquid in the cylinder curves upward at the walls of
the cylinder. The bottom is called the “meniscus”. Your reading must be from the
meniscus. Precision is important here if you want accurate dosing so take some time and
repeat the calibration if necessary.
Repeat the process for the remaining pump. Your DŌS is now calibrated. Any time you
change the types of fluid you’re pumping, change your tubing orientation or replace your
pump tubing you should recalibrate.

[bulabr]

I made the test changing the hose as I mentioned.Yes...the problem is the hose as Pete said. the result was the opposite. I am thinking to buy another one from www.mcmaster.com now...

[on the spot]

Originally Posted by bulabr

I made the test changing the hose as I mentioned. Yes...the problem is the hose...

The more expensive accurate tubing will make the difference.

You won't need it for the entire run, just through the heads. You can join them with barb connectors -

HopeThatHelps

[bulabr]

Well... can I trust in McMaster products?

[slief]

The issues comes down to tubing wear and differences in head/draw pressure from the new salt water and the old salt water source. First, those quick lead heads are the cheaper cole parmer heads and even slight differences in tolerances in the rollers will result in differences in the tubing wear and flow between the two heads. Then comes head pressure. Different lengths of tubing from one head to the next to and from the source coupled with the height you are drawing from and the height the water is being expelled to will impact the flow rates. As such, I would expect there to be a difference in flow rates between the two heads.

Some of the higher end Easy Load heads have an adjustable occlusion that will allow you to make slight adjustments in the amount of pinch on each set of tubing. This can be used to adjust the flow rates from one head to the next. In your case, you would need to use a needle valve on one of the tubes to adjust the flow rate of the one that is producing more water than the other in order to restrict the flow rate slightly.

[Gorgok]

Restricting the flow on a positive displacement pump is just asking for trouble... It will still flow the same, eventually, through the restriction or fail. I use fail loosely here, as it could be the rollers leaking back to source due to high pressure or more catastrophically blowing the tube open.

Since these can't be calibrated by runtime (like cheaper pumps do it), they have to be calibrated by volume of the displacement. Which is just the tube. This would also be why the good tube costs more.

A tighter pinch will just allow the unit to pump against higher back pressure before leaking back, it shouldn't change the volume of the stroke.

[bulabr]

Since there are a lot of influence`s factors which will go affect the flow in the final of the hoses, I believe that it is better to set up all system, and test again, because it will be a long journey between the tank, and the saltwater container and the drain. Anyway, is there someone that knows about this company McMaster and its products?

[Gorgok]

The only thing that matters is the tube in the pump. You can be spraying the output into the air or down an airline tube and it will flow the same as long as your pump itself isn't leaking or stalling.

Positive displacement really is quite simple stuff. Its just like a syringe. Measuring 10ml of water and shooting it straight into a test tube is the same as shooting it down an airline into a test tube or through a valve and a hose into the same test tube... It doesn't change the fact you put 10ml of water into the thing. The tube in the pump is that syringe body and the rollers are the plunger.

As a side note, you cannot test the system for accuracy without priming it first. If the airline or the valve/hose assemblies (assuming they are air tight) are dry they will measure wrong (more accurately nothing) until the lines are full. But once they are full its irrelevant how big or small the system is. Non air tight systems would be equivalent to spraying in the air straight off the pump and drain down at whatever pace they decide to drain down at, but the volume will still be dictated by the pump alone.

[slief]

Originally Posted by Gorgok

Restricting the flow on a positive displacement pump is just asking for trouble... It will still flow the same, eventually, through the restriction or fail. I use fail loosely here, as it could be the rollers leaking back to source due to high pressure or more catastrophically blowing the tube open.

Since these can't be calibrated by runtime (like cheaper pumps do it), they have to be calibrated by volume of the displacement. Which is just the tube. This would also be why the good tube costs more.

A tighter pinch will just allow the unit to pump against higher back pressure before leaking back, it shouldn't change the volume of the stroke.

Using heads with adjustable occlusions is how Cole Parmer recommends fine tuning flow rates between stacked heads and I know from first hand experience that it will impact the flow rates from one head to another as head and draw pressure does in fact have a slight impact on flow rates. It doesn’t take much of a difference in head or draw pressure to have an impact on the flow rate however small it may be. In the case of using these pumps with stacked heads for automatic water changes which precise volume is critical, those kinds of adjustments are needed and critical to balancing flow between stacked heads.

From the Cole Parmer site discussing the balancing of flow in multichannel pumping. “To ensure accuracy, it is important to use high-tolerance precision pump tubing and to calibrate the pump. "High tolerance" means that the internal diameter and wall thickness of the tubing have been held within very narrow tolerance limits during manufacture. Minimal variations in the dimensions of the tubing translate directly into minimal variations in flow rate. Calibrating the pump; by adjusting motor speed, run time, or occlusion (the squeezing force applied to the tubing); will further reduce variation and improve repeatability. Always calibrate the pump under actual application conditions (fluid type, temperature, etc.).”

https://www.coleparmer.com/tech-arti...hannel-pumping

[slief]

Originally Posted by bulabr

Well... can I trust in McMaster products?

McMaster is a very good company. I’ve used them for all kinds of things.

[Gorgok]

Really the only thing occlusion should do is reduce/eliminate slip. But i would have assumed these things are setup to not have any already. Maybe its not set quite so tight to increase tube life and under high loads that is not enough.

But slip shouldn't exist in the test above, where there is no pressure to speak of. If it does then the setup is wrong.

[slief]

Originally Posted by Gorgok

Really the only thing occlusion should do is reduce/eliminate slip. But i would have assumed these things are setup to not have any already. Maybe its not set quite so tight to increase tube life and under high loads that is not enough.

But slip shouldn't exist in the test above, where there is no pressure to speak of. If it does then the setup is wrong.

In the OP’s case, he’s got kind of crappy heads and definitely the wrong heads for this application where precision in flow between the stacked heads is critical. I’ve played with those same heads he has on other Masterflex pumps and there is a fair amount of flex in the casing as the rollers spin with the tubing inside where the casing clamps together and if these are the ones I am thinking that hold together with a clip, no two heads will ever be the same due to the flex in the head casing and the clips as the tension or memory in the bend on those clips will change over the years. This will account for his flow variances from one head to the next. The Easy Load heads on the other hand are much sturdier and have tighter tolerances due to the lever style clamping mechanism so they would be much more accurate right out of the gate. As for the occlusions, their primary function is to prevent tubing from “walking” forward in the head but their secondary function would be to impact flow a bit as noted in the above link. That said, the more precise nature of the Easy Load heads vs the sloppy nature of OP’s quick load heads would likely solve his issues but I don’t think the Easy Load heads will work with his motor due to the mounting screw hole spacing which I am pretty certain differs from those heads he has now.

[on the spot]

Originally Posted by bulabr

Well... can I trust in McMaster products?

Maybe.


Slief posted the best lift from Cole Parmer regarding the tubing - use the most precise tube you can.

I still expect this only matters in the actual head itself.


Keep us posted how this turns out.

[porterfan]

Check out Youtube for a calibration video on the L/S pumps.