Hello all,
I built myself a simple setup (see the pic) to read waste water quality parameters from two different containers (in the pic i used only one). I'm using 2 peristaltic pumps( pumps ) driven with L293D motor driver.
Each pump pumps liquid from one container up wait for the sensor reading and then reverse and return the liquid back (around one minute of work and one minute of rest while the second pump is running).
I let it to run during the night after it worked well for 6 hours,in the morning when I came back, the pumps still worked but started to choke. (I assumed those pumps where not going to last for to long but already after one day? )
I will be happy for any suggestions on changing my setup (different type of pumps/motor for the pumps?) for them to be able to work reliably for months.
I pushed their limit by purpose now, I can probably let the pump rest a little bit more between the pumps cycles but my needs are to take a sample as often as possible during 4 hours cycles and I have 4- 6 cycles a day. (and no, unfortunately I cant use the sensor directly in the container)
Eitam:
Hello all,
I built myself a simple setup (see the pic) to read waste water quality parameters from two different containers (in the pic i used only one). I'm using 2 peristaltic pumps( pumps ) driven with L293D motor driver.
Each pump pumps liquid from one container up wait for the sensor reading and then reverse and return the liquid back (around one minute of work and one minute of rest while the second pump is running).
I let it to run during the night after it worked well for 6 hours,in the morning when I came back, the pumps still worked but started to choke. (I assumed those pumps where not going to last for to long but already after one day? )
I will be happy for any suggestions on changing my setup (different type of pumps/motor for the pumps?) for them to be able to work reliably for months.
I pushed their limit by purpose now, I can probably let the pump rest a little bit more between the pumps cycles but my needs are to take a sample as often as possible during 4 hours cycles and I have 4- 6 cycles a day. (and no, unfortunately I cant use the sensor directly in the container)
Thanks for the help
You mention waste water, but what is the waste? Particles, solvent, animal, vegetable? Are the pumps valving plugging up?
Why do you assume the short life of the pumps? There are NO specifications in the link you gave. What is the diaphragm made of? Time to do some forensic destruction.
Paul,
The man said 'peristaltic' pumps. Like in dialysis machines, printers, dosing pumps etc etc. Sadly, they are not typically intended for use as fast or high volume pumps.
OP,
I can only think that a centrifugal pump / impeller pump with a clearance between impellers and housing would be the way to go. These are the usual pumps for bilge and general purpose and I have seen these with maximum particulate sizes up to 3mm or more. But now I am assuming things about your application and answering my own assumptions which may not be helpful. So if you can fill me in; how much water do you need to move? How far? How high? Particulate size? Nature of contaminates? (acidic/alkaline?) Impeller pumps can be a bit violent, is that an issue? Impeller pumps are also not self priming, is that an issue?
PedantEngineer:
Paul,
The man said 'peristaltic' pumps. Like in dialysis machines, printers, dosing pumps etc etc. Sadly, they are not typically intended for use as fast or high volume pumps.
OP,
I can only think that a centrifugal pump / impeller pump with a clearance between impellers and housing would be the way to go. These are the usual pumps for bilge and general purpose and I have seen these with maximum particulate sizes up to 3mm or more. But now I am assuming things about your application and answering my own assumptions which may not be helpful. So if you can fill me in; how much water do you need to move? How far? How high? Particulate size? Nature of contaminates? (acidic/alkaline?) Impeller pumps can be a bit violent, is that an issue? Impeller pumps are also not self priming, is that an issue?
PE
Thanks PE,
I indeed used peristaltic pumps. You can see a picture of the setup as an attachment in the first post.
I only need around 5 ml of sample at a time (to fill part of the syringe doesn't have to be so accurate +-3 ml) the difference between the tank and the syringe could be 0.5-1 m max. the water are sewage water (toilet water) in liquid form (after a sinking tank and grinding). While they where working the peristaltic pumps did a great job, just wanted them to last for a lot longer. I'm not sure if the Impeller pumps can work with small dosage as I need.
the 'pump' of a peristalic pump is not the motor or impeller it is the tubing.
if you are running too fast and heating the tubing, it will not draw more fluid.
if your sediment gets imbedded in the tubing, then you need to filter.
I would recomend you check the documentation on the tubing to make sure it is not affected by your liquids and that it is desinted for use in a peristalic pump.
as for life expectancy, that is a trade-off of contaminants and longevigy
and with speed and heat vs. longevity.
if your tubing if fouling with biological growths, then cleaning is required at a frequency faster than the point of fouling.
Those peristaltic pumps look very familiar - I have the same. No idea on current they take as my multimeter can do only 250 mA. They draw more than that.
You can easily take off the head, and open it up to see the tube and the three rollers. Start there, see if anything is getting stuck there or so. Sediment I expect to largely be pushed through, unless it's sharp and becomes embedded in the hose wall. Bio fouling normally doesn't happen in a mere 6 hours.
Impeller pumps probably won't work for you. There are a few major differences.
They have no fixed flow rate, it depends very much on how high the liquid has to be pumped.
Their flow is usually much more (in the tune of 3-10 litres per minute vs. 10-100 ml/min), even for tiny 5V aquarium pumps.
When you switch off the pump, the liquid will immediately start to flow back through the pump (I'm actually making use of that for a flood/drain hydroponic system: an overflow to limit the level, and the pump hose doubles as drain).
Man this actually is a difficult problem. To pump just 5ml, a tiny 5ml! But you still have a 0.5m to 1m head to overcome and you need to do this several times an hour (as I recall). Hmmmm. Some random lateral thoughts:
If the water were flowing, being pumped around a circuit and at the top you had a small 'take off' point and maybe a solenoid valve or motorised ball valve so you could drop a sample out of the flow. This way you could use an impeller pump which would last forever and the higher flow rate would not be an issue but maybe an advantage.
Could you take this the other way around: move the sampling point into the tank? Move the whole analysis thing down to tank level so you don't need a pump at all.
Use a container to bring the sample up rather than a pump? Maybe lower and raise a sampling container with some mechanical arrangement of miniature winch type thing or a bucket elevator actually might be the thing to do.
Apart from the risk of splashing I'm thinking the bucket elevator is a pretty damn fine option.
Otherwise all I can say is that I think you picked the right pump technology for the sample sizes at least so if you have to stick with a peristaltic pump you might have to invest time and research the tube technologies.
I didn't ask before; when the pumps died, what went wrong with them? Which bit failed? Tube or motor or gear box?
Actually it's not as bad as you think it is. I've been playing a bit with these pumps, and see no issues doing 5 ml a time even with long lines.
My slowest pump is doing about 15 ml/min so that'd mean some 20 seconds of running for 5 ml, which is very reasonable. This is done by making the hose inside the pump head thinner so every turn of the rollers pushes out only a fraction of a ml.
The hoses it connects to are thin, <2 mm internal diameter. That's thin enough for watery solutions to not drip out. So your first dose is inaccurate, but as soon as the lines are full they stay full, so every new run of the motor pushes out the expected volume regardless of line volume and (within limits) the height difference the pump has to overcome.
)
