Sulaiman - 9-12-2017 at 04:46
Recently I bought six ex cow-milking-shed peristaltic pumps via eBay uk to circulate cooling water for my distillation rig
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(GBP24 so far for six pumps, three pwm controllers and replacement silicone tubing)
The units that I bought were c125 rpm @ 12Vdc,
which equates to 0.5/2/4.5 ml/sec depending upon bore size 1.6/3.2/4.8 mm i.d.,
I chose 3.2mm i.d.
I noticed in the data sheets that peristaltic pumps could be used to generate negative pressure, so today I tried,
a single pump, 125 rpm, 2ml/sec, pumps down much slower than my piston or rotary pumps, but soon reaches pressure levels around 38mm Hg (5 kPa, 0.05
ATM)
... more than adequate for most reduced pressure distillations and filtrations.
I hope to try a reduced pressure distillation early next year using one of these pumps,
I guess that by the time the pot gets up to temperature the vacuum will be adequate - if my rig is not too leaky 
Two pumps in series produce about 20mm Hg absolute pressure.
The amazingness is due to the low cost, easy maintenance, reliability,
the constant metered flow rate, pulling or pushing, liquids or gasses,
and the ability to choose chemically resistant tubing !
(I may upgrade one or two pumps from silicone)
So, if you see cheap peristaltic pumps - they may be of use to you ?
(but consider the low flow-rate for your application, and the requirement for a 12 Vdc supply)
P.S. if you do replace peristaltic pump tubing, it is the wall thickness and material that is important,
any i.d. within the pumps specified range is allowable, it determines flow-rate.
e.g. in my case 1.6mm wall, 1.6mm to 4.8mm i.d.
also, the cheap 10A pwm controllers via eBay control flow-rate/speed nicely down to <10%
10A (more like 8A) is overkill but I've successfully used these modules for other things so I use them by default,
even though a lower current module (e.g. I have tried the mini 5A module and it works fine with these pumps) could save me GBP1 each.
P.P.S. the pumps that I bought had internally clean, greased gearboxes and little wear of the motor carbon brushes,
the only problem that I have found is that the tubing needed replacing !
[Edited on 9-12-2017 by Sulaiman]
XeonTheMGPony - 9-12-2017 at 06:12
large inkjet printers have small pumps in them used for head cleaning, all so used in commercial laundry equipment and in pool and spa systems for
chem metering.
So a few places one can go asking for old units or no longer needed spares