Sulaiman
International Hazard
Posts: 3698
Registered: 8-2-2015
Location: 3rd rock from the sun
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warning ... eBay 80 kpa vacuum pump unreliable
Because I sort of endorsed a cheap vacuum pump in another thread ( DC12V 80Kpa DC Micro Piston Vacuum Pump )
I want to warn that it is not reliable.
The metal pin in molded plastic bearing, which is a part of the piston,
melts the plastic and destroys beyond repair the bearing.
I bought one, liked it, played with it and ordered a second similar pump
(I was considering two pumps in parallel operating alternately to reduce the duty cycle and provide redundancy)
In identical conditions to the first, the second one failed in about 4 minutes 
I'm going for a refund, not important, I just want to retract my endorsement.
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Zombie
Forum Hillbilly
Posts: 1700
Registered: 13-1-2015
Location: Florida PanHandle
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Mood: I just don't know...
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These?
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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Sulaiman
International Hazard
Posts: 3698
Registered: 8-2-2015
Location: 3rd rock from the sun
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Exactly the one.
It should be able to perform nicely as a filtration vacuum pump
and produce low enough pressure to usefully lower boiling points for distillations etc.
The bearing of the first one I bought got quite warm in use
so I disassembled the whole pump,
removed the white grease from the bearing, piston, valves etc.
and replaced it with the thin silicone grease that I bought for Quickfit joints.
It runs quite cool now.
The second one i ran as received and it died in a few minutes.
I will drill out the bearing in the first one and insert a bearing sleeve if I find one cheap.
I bought this type of pump as a simple partial vacuum source
relative to a rotary vane pump, that I could not worry about contaminating.
I guess I'll have to bite the bullet and buy a rotary vane pump.... drat!
(I wanted a rotary vane vacuum pump for some electronics related projects
but couldn't justify it to myself, now I can sort of justify the cost to myself)
I try to spend as little as practical on hobby stuff hence 100's of cheap Chinese products via eBay
(Electronics, astronomy and now chemistry)
On average I am pleased with the overall savings and value for money
I do not recall any individual components being faulty
but anything assembled is best tested (in case of complete failure .. refund)
then disassembled and reassembled because quality control for cheap consumer products seems minimal.
UPDATE: money refunded already and no need to return the faulty pump.
This is the other reason I like cheap Chinese eBay goods,
the sellers have always been VERY quick to sort out problems... well done to the Chinese !
P.S. I will try a repair of the now free pump.
I have found tubing with intermal diameter 2mm to match the pin,
any advice, brass or stainless steel, Chinese eBay quality of course !
[Edited on 30-5-2015 by Sulaiman]
[Edited on 30-5-2015 by Sulaiman]
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Zombie
Forum Hillbilly
Posts: 1700
Registered: 13-1-2015
Location: Florida PanHandle
Member Is Offline
Mood: I just don't know...
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Brass. You need your bearing to wear instead of the shaft.
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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