Australia's Science Forum

Hi all,

We need to purchase a new vacuum pump, what do you all recommend?
My H.T. wants a good one, she looked in the Labtek catalogue and saw a Diaphragm vacuum pump for $865.
They also have a Rocker 300 vacuum pump for $521.
Does anyone know what the difference is between the two, she has no idea and neither do I!.........

Thanks in advance,
Helen.

Hi Helen
I'm sure someone here will be able to explain the difference - I can't. But a couple of years ago, I was looking to replace our vacuum pump and was recommended that I buy an oil-free one. I never did actually buy it as I changed schools shortly after.

Hi Merilyn,

Yes, the little bit of research I've done seems to suggest most of them are oil free now.
Which is where I was hoping to head!
I just don't want to waste money on a fancier one if the cheaper ones are sufficient for our needs.

Only thing I can see is that diaphragm pumps are more chemical resistant than the rocker which I think is the piston type .

I guess it depends what you will use it on and the likelihood of corrosive vapours etc getting sucked into it . If it was just for bell jars and perhaps sucking some chalk through a glass crucible type setup I'm sure the cheaper one would last a lifetime.....the rate we use them .

However , I'm just a sceptical bastard though so I can't help but think that a piston in a bore with no lubrication ( oil free) is not going to last

Ha Ha bigmack,

I hear you!!
The one we had worked fine, it was just a basic little one......but it seems that it grew legs.....

Hi all!

Just had the joys of discovering the oil of our vac pump hasn't been changed in ages. Flushed out the old stuff and replaced it with what we had in the storeroom. The old container didn't have any true labels on it. I was wondering if anyone knows what type of light machine oil I can buy and where?

Adding to my previous question.

The vacuum pump has possibly overheated and doesn't turn on anymore. The fresh oil I had just put in has drained out opaque instead of clear. Any thoughts on what could have caused this? Should I add it to the list of repair jobs (external) or try to buy a new one?

We have the pumps sold by Westlab https://www.westlab.com.au/equipment/eq ... head-gauge they do the job for what students need and easy to maintain

MissKat wrote: ↑18 Mar 2021, 13:41 Adding to my previous question.

The vacuum pump has possibly overheated and doesn't turn on anymore. The fresh oil I had just put in has drained out opaque instead of clear. Any thoughts on what could have caused this? Should I add it to the list of repair jobs (external) or try to buy a new one?

Is it possible that you have sucked some moisture into it ?. Let it dry out for a bit then try to turn it on again. Sometimes we run ours without a vacuum trap between the flask and the pump....often teachers suck liquids into them by accident.

Anna Z wrote: ↑20 Mar 2021, 08:50

MissKat wrote: ↑18 Mar 2021, 13:41 Adding to my previous question.

The vacuum pump has possibly overheated and doesn't turn on anymore. The fresh oil I had just put in has drained out opaque instead of clear. Any thoughts on what could have caused this? Should I add it to the list of repair jobs (external) or try to buy a new one?

Is it possible that you have sucked some moisture into it ?. Let it dry out for a bit then try to turn it on again. Sometimes we run ours without a vacuum trap between the flask and the pump....often teachers suck liquids into them by accident.

Thank you so much. One of the Science Extension students was using it so it quite possibly be the cause. I'm going to let it dry out over the school holidays.

Where can I buy the oil suitable for the vacuum pump?

Years ago I bought a Welch pump, & it's a great little piece of equipment. It's both a vacuum pump & compressor, so great for inflating lungs/balloons, & also sucking the air out of flasks of leaf discs etc.
They're harder to find now, but I'd highly recommend getting one. Fisher Scientific & Thomas Scientific have them, & maybe also eBay.

I asked our supplier which oil to use a few years ago and he sent me this. (The vacuum pump looks the same as MissKat's).