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Correct type of vacuum oil


#1

I have a Vigor Model 082 Vacucast casting machine/vacuum investment
debubbling machine and the vacuum motor has a slight leak and is
losing oil.

We plan to fix the leak but I would like to know what kind of oil to
purchase to refill the reservoir on the vacuum motor.

Will any vacuum pump oil work?

Appreciate any help I can get on this!
Thanks!
John Dyer
www.johndyergems.com


#2

John- We just use standard pump oil for our home made vacuum pump.

Have fun and make lots of jewelry.
Jo Haemer
www.timothywgreen.com


#3
Will any vacuum pump oil work?

Yes.


#4

Hi John,

The various vacu-cast rigs have had different pumps over the years.
A quick google gives me nothing of use in figuring out which type of
pump you’re likely to have. (There are two likely suspects: older
machines had rotary pumps, while newer ones (20ish years) have vane
pumps.) This matters because the two different pump styles require
different oil. If you look around the back of the unit, and look at
the pump, the two types look different. If the pump looks like a
brick with a pulley sticking off the side, leading back to a
separate motor, it’s a rotary.

If it looks like a motor with a box stuck to the end of it, it’s
probably a vane pump. (Newer rotaries look like that too, but
they’re pricey enough that you’d notice. ) (If you think you’ve got
a vane pump, look at the nameplate. Unless it says Welch or Alcatel,
you’ve probably got a vane pump.) (Rotaries also chug and burble
sort of like a steam engine with a sore throat. Vanes just whirr.)

If you’ve got a vane pump, just call Rio or any of the normal
jewelry suppliers and get their normal vacuum pump oil.

I’ve got big rotary pumps, and I use Lesker TK-19. Welch Duo-Seal
oil will also work just fine.

If you’ve got a rotary, don’t use the jewelry suppliers standard
flushing oil either. That’s for vane pumps too.

Regards,
Brian


#5

Welch Duoseal oil or its equivalent will work well.

James Binnion
James Binnion Metal Arts


#6
This matters because the two different pump styles require
different oil. 

What are the differences, Brian? I’ve always thought that pump oil
is just a light straight weight gear oil. It would probably have made
sense to use lighter weight in vane pumps and silent compressor pumps
(similar if not identical to refrigeration pumps), but I never
considered it to be any big deal.

I’ve changed the oil in my old rotary pump about every year (OK,
maybe two, three? or if it ever starts looking a little milky) and
have always used the same silent compressor oil. I’ve used the old
pump to evacuate my car’s a/c several times and each time flushed and
refilled it with the same type of compressor oil. It’s been working
great for at least twenty five years (I bought it well used in '87)
and it still pulls 29 lbs. in about 40 seconds, but I don’t want to
shorten it’s life anymore than I already have. I guess clean oil even
if it’s not the right type is better than the right oil that’s dirty,
or none at all, but I’d rather use the right stuff.

Thanks!
Dave Phelps


#7

Hi David,

My understanding, from a very rough conversation years ago, was that
rotary oil had more lubricants in it, because the wipers on the
rotary pumps actually rub around against the inside of the pump
chamber, while vane pumps just spin really fast, so they don’t need
the lubricant quite so much. (Nothing touches, despite how fast it’s
going.) Keep in mind also that most of what I know about pumps, I
learned from physics grad students who cared rather more than we do
about ultimate vacuum and chamber purity. It may be that it’s just
fine to switch oils in a non-critical application like investing. I
got started with TK-19, and it’s not that much more expensive than
the cheapo stuff.

Regards,
Brian


#8

Basically there are 2 types of oil used for vacuum pumps, mineral
(or synthetic mineral) and silicone oil. As long as you use the same
sort for topping up the brand or viscosity will not matter too much.
You can drain the pump, put some flushing oil through it and then
refill with any rotary vacuum oil and that way there is no chance of
getting a mineral oil and silicone oil mixed Silicone oil tends to be
expensive so you probably dont have that.

Nick Royall


#9
I have a Vigor Model 082 Vacucast casting machine/vacuum
investment debubbling machine...what kind of oil to purchase to
refill the reservoir 

The vacuum pump that originally came in your machine is a vane pump
and vacuum pump oil from jewelry equipment suppliers is fine. You can
also get it from places that sell vacuum pump oil for AC and
refrigeration servicing vacuum pumps like Johnstone and Grainger.

Brian,

Please contact me offline about your distinction between "rotary"
and “vane” vacuum pumps.

John
The Jewelry Equipment Dr.


#10

Hi John,

Most of this comes from about 15 years back, when I was dating a
physics grad student. I helped her rebuild a number of Welch pumps,
and ended up with about half a dozen of the ones nobody wanted.

So, what I meant by rotaries are the classic Welch duo-seals, like
the 1405, 1402, 1397, 8821, etc. Big huge disk set eccentrically
within a cylindrical chamber. Two opposed wiper blades, spring
loaded so that they ‘wipe’ along the walls of the chamber, forming a
self adjusting seal against the wall of the pump chamber.

What I meant by vane pumps are more like tubo pumps, now that I
think of it. I’ve never gutted one of these, so this is going on
what I was told. As I understood it, these pumps work by way of a
spinning rotor of lots of little blades that essentially slings the
gas out by centripetal force as the atoms impact the whirling
blades. Never gave it a whole lot of thought, but now that I do, I’m
a little puzzled about what the oil does in these things. Thinking
about it now, I’d expect it to get in the way. Anyway, given how
they work, they can move a lot more gas, a lot faster than a
duo-seal style pump, but have trouble with ultimate vacuum. More of
a roughing pump. (even more of a rougher than the Welches.) From
discussions we had at the time, the vane style pumps needed lighter
oil with less lubricant in it than the Welches did. Unfortunately,
all I’ve got around here are Welches, so I don’t have an example of
a vane pump to give you a model number. Let me check in the
vacu-cast machine out at school, and I’ll see what kind of pump it
has, and maybe that’ll help give a handle on what I’m talking about.
(It’ll take about 2 weeks, we’re on break.)

I’m not totally making this up, really.

Regards,
Brian