Vacuum Pump/Compressor Question ID

[RMO]

I was visiting the surplus sale at the university where I work and this vacuum pump/compressor followed me home. The maintenance man for the engineering department where this was used indicated that he thought is could be converted to a compressor. It runs quiet and I thought it might work to run an engine on air if I every get to that point. My question is this, does anyone out there recognize this unit? It is a B&G Oil-Less Air Compressor on a small tank. When plugged in it pulls a nice vacuum in the tank. Just wondering if I could reverse something so I can also use it as an air compressor for low volume applications. Hopefully the photos will show up.

Mike O

 

[terrywerm]

Mike,

Sad to say your photos did not show up. As for switching anything around, it is really hard to tell without the pics. Don't feel bad about them not appearing, as it seems to be a common problem with the new forum software.

Just as an experiment, a small pic should appear here:

It appears that you have to have your pics on a published website already, not passworded. Add the link to the pic(s) and it (they) should appear.

 

[RMO]

Strange as I used the new software to upload them. Your test photo did show up. I will try again.

 

[RMO]

Well it appears that attaching the photos will not work and I don't have them uploaded to any website so I am not sure how to put on a link. Interestingly enough in my original post the photos appeared in the preview.

MikeO

 

[RMO]

I guess they got they got the photos working....not sure about the rest of the site.

 

[kf2qd]

Looks like that is a compressor. All the oiless units like that that I have seen would rely on some back pressure to get the rings to seal as they are generally composition material rather than cast iron for the rings. Have worked on a couple. 100PSI, though they can be a bit slow to start building pressure, once they get 20PSI they do seem to build at a faster rate.
Might want to pull those gray plastic caps off and clean the filters. If you were to build some manifolds and go to a common replaceable filter like an automotive filter the compressor would not complain.

 

[RMO]

Thanks, I thought it looked like a compressor too. The interesting this is that as it runs, air comes out of the gray caps, not in. The air is pulled from the tank into the compressor and then out of the gray caps. I was wondering how to reverse the process somehow.

Mike O

 

[terrywerm]

Mike,

Compressors and vacuum pumps are pretty much one and the same. Both use reed valves in the head to control the flow of air.

In a vacuum pump, the intake valve is located at the pipe to the reservoir, and the air exits through a muffler.

In a compressor, the intake valve is located at the filter, and the air exits through the pipe to the reservoir.

So, in some cases, you can remove the heads and swap the valves around. In other cases you can remove the filters, then remove the fittings that contain the valves, and switch them around. This is the most likely case with your unit, as near as I can tell.

I am glad that your photos finally appeared. When I was in high school, I worked part time for a neighboring farmer, and he had an air compressor that looked exactly like your vacuum pump, same color and everything!

One thing that might be a big problem is the tank. In most cases vacuum tanks would be engineered a bit differently than pressure tanks. It would be a good idea to examine the tank carefully for any indication of how much pressure the tank may be certified for. Whatever you do, please don't use the existing tank for air pressure unless it is certified for such use. None of us want to see a future post from you or a family member indicating that you were either killed or maimed when the tank blew up!

You will also need to add a pressure relief valve, of a proper setting for the pressure tank you use (this is a MUST DO!). You will probably want to add a pressure control switch also, so that once the pressure builds to an adequate set point, the compressor will shut off.

If you have further questions, feel free to post 'em here!

 

[walnotr]

Several years back we had a high pressure tank shear off it's bottom plate. It turned into an instant rocket going through a concrete floor above it, through that room and out the ceiling and traveled several hundred feet up before returning to earth. Fortunately no one was in the path but the amount of damage to windows and the building was pretty amazing. Not to mention some ringing ears for awhile. I have always had great respect for any kind of tank since then. There is an amazing amount of energy stored in them and it doesn't take a lot of pressure to cause damage. Pressure relief valves are a must, and should be tested frequently. Drain the moisture out of the tank often as well.

 

[RMO]

I agree with the advice and had planned to add the relief valve and pressure switch, in fact I have a brand new one of each, I just need to figure out the capacity of the tank I have other compressors for the shop use, I was just interested in a low pressure one for this and that. Thanks for the advice. Now to figure out what to change.

Mike O

 

[terrywerm]

Mike,

Good to hear that you were already a step ahead of us on the safety valve and pressure switch. Please don't forget to make sure the tank is designed for pressure before using it for such. (Ok, enough of that, afterall I don't need to sound like your mom!)

Let us know how you make out with the heads and valves on the compressor. Those were fairly common units years back, and they were better units than most folks expected.

 

[ianh]

Just a quicky from a guy that used to be in the heavy compressor industry. Your vacuum pump was made normally for dentists, it's the bloody thing that sucks at your tongue!. A vacuum pump and a compressor are the same thing engineering wise, you will have to turn the pipework around add a safety valve of suitable capacity and a drain and away you go. These little compressors should give you about 60 -90 psi.Please remember to check your safety and drain cocks regularly. Both Pressure and Vacuum vessels are extremely dangerous so be careful out there.

 

[RMO]

Thanks again. I was able to remove the gray caps a d plug on the heads and found reed valves underneath. These screw out and can be swapped. This should convert it to a compressor. Looks like it was made to go either way. In fact the tag on it calls it a compressor. I will get some pics of the valves shortly.

 

[RMO]

Got it figured out. Underneath the gray caps and the plug there are round reed valves that screw out. I just swapped the reed valves and turned the check valve in the output line around and it works great. Of course I have not let it build any significant pressure other than my finger over the tank outlet for a bit. I have to get the pressure switch and relief valve setup first. Thanks guys

 

[Tin Falcon]

good to hear you got it sorted out.
Tin

 

[tornitore45]

A vacuum tank must resist a crushing pressure of 15 PSI at most. If it leakes no big deal, if it weakens internally it will crush witout much destruction. Pressure tanks may need to take 150 PSI or more, failures can be a big deal.
Perhaps you vaccum pump was born as a pump and converted, but if it was engineered as a vacuum beware of the tank.