Author Topic: compressor question (Read 3098 times)

willib · « **on:** June 15, 2006, 10:27:05 PM »

this is the compressor i'm going to use for my vacuum bagging operation.

since i dont want to eff this one up , i need some advice

would where the arrow is pointing be a good place to cut the line?

will the compressor last for any lenght of time without the oil enriched R22?

Phil Timmons · « **Reply #1 on:** June 15, 2006, 05:28:35 PM »

Sorry but can you start a little further back with the concept?

By "vacuum bagging" I am thinking you mean like sucking air out of a plastic bag that has something to be stored placed inside of it? So you would be using an old freon compressor on the suction side (the larger copper line) to create this?

I have not seen anyone try this, so this is all just supposing . . .

Since the oil and freon parts of a refrig pump mix together, I think the moisture from the air will be sucked directly into the system oil. Not a good long term plan. Second, the oil will be discharged out the pressure side of the compressor. While that is normal, when that happens it usually travels through the refrig system and returns by the suction side. If your system has been cut apart, what will be the return path for the oil?

My guess is that you may have a more functional rig by using a normal air compressor that has an upper (air) and lower crankcase section (oil reserve). Just use the intake side for the vacuum. Or maybe even a little oil-less compressor? I use the little Thomas oil-less compressors for projects like this.

willib · « **Reply #2 on:** June 15, 2006, 05:54:48 PM »

yes vacuume bagging is sucking the air out of a bag to compress glass fibers evenly when making a laminated epoxy-glass structure ,ie mold.

that was my question , how long will the compressor last without oil?

thanks for the tip on the thomas oil-less compressors

this one was free , and only has to suck the air out for a few seconds/mins at at time , till the vacuume depletes then i will have start it up again

Phil Timmons · « **Reply #3 on:** June 15, 2006, 06:07:21 PM »

Ahhh!

OK. Gotta ya!

You are just talking about short use, very infrequent use.

Yeah, I would think you could do this. I guess I might do something with the discharge line (the smaller high pressure side) and have it routed around so it can blow back partly into the cut suction line. That way the oil recirculates back into the compressor.

But for being lazy, have you considered using a vacuum port off a car engine? Like what runs the brake booster and the heat/air controls? That seems like a good Red-Green sort of fix for a vacuum that I might just try. I think the Army term was "Field Expedient" -- rather than call it hacking.

Suppose I should not make too much fun about misusing the tools given us. I bend PVC conduit by stuffing it up the tail pipe of my work truck . . . .

Volvo farmer · « **Reply #4 on:** June 15, 2006, 06:57:07 PM »

When I saw that compressor, a little warning flag went off in my head. Have you actually seen this thing run and cool? What you have there is a rotary vaned compressor. They tried putting these things in domestic refrigerators about twenty years ago and just about every single one of them failed in five to seven years. Nowadays, every single manufacturer has gone back to the old fashioned reciprocating compressors.

You say this thing has R-22 in it so I'm assuming air conditioner, It's possible that these things hold up better and are still used in that application, I don't see many A/C units so I don't know.

If it was a reciprocating compressor, I'd say it would hold up for quite a while in your intended application, especially if you only run it ten or twenty minutes at a time. I don't know much about those rotary units but I do think it is important to keep the seals well oiled, where as a reciprocationg compressor might be a little more forgiving in this regard.

KEG · « **Reply #5 on:** June 15, 2006, 06:59:02 PM »

Hi Willib

Has the freon been pumped out or been lost ? and how much vacume are you after and how long? For a real good steady vacume get ahold of some one in hvac-r and use a real vacume pump that will get the vacume steady and deap. I would also think a shop Vac with good motor will pull a better vac then that compressor, just a thought!

Kevin

willib · « **Reply #6 on:** June 15, 2006, 07:43:39 PM »

The freon is still in there , it still works , gets cold and everything ,

the last one i tried actually got down to 27 inches Hg vacuum , it was the bubble type or roundish looking compressor, but i threw it out because it went kaput.

it had a faulty thermal switch on it , anyways its gone.

volvo farmer , this one is sort of , relatively new.

it sounds like its reciprocating

Keg , How long?

i figure that at 100F degrees the epoxy should be cured in about 4 hours , it all depends on the seal of the bag, and since i can turn it on and off , when needed ..

it would be nice to make it automatically come on ad go off , but since this is only going to be needed twice , one for each side of the blade , i'm just going to have to keep an eye on it.

willib · « **Reply #7 on:** June 15, 2006, 08:02:01 PM »

its a dehumidifier , it runs on 115V @ 6.5A

i got it for free , the fan came off and they threw it out, i put the fan back on and it works great.

it does sound like a reciprocating one

what a waste of energy the beast is , i would never use it for its intended purpose..

RickieBlue · « **Reply #8 on:** June 15, 2006, 08:13:56 PM »

That compressor will work just fine. I used one of these compressors to evacuate A/C systems for years. It will pull a decent vacuum and should be good for your application. The oil problem is a real problem though and to get by that, I used to dump oil into the suction port before I used it....2 ounces or so..never had a noisy compressor using it like this. As long as your unit is running, why not just keep it intact and go to your local white goods recycler, maybe a municipal operation and see if they will allow you to cut a compressor out of one of the white boxes they have picked up? And the deal about using engine vacuum..that will give you about 18 inches at the most, and the compressor about 28 inches. You would be suprised on the work 18 inches of vacuum will do for you though. Just my 2 cents worth. ....Rick

willib · « **Reply #9 on:** June 15, 2006, 08:41:54 PM »

thats good news , what kind of oil did you use?

the way i look at it , i'm doing someone a favor by putting this power guzzling beast out of it former misery, 6.5 Amps !

hmmm i wonder what the motor looks like on the inside?

Volvo farmer · « **Reply #10 on:** June 15, 2006, 10:19:31 PM »

Well, you would probably use it, if you had a warehouse with a clean room and hundreds of thousands of dollars of equipment that would be damaged by humidity :-)

I still say you got a rotary compressor there. It would probably work just fine though. I've thrown away dozens of good compressors since the EPA made it basically a crime to re-use refrigerant and R12 is twenty times more expensive than it was fifteen years ago.

Maybe someone who needs a dehumidifier would buy the thing off you, I'll give you as many free refrigerator compressors as you can pick up or pay freight for. I realize this thing you got was free but if it still works, it seems a shame to destroy it for it's compressor. People are PAYING me to dispose of their old refrigerators because I'm EPA certified, the landfill will not take the things anymore with the compressors intact. Maybe there's someone in your locale throwing away as many compressors as I do.

Older stuff used regular old mineral oil, R22 would fall into this category, R134A and other newer blends often require PAG synthetic oil.

willib · « **Reply #11 on:** June 15, 2006, 10:31:19 PM »

you mean to tell me that you cant take the refrigerant out of something and use it in something else?

thats a little stupid ,if the epa was worried about ozone depletion you would think that they would welcome reusing it.?

ghurd · « **Reply #12 on:** June 16, 2006, 08:05:52 AM »

I recently spent a lot of time looking into about the same thing, but for compression.

What I was told or read, about 'fridge compressors... (tablespoon of salt)

Let it run open for a half hour, to finish spewing excess (normaly up in the lines) oil out.

A verticle 4' piece of 4" pipe, maybe with some baffles, to catch and return oil, is a good idea.

About 1/2 cfm at most pressures, could reach over 350PSI.

"It'll last for years".

I know how you feel. :-( There isn't much info floating around, and much of it is contradictory.

G-

willib · « **Reply #13 on:** June 16, 2006, 11:42:38 AM »

does this help

http://www.otherpower.com/images/scimages/2965/IM002126.JPG

WXYZCIENCE · « **Reply #14 on:** June 16, 2006, 01:12:22 PM »

Willib, I built one years ago using an old automotive air-conditioning pump. They are rugged and I just add a couple of drops of oil into the unit before I use it. It is belt driven and I also use the magnetic clutch in idle mode. Lots of vacuum. Joe.

Ungrounded Lightning Rod · « **Reply #15 on:** June 16, 2006, 03:21:43 PM »

I'd make a jar with oil and a couple pipes, one long one short, so the air being pumped out of the target bubbles through the oil on its way to the compressor. This should pick up enough oil droplets to keep the compressor happy. (Make a small controlled leak in the vacuum line upstream of the oil bubbler if you want to keep it running to hold a vacuum for a long time.)

You can also use a similar jar for an oil trap on the output side. (This time you use two short pipes.) Then pass the exhaust from that through a bundle of cloth to catch the last droplets. (See a commercial vacuum pump for how that's done. That cloth-holding thing isn't JUST a muffler. B-) )

The oil bath will also help catch dust before it gets into your pump.

willib · « **Reply #16 on:** June 16, 2006, 05:34:20 PM »

i'm going to need another valve , the suction part was actually the other line , ( the one not pointed to )

it does get down to 25 or so inches of vacuum , it does'nt hold a vacuum like the first one. when i shut it off it leaks past the rotors .

it is a rotary compressor btw..

so i need another valve to keep air from leaking into my vacuum

there was no oil in the line at all

Volvo farmer · « **Reply #17 on:** June 17, 2006, 05:54:40 AM »

Yeah, that's one advantage of the reciprocating units, they use a reed valve.

A schrader valve would work, but you'd have to figure out how to hook it up in reverse, since the sweat-on part is usually designed to go towards the pressure.

RP · « **Reply #18 on:** June 17, 2006, 05:44:29 PM »

Go to the autoparts store and tell them you need a power brake booster vacuum check valve. It'll have two hose barbs on it and you can connect it in-line with your pump.

SamoaPower · « **Reply #19 on:** June 17, 2006, 06:24:59 PM »

A bit of over-kill willib.

You only need 7-18" of vacuum for vacuum bagging and the higher end is for high density structural (blue) foam. Too much vacuum will crush your foam.

Please use an adjustable vacuum switch to cycle the pump as needed unless you plan to baby sit the job for 12 hours.

You might consider using a food saver (vacuum food storage system) as a vacuum source. I'm sure you can pick these up on eBay at a good price.

willib · « **Reply #20 on:** June 17, 2006, 07:52:18 PM »

Its been holding steady at 22" Hg vacuum for 36 min. it hasnt budged during this latest test

i'm about to mix the epoxy in a little bit .

it "should" hold 7 to 18" vacuum no problem , havnt tested it with the bag though, but there isnt much point in bagging it without epoxy just to rip the bag off and apply epoxy.

i have three layers of glass on there , i hope its enough.

i wish i had an adjustable vacuum switch , but i think in the oven (at 100F degrees ) it shouldnt take long to cure, maybe several hours

SamoaPower · « **Reply #21 on:** June 17, 2006, 10:03:31 PM »

I hope I didn't mislead you. It's not just anywhere between 7-18", that's the range for various types of foam densities. If you are using common, white, low density foam, I suggest you keep it at 8-10" if you don't want much crushing.

Good luck.

SamoaPower · « **Reply #22 on:** June 17, 2006, 10:19:59 PM »

Are you using a breathing layer and absorber mat?

Make sure and work the wrinkles out of the bag.

willib · « **Reply #23 on:** June 17, 2006, 10:31:55 PM »

i'll keep an eye on the crushing

the breathing layer will be several layers of fiberglass screening ( like for windows)

i could use some layers of fiberglass to make an absorber layer i suppose.

i've got the epoxy resin pump primed and ready .the hardner is next.

willib · « **Reply #24 on:** June 18, 2006, 02:45:55 PM »

well its curing

for better or worse

i guess i need to practice my bagging techniques , the question of how much vacuum to use is moot .

as it only holds 5" .

willib · « **Reply #25 on:** June 18, 2006, 06:39:01 PM »

this is it , the first half of the blade mold .

i chose the easier side (convex) the other side may or may not be the same difficulty.

it was so hot today that the epoxy was starting to thicken just as i was finishing .

i used west systems epoxy with the pumps .

the dark matte looking stuff is not carbon fiber it is fiberglass window screen , and i used it to allow for air passage .

i will separate the mold in a little bit , more pix to come

willib · « **Reply #26 on:** June 18, 2006, 11:13:24 PM »

all in all i think it came out pretty well.

on the left is the mold on the right is the blade

its going to need some touch ups and sanding when its fully cured , but i'm happy with the way it turned out..

willib · « **Reply #27 on:** June 19, 2006, 11:37:14 PM »

I got the other half done tonight its curing atm..

havnt taken any pix yet

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Author Topic: compressor question (Read 3098 times)