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26th Nov 2017, 02:25 PM #1
Drilling and tapping into a sealed vessel
Hi all...it's been a long time since my last visit....
I have a small project on the bench and that is converting a noisy compressor to use a degassed (professionally done), fridge compressor. I watched a gazillion videos on youtube and one particularly caught my attention 'cos the guy had actually drilled and tapped the casing to install a clear plastic "window" so that he could see the oil level inside.
He said he used a technique that allowed him to drill and tap without the metal shavings falling inside the vessel. I contacted him, but he ain't gonna say how he did it. Fat lot of good that is...So I was wondering is some good soul and citizen in here had any idea on how to do that??
I seriously don't want to cut the thing open and then re-weld it shut, even though I don't think that the vessel is under any pressure when running as the inlet and outlet pipes go and come from the piston/valve housing....
Anyway, thanks to all in advance
bg
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26th Nov 2017, 02:39 PM #2Most Valued Member
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You could try packing the tap with a thick grease to hold the swarf and position the job so that you are tapping from underneath, but still no guarantees that some wont drop off.
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26th Nov 2017, 03:33 PM #3Member: Blue and white apron brigade
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If you are going to install a window what's stopping you from washing the swarf out though the window using say kero??
If the window hole is too small can you pressurise the casing (via the oil supply or drain holes) to say 20-30 psi.
Then when you drill it the swarf will blow out.
When tapping the holes, connect a compressor and the block up all the holes except the one being tapped.
Add a magnet to the oil drain plug just in case any swarf got left inside.
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26th Nov 2017, 03:41 PM #4
BobL, yeah, got to thinking the same...One needs to change the oil anyway as the original is suitable for Freon/refrigerant gas only. The guy placed the same see-thru plastic plug "window" that you find on any oiled compressor.. So from memory the hole is about 1/2" in diam. big enough to flush everything out....good show..thanks...
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26th Nov 2017, 04:09 PM #5Member: Blue and white apron brigade
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The main issue you will have with wash out is any burr that is created inside the hole, but a round file should be able to remove that.
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26th Nov 2017, 04:55 PM #6Pink 10EE owner
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Will it work?
Fridge gasses are non rusting. As soon as you put atmosphere air into it, will it will get water and rust up?Gold, the colour of choice for the discerning person.
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26th Nov 2017, 05:28 PM #7
What about drilling it overhead . As you said 1/2" is not a big hole.
The chips and swarf have to obey gravity. Same with the tapping. You may not get 100% but the above suggestions are the fallback.
A bit harder to do certainly,but still doable.
Grahame
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26th Nov 2017, 11:20 PM #8Senior Member
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I would: drill, deburr with a Noga back-side deburring tool, tap with a spiral flute tap, deburr again, wash out with kero/turps/white spirit, and try and do the whole shebang with the new hole facing downwards to get a good gravity assist.
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27th Nov 2017, 01:02 AM #9Most Valued Member
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A standard way to tap a hole without creating swarf is to use a roll/firm tap. I have some in smaller sizes but I'd think they wouldn't exactly give away a 1/2" tap and it would be a big investment for one job.
I must admit I don't follow what the actual problem is here. As I understand it, you don't want any metal filings in the tank? Given the amount of crap I've seen coming out of air receivers I can't see how a bit of swarf off a drill will make much difference. With just a bit of care you won't get much in there anyway and I'd personally be more concerned about drilling random holes in a pressure vessel if it were me.
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27th Nov 2017, 01:37 AM #10Golden Member
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Do you have a link to the YouTube video in question?
You'll probably get a lot of oil mist coming through the line from the fridge compressor, not a big deal if you're just running pneumatic tools but I doubt you'll be able to use the air compressor again for spray painting.
I used a fridge compressor as a vacuum pump once but it was hot and messy.
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28th Nov 2017, 09:22 AM #11Most Valued Member
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will take ages
fridge compressors will not carry over anymore oil than any other type of compressor in these circumstances.
Fridge compressors do not make good vaccum pumps...best they can do would be 50000-10000 microns. A good non laboratory vac pump will pull around 150microns.
Now as for the swarf when cutting the hole...if its a reciprocating comp I suggest fitting a connection to the suction line for a future high pressure air connection for latter on.
Turn compressor on side so that your drilling upwards ( as someone said above) once you have hole DO NOT MOVE COMPRESSOR, but now blow high pressure into comp via connection you put in earlier, to remove what crap you can
what remains remains...its will sit at/on the bottom of crankcase for the rest of the compressors life.
If its a rotary comp put the high pressure air connection on the discharge side.
Fit your sight glass and fill with refrigeration oil. such as wax free 46 or 68...not engine oil!!....it will work, but???
dont expect a lot of capacity.
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30th Nov 2017, 05:00 PM #12Novice
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Given you will be drilling into steel, what about a big rare earth magnet stuck to the bottom after you drill it.
Get what you can out, and then use the magnet stuck to the outside as insurance.
Although in reality there's probably a few free fridge compressors out there. What are you using it for? I am assuming you are pressurising a small airbrush or such?
or failing that, if your planning to add a fill point or it already has one, why not use a dipstick instead of a sight glass?
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