Shop realities

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John Hasler
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Re: Shop realities

Post by John Hasler » Tue Nov 06, 2018 9:16 pm

SteveHGraham wrote:
Mon Nov 05, 2018 6:51 pm
Common sense suggests that 17.5 CFM means you can run the pump without a tank at typical compressor pressure (maybe 100 psi) and get 17.5 CFM without losing steam. I am not a compressor engineer, however.

Your post reminds me why I hate imperial units.
CFM always refers to uncompressed volume. It's effectively the rate at which the compressor takes in air.

The correct metric unit is the "normal cubic meter per second" but you will probably actually see liters/minute.

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liveaboard
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Re: Shop realities

Post by liveaboard » Wed Nov 07, 2018 5:11 am

Long ago when I was working at a car repair garage in the US, my boss had an air powered grinder.
I don't remember the brand, but knowing him it would have been a good one.

That thing would drain our 5HP shop compressor 3x faster than it could recharge; and the grinder definitely wasn't 5 hp, let alone 15.
Also, the air expanding through it would make it go ice cold [further reducing efficiency of course]. Meanwhile, energy was being converted to heat at the compressor head. The inefficiency of it all was just amazing.

We had little air drills that seemed to work ok, but basically I prefer electric motor tools.

John Hasler
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Re: Shop realities

Post by John Hasler » Wed Nov 07, 2018 9:28 am

The only advantage of air tools over electrics is power density. They are losing that edge as motors get better.

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wlw-19958
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Re: Shop realities

Post by wlw-19958 » Wed Nov 07, 2018 12:16 pm

Hi There,
John Hasler wrote:
Wed Nov 07, 2018 9:28 am
The only advantage of air tools over electrics is power density. They are losing that edge as motors get better.
How about when working in a wet or hazardous environment?

Good Luck!
-Blue Chips-
Webb

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liveaboard
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Re: Shop realities

Post by liveaboard » Wed Nov 07, 2018 1:56 pm

You might get power density; someone will have to do some testing to work that out; difficult as power claims by tool makers can be fanciful.

On the negative side, those tools will only work in your shop, at the limit of your air hoses. Your electric tools don't work everywhere either of course, but they work in many more places than the air tools.

Wet / dangerous; for the last 20 or 30 years, we've had GFI [ground fault interrupter] breakers. they pretty much eliminate the danger of electrocution, and although nuisance trips can be a pain I'm quite fond of them.

Of course air tools don't spark, so in explosive environments they have a real edge.
If I start mining or refining gasoline, I'll definitely go air.

John Hasler
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Re: Shop realities

Post by John Hasler » Wed Nov 07, 2018 2:53 pm

Short of immersion double insulation plus GFIs takes care of the wet. You're right about hazardous areas. Electric motor power density in tools and other small motors is going to increase substantially as brushless motor technology takes over. The claims made by marketing firms are irrelevant, of course.

rrnut-2
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Re: Shop realities

Post by rrnut-2 » Wed Nov 07, 2018 4:24 pm

For air piping, I put this into my shop https://www.northerntool.com/shop/tools ... _200484023. I would recommend if anybody is considering it, throw away the instructions. If you follow the instructions, the joints will blow apart when you least expect it. For instance, I was doing a milling operation and concentrating on precise work...a very load explosion....I jump about 3 feet...work is ruined! I had to go back and use never seize on every connection and It still leaks. The connectors are stainless steel.

Jim B

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liveaboard
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Re: Shop realities

Post by liveaboard » Wed Nov 07, 2018 5:45 pm

I used PEX, the same as the plumbing in my house. I used loctite string on threaded joints.
No leakage and so far nothing has exploded.

rrnut-2
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Re: Shop realities

Post by rrnut-2 » Thu Nov 08, 2018 6:40 am

Oops! I meant to say that I would NOT recommend this stuff that I used for air line.
https://www.northerntool.com/shop/tools ... _200484023

Jim B

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