ot piping for air

[Mike Stanton]

I am runing 125 lbs pressor and I want to pipe about 40 feet. Can I use type1/2 or 3/4 m coper pipe?

[Jim Becker]

Type "M" is not recommended for this. Yes for Tpe "L" or flexible Type "K". The latter two have much thicker walls. Remember, compressed gasses are different than "water pressure".

[Robert Ducharme]

Definitely use the heavier copper (L). I would only use the flexible underground because it is hard to make it look straight hanging on the wall. Whether or not you should use 1/2" or 3/4" pipe? I would not expect the pipe size to be your limitation in obtaining maximum flow rate. But you should consider what flow rate is needed at the tools and what the compressor can supply. For 40', 1/2" pipe will give you about .63 gallons more air storage while 3/4" will give you about 1.11 gallons more storage. Again, probably not a consideration.

I used 1/2" throughout my workshop and have had no problems. (I am running 175# compressor). My neighbor used 1" steel throughout his.

[David LaRue]

I plumbed my shop with steel. In hindsight It would have been a lot easier to do it with copper.

The issues I ran into with black pipe were:

1) Sloppy tolerances in the fittings (which made sealing at 175 psi a chore)
2) Inability to control the angle of the fitting due to #1
3) Never having the exact length you need (and the store always being out of the size you do need )
With copper these issues are resolved.

Question for the crew: Is there a special solder needed for air / high pressure applications

David

[Kurt Aebi]

Type "L" or "K" copper, make sure you put a moisture trap or stopcocks for moisture removal drains to drain out any moisture in the lines.

[Craig Colvin]

The moisture traps are a necessity. One other thing which was obvious once I heard it but never considered on my own is to make all of the outlet piping face up and have only the drain line facing down. By facing up, little to no moisture can accumulate in the lines.

Another good tip I got for commercial applications was to make the air line a large loop with valves spaced around around each outlet or group of outlets. This allows you to shut off air to a given section to work on it without shutting down the entire air supply.

[Larry Browning]

If type "M" is the thinner walled rigid pipe and type "L" is the thicker walled rigid pipe. I believe that for a home, hobby shop the type "M" is just fine. It is about 1/2 the price of the type "L" and works just fine. Type "L" should be used in a commercial environment. I am using type "M" in my shop with about 135psi and have had no problems. For me price was a huge factor. I saved about $80 buy using type "M".

Larry

PS; This is not OT at all. There are many posts on this same topic in this forum.

[Michael Perata]

I used 1/2" Type "K" copper pipe for a 20' run. Installed easily with a typical torch.

[Brad Schmid]

FYI - Cambridge-Lee Industries has some interesting tables of info on copper plumbing pipe:

http://www.camlee.com/sectors/plmb/p...g_products.htm
http://www.camlee.com/sectors/plmb/plumbingspecs.htm

These tables show internal working pressures for each type (both annealed and drawn) as well as recommended uses for each type.

Type L specifically has Natural Gas applications listed so that's probably the best choice if I read this right. However, 1/2" type M has internal pressure ratings of 410psi (annealed) and 760psi (drawn) which would seem more than adequate.

Would be interested to hear other thoughts.
Brad

[Jim Becker]

Brad, are those pressure ratings for liquids or gasses on the type M you are citing?

[Steve Stube]

Jim, both (liquids and gasses) according to the link he provided.

http://www.camlee.com/sectors/plmb/plumbingspecs.htm

[Steve Stube]

Jim, I think I feel your concern regarding the type "M" tubing and I will agree with you if you are opposed to using it for pressurized air lines - I wouldn't use it myself. Reasons; in 3/4" you don't even have a safety factor of 2 when using a two stage compressor pumping at 175 psi. (it's 350 vs. 325) further any slight mechanical damage such as a dent or abrasion can jeopardize the integrity of the installation or worse. If you think you might be involved in an accident, drive something a little beefier than Hugo (can I say that).

[Brad Schmid]

Brad, are those pressure ratings for liquids or gasses on the type M you are citing?

Jim,
Incidentally, at least in the working environment, there is no difference whether the pressure is exerted with gas or liquid, the same force is exerted on the internal surface area of the pipe regardless of substance. So I believe this is reflected in the documentation on this manufacturers site. Now, in a braniac lab environment, there may be some subtle differences, but that's not my gig, so I won't comment.

Don't get me wrong, personally I too would prefer to use Type L for the additional safety margin with gas (air), but then I'm way over cautious about pressurized tubing from working in the Oil and Gas Industry for a long time where it is phenomenally destructive. Really, the difference in gas vesus liquid (specifically water) is that gas is a compressible fluid, wheras water is not. In other words, if you exceed the rating of the pipe with water and it bursts, there would not be an explosion or violent reaction of any kind, just a leak. With gas, it would be a giant pipe bomb. I'm also with Steve in that if there's a possibility of one of these pressurized lines being damaged by an external force, better off to be safe with a heavier type pipe rated for gas.

In the Oilfield services industry, we often work on extremely high pressure gas wells that require us to attach "riser pipe" to the wellheads to enclose tool strings to run in a well. We are required by law to test this riser gear periodically, and the OSHA approved method of testing it is to pressurize the gear with water to a maximum pressure based on the rating of the equipment. It is a very safe way and if you've ever done it, it proves to you just how uncompressible water really is. You can go from 0 psi to 10,000-20,000 psi on several hundred gallons of water with a few pumps of a hydraulic hand pump. Compare this to how long it takes to pressurize your air compressor

So, bottom line, this thread just got me thinking... that's all. I may even contact a manufacturer just to see what they say. By ratings alone, it would appear to be safe to use 1/2" M in a standard 125psi homeshop system, but I would never recommend that without talking with a manufacturer. Sorry so long winded...

BTW - we hadn't discussed soldered joints... I wonder about those...
Cheers,
Brad

[Jim Becker]

Brad, isn't the difference that liquids don't "compress" but gasses do? (I'm only asking to learn something...)

[Brad Schmid]

Update:

Curiosity got the best of me and I called Cambridge-Lee whose corporate HQ is in Reading, PA. I talked to one of their engineers on the phone and here is what he said:

For 1/2" Type M drawn copper pipe (this is what you buy at any home center)

- up to 100 deg F rated internal working pressure is 850psi, drops to 825 psi at 300 deg F. (these are different than the chart, but I didn't realize it until I had already hung up the phone)

- 50/50/10 lead solder joint is rated at 200 psi at 100 deg F. 95/5/10 antimony (he says most commonly used today) solder joint is rated at 635 psi @100 deg F

- he did not have rating info on compression type joints

My final question was: is it safe to use this in a standard 125 psi compressed air home shop environment? His answer "yes, but personally he would use Type L". Read into that whatever you want

To me, it seems you really need to be concerned as much with the solder joints and the type of solder you use no matter what type you use. It will always be the weakest point.

If you're going this route I would encourage you to give the manufacturer a call and ask some questions. I certainly learned a few things.

Hope this helps,
Regards,
Brad