Replies

1. 
   UncleDunc | May 17, 2002 04:21am | #1

   Two potential problems, one annoying and one possibly disasterous:

   1. Black iron pipe that's not exactly where you remembered it being will resist a nail or screw. Copper may not.

   2. If you have a small fire in a position to heat one one your joints and melt the solder, then you have compressed air blowing on the fire.

2. 
   BillK68 | May 17, 2002 04:39am | #2

   Bish,

   I am in the process of doing the same thing. For the last 6 years, my Machine Shop business was in a building where we had copper air lines. We never had a problem with them except......we could not keep from getting water in the lines. We tried just about everything we could to no avail. The lines were all pitched to one end, with drains etc etc, but we still always had a ton of water. In the building we had prior to that, we had black iron pipe and never had a water problem...go figure. We are just about finished moving into a new facility and have rubber hoses all over the place until Mr Bill makes up his mind on air lines. I know it is controversial, but I am seriously considering schedule 80 pvc. I have talked to several customers with auto repair shops that are using it with no problems at all. I have found several Air Compressor manufacturers that flat out tell you not to use copper ? They dont say why. I am leaning towards the pcv for ease of installation more than anything. Do some searches on "air compressor pipe" and you will find some information.

   Enough rambling on, other than the water, we had no problems with copper. We had 3/4" through the entire shop.

   Hope this helps,

1. 
   junkhound | May 17, 2002 04:45am | #3

   PVC mfg's specifically say DO NOT use PVC for air.

   Lots of previous threads on burst hazards of PVC, sch 80 or not.

   Just bought some 1-1/4 pvc for water, it is now  printed on the pipe to not use for compressed air.  

   local A/C factories have had copper lines for years, have not heard of problems. Have heard about leaking QC fittings costing upteen thousands of $$ in comp air cost.

2. 
   MarkH128 | May 17, 2002 07:09am | #8

   Copper transfers heat faster than plastic, rubber, or iron. The copper pipe may be much cooler than the compressed air and condensing more water out of the air. I don't know how to correct this problem other than using good moisture separators.

1. 
   DavidThomas | May 17, 2002 05:04pm | #9

   To reiterate what others have said abour compressed air piping: Metal Good. Plastic Bad. Really.

   Condensation occurs in air lines because you didn't get the water out before it got into the lines. A bigger reciever on the compressor will help. So will a lower rate of use. An air to air or air to water heat exchanger helps a lot. Without a dryer, you will always have some water collecting in the lines.

   The heat transfer of copper versus steel is a minimal difference compared to the air films on the inside and outside of the pipe. Plastic does conduct heat less well but eventually comes to room temperature too. Provide drainage/blow-off legs and oversize the piping a bit.

   David Thomas   Overlooking Cook Inlet in Kenai, Alaska

1. 
   AndyEngel | May 17, 2002 07:31pm | #10

   What grade of copper should one use? L? M? K? Anybody know if it matters?Andy Engel, Forum moderator

1. 
   UncleDunc | May 17, 2002 08:10pm | #11

   If you don't have to worry about accidentally nailing or screwing into a pipe, I don't see much point in spending more than you have to. If the pipes are going the be concealed behind sheetrock or whatever, and you're determined to use copper despite my earlier warning :), I would use the heaviest I could get.

   If you look up the specs for the different types, see if you can find a pressure limit specifically for compressed air. It might not be the same as the limit for water.

2. 
   KCPLG | May 18, 2002 02:49am | #12

   Andy

   Most engineers call for type K with silver brazed joints but we have used a lot of type L with silver soldered joints with no problems.

3. 
   bishopbldr | May 18, 2002 03:24am | #13

   Thanks for all the responses. I am planning on all runs being surface mounted so driving a screw or nail into the pipe shouldn't be a problem. All in all I think I'll probably use the copper. If it was buried I'd definitly use iron. Sounds like plenty of drains makes sense also. I also am wondering about having some air outlets with their own pressure regulators, so as not to have to keep changing pressure at the compressor for lower pressure uses such as spray gun, etc. Of course I haven't figured out how to buy the new compressor yet without the wife finding out.  But that's a topic for another thread.

   Bish

4. 
   jimblodgett | May 18, 2002 08:27pm | #14

   "Of course I haven't figured out how to buy the new compressor yet without the wife finding out."

   Just buy her something special first, Bish, like a new belt sander or maybe a new posthole digger. She'll be so pleased about that she won't mind you getting a little something to make your life easier.

3. 
   JohnSprung | May 17, 2002 04:57am | #4

   We have compressed air running in copper all over the Paramount lot.  I don't know for sure how old it is, but the lot's been here since 1926, and some of the buildings involved are definitely pre-WWII.  They have ball valves here and there to blow the condensation out of the lines.  I've heard them do that, and it sounds to me like it could be north of 100 psi, but that's just a guess from the sound.  The most recent change is that they went around sticking labels on the pipes that say "Compressed Air". 

   -- J.S.

4. 
   KCPLG | May 17, 2002 05:23am | #5

   Bish

   Condensation in the line is not the coppers, fault you will stil get it with pvc and as a bonus you get a very hazardous work enviroment pvc can and will shatter I have witnessed the after effects of a shop when the pvc lines exploded. The employees luckily were in the coffee room when they let go, they shattered from one end of the shop to the other damaging vehicles and interior walls the real eye opener was the piece of 2" pvc that put a large dent in the bay door at the front of the shop as the 2" pvc had to travel approx. 30' from the back of the shop. We were there the next day installing copper. By the way workers comp. here will not allow pvc for airlines anymore.

    We install copper and steel waterlines on shops here. Usually engineered jobs so all joints on copper are silver brazed but we have done alot of non engineered jobs with silver solder and have never had a problem. To keep moisture away from your outlets pitch your mains and take your takeoffs for each branch off the top of the line, meaning when you want a branch in a location below the main install the tee pointing up then 90 over then 90 down this way the larger accumulations of moisture will never have a way to get down the branch, it will travel along the pitched piping to your drain, preferably an auto drain as it seems people never remember to drain off the moisture otherwise make it a routine when your turning the lights off and on in the shop that you blow the moisture out also. Hope this helps.

   kevin 

1. 
   jimblodgett | May 17, 2002 05:50am | #6

   Do you just put a valve at the low point in the run?

1. 
   KCPLG | May 17, 2002 06:21am | #7

   Jim

   It's a good idea to put one at the compressor and one at the end of every run if there is more than one run.

   kevin