Wallies, help with compressed air piping question

Art Pittaway

If the elevation goes up it needs a full size drip leg and drain. Dryer or not, they still carry over water and xxxx? and it's got to be drained. They will be unhappy if the sand blaster gets water on the parts so, like good dry steam, come off the top of the main for air supply and drain the water and oil out the bottom. Put the drip leg about 3' to 4' off the floor and a 1/2" ball valve on the drip leg so they can drain it. Compressed air and steam are NOT plumbing and need to be installed with the idea that there are two things going thru the pipes...air and water!
The few extra fittings will make all the difference to performance.
Best wishes on what sounds like a nice job.
Art

Rocky

Need help with compressed air piping questions.

Contractor friend just asked me to help him with an Army base job he is bidding. My portion is to run approximately 150' of 1-1/2" galvanized sch 40 pipe to be used to carry air from a large compressor to a new sandblasting machine. Run will bend around about 4 corners, have some vertical changes of about 8 feet. What code governs compressed air piping? This will run at pressures of about 100psi. Just checked our 2000 UMC and nothing addressed there about compressed air. Do I have to do anything special with compressed air piping other than just run it? ANY help would be appreciated so I know how to bid this. Its due tomorrow. DOn't you just love friends like that?
Thanks in advance,

Rocky

JimGPE

Not my area of expertise, but

Suggest you call a compressor mfr's rep. They'd be your best source of info if they're any good.

If you don't like his answers, pick another mfr.

Good luck!

Tony Conner

It'll Probably...

...fall under the ASME B31.1 Power Piping Code. (This is the same code that covers steam, if the safety valves lift at anything over 15 PSIG.) Don't look at the operating pressure, look where the safety valve lifts. The operating pressure is for sizing the line, the safety valve setting is for code purposes. Check what they're calling for in the way of pipe. If they say "A53B ERW", don't price "A53F". A53B is a better grade of pipe, and costs more. The same with the fittings and valves - look at what they spec.

Air lines can have some water and/or lube oil in them, so this line should probably slope slightly to the point of use, and should not drop directly into the machine. We drop to the machines, and have a valve above a tee. The branch of the tee goes to the machine (instead of a 90* el), and the other connection gets a nipple and cap. This lets you close the valve, remove the cap, then open the valve to the blow the line out. It they need to do this frequently, they may want a valve instead of the cap, and the isolation valve after the branch from the tee. If we're doing the layout, we have an end-of-main drain, and the machine connections come off the top of the header, if there's room. Somebody already designed this, so you have to bid it as they drew it.

Compressed air is like steam, elevation changes don't matter

Al Letellier

air piping

Sizing goes to CFM requirements. Check with the compressor supplier for proper sizing to the load.
Always run your mains and come off the top. Use a drip leg at the bottom of your drops (just like gas piping). Use a ball valve and plug at the bottom for maintenance blow-down.
use a rated flex connector at the compressor to eliminate vibration in the system.
You can check ASHRAE manuals for sizing, also.
Good luck. And clean your threads well and use good pipe dope!!!!

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Rocky

Air piping

Tony,
thanks for taking the time to respond. I wondered about pitch and what you said makes sense. The plans call for others to make the actual connections to the compressor and point of use device. they just want us to brind it around the wall and terminate it with a ball valve, no drops for service leg or anything. but I think I will make sure I pitch it just to cover my rather ample derierre.
thanks again,
Rocky

Rocky

thanks

Thanks, Al, for the nice input. Pipe diameter was already specified, as well as type of pipe. Don't have to actually make the down drops to the equipment. Just have to terminate the main with a ball valve. Others will make final connections to compressor and point of use device. This is at Ft. Wainwright here in Fairbanks, Alaska. Had to go inspect the site today. This is in a large maintenace hanger. Soldiers there had several 105 mm Howitzers in process of being maintained. Nasty looking pieces of business they are. Sure would want to be on the trigger end of that.
Regards,
Rocky

BillW@honeywell

Air pipe

Unless they have an air dryer after the compressor, water in the lines is inevitable. Try using water/oil removal filters, and avoid running the pipes along cold outside walls. Oil will get worse as compressor rings age, too. An autodrain on the compressor tank helps, too.

Jim Walls_2

Rocky

one thing we have started doing for customers , on industrial air, gas, liquids,etc,,,, is instead of using couplings on long runs install tees with plugs, or if they are willing to spring for a little extra we install a valve. This gives them options down the road for new equipment and many times eliminates down time or overime shutdown situations. Also, & mind you, this may be one of those old plumbing legends , but I was always told to stay away from galvinized air lines as it will flake off and can clog filters. Just a thought. If anyone else has heard of this or knows it to be false please let me know,

Jack_3

bidding job

I did a job for the airforce about 10 years ago make sure you follow the spec to the letter and i do not know about now but back then all the stock had to be american made which is harder to find now then it was back then.
good luck

Jack

Tony Conner

I've Heard...

...of that happening, but I don't know that I've ever actually seen it. In any event, if someone has so much water in the compressed air piping that they need to consider using galvanized, then they need to deal with it back at the compressor and receiver. Ordinary carbon steel A53B pipe should be just fine for normal industrial air lines.

Jackchips

Designed and

supervised many installations and I have never seen or used galvanized. ASPE's data book does not mention it in their design literature either.

ken D

pneumatic information?

Does anybody know any good literature/books on pneumatics?
I'm in the HVAC trade and see it often, but it looks like something I want to run away from, any recommendations, remember, we are to run to problems, not away from them.
Any help is appreciated, especially info you think is excellent, like D.H.'s books.

mp1969

I have done air piping in schools and we always used extra heavy fittings(2000# rating) with drops taken off the top of the main and a drain drop taken off the bottom some where on the run . A looped system is used often to evenly distribute loads.

Rich K.

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Tony Conner

I'd Suggest...

...talking to whatever inspection authority covers pressure piping in your area. (It'll likely be one of the ASME piping codes, and which one applies is usually determined by the service, and type of operation where it's being installed.) They'll be able to tell you (in general terms) what's required, and what exceptions there are, for compressed air piping. These guys typically don't look at the actual function of a system - only things like code compliance, and safety valves, etc. If you need a 4" line, and are only running a 2", they won't care. They'll want to know that you're using the right material, proper joints, hanger spans, etc. It'll probably be the boiler and pressure vessel inspector for your area that will do the pipe too.

For the actual sizing and layout for function, suppliers for things like compressors, regulators, filters, etc often have some good literature. Spirax Sarco at least used to publish "Practical Study" bookets. I have one for compressed air that's from the U.K. It was given to me about 20 years ago, and I've never seen another one, before or since. And it's too bad, because it's really handy. Nothing on code requirements in it, though. That's pretty typical for manufacturers literature. They'll have pressure and temperature ratings on their products, but it's up to you to give them the right info so the component with the correct rating gets picked. Remember that it's the safety valve setting that drives everything for this, NOT the operating pressure. Operating pressure is for sizing the stuff.

Rocky

Wallies, thanks so much for the wonderful insights,

Based on all the great replies I've gotten, I have decided to run the pipe pitched slightly. At the bottom of this pitch, where the mains change elevation, I will install a drip leg with ball valve for blow-down. The schedule 40 galvanized pipe is not my doing. That is what was spec'd on the plans. As well as size (1-1/2" diameter). The plans just called for me to make the main run. Others will make the down drop to the compressor and sand-blaster. However, based on what everyone on the Wall says, I will pipe my mains to make sure that the down drops will come off the top, and that I have a couple drips legs with valves on the main. Even though the plans did not call for this, I think it is the right thing to do, and hopefully, in the future, will get me more work. Would never have known about all the particulars of compressed air piping without the help of all the wonderful contributors to the Wall. Where else on Earth could a guy from Po-dunk, Alaska,
get the benefit of literally thousands of years of cumulative knowledge on this subject? Also, no mention in the plans on if this stuff had to be insulated. I did not bid it for insulation. Any reason why it should be?
By-the-by, this is a large maintenance hanger here on Ft. Wainwright. Had to inspect the job site a couple days ago. Walked into the main maintenance facility, and there were several 105 mm Howitzers in the process of being refurbished. Soldiers doing the refurbishing looked very competent. Wondered to myself if they had orders to get ready. God bless the boys who make the noise.....
Sincere thanks to all who contributed to this post. Am looking forward to getting the job and doing it properly,
Happy Heating ( and compressed air piping)
Rocky

S.D.

Air lines

Don't forget to NOT use oil based pipe dope such as rectorseal #5, oil and compressed air can be dangerous and its even code around here.

Tony Conner

Is That...

...a code requirement in your area for all air lines, even industrial, or just things like medical gas, or breathing air? A lot of industrial air systems have quite a bit of oil in them, carried over from the compressors. I'd have to think that the little tiny bit of oil from pipe dope wouldn't even show up, in applications like that.

Just curious.