Compressed Air Piping-Material? 2

[kepharda]

I am working on the piping design for a small production facility. The Process Engr. who is in Switz. constantly suggests to the manager to do things that may work, but are not in my mind very prudent.

The latest is that he wishes to utilize Carbon Steel pipe for an Instrument Air Piping System. He has suggested (rather strongly) that I don't use copper or stainless or even galvanized piping.

My obvious concern is corrosion in the line causing problems downstream in the sensitive instruments and actuators? Is my concern misguided?

thanks all suggestions,

dave

 

[katmar]

I have seen galvanized IA piping that has lasted for years. I suspect that the galvanizing was more to protect the piping externally because the plant was only a mile or 2 from the sea in a very humid environment. This was in an ethanol distillery.

In my experience thin walled (2mm) stainless is becoming more and more competitive with standard wall CS when considered on a life cycle basis, but I have not used it for IA myself.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[kepharda]

I agree katmar, now that I am thinking about it the last time I used galvanized for compressed air it was in a titanium plant, they have all sorts of nasty corrosive stuff in the air when in operation.

I saw a production worker at this plant accidently kick a Building Column, and large chunk of the web just broke away. Luckily we were there to demo and rebuild the building anyway but still pretty impressive.

thanks,

dave.

 

[mizzoueng]

Either can be used. I have used copper, CS, and SS for IA piping in the past. It all just depends on what conditions you have.

Looks like you got it figured out though, if the copper is already there and the owner likes it, then go with that. You could argue CS but unless there are filters at the IA conenction, then I would shy away from it. The times that I have ran CS in IA applications, it was for headers and branches, once at the IA connection and after that SS or copper was ran.

 

[dcasto]

Here's one for y'all to ponder. We installed a buried I/A line that was over 12000' of 2". We specified PE pipe. The PE manufacturers stated that we needed to derate the PE 50% because of oxygen attach at pressure on the PE! Went to the next ticker material as it was still cheaper than steel. Derate PE for air???

 

[Ben4piping]

Victaulic Pressfit is 2" and smaller sch 5 in carbon steel electrogalvanized. Also 304 and 316 SS are available. Pressures to 300 psig. My former workplace used it a lot. The SS was preferred for IA service (but not at coastal sites).

Ben N.

 

[kenvlach]

Plastic piping for compressed air in workplaces is illegal per OSHA unless certified suitable by the piping manufacturer. I only know of 2 'specially engineered grade' ABS piping for compressed air:
CHEM-AIRE® from Nibco:

http://www.nibco.com/assets/ChmairTech.pdf

and
Duraplus™ from IPEX. IPEX also has a HDPE/Al/HDPE composite piping (Al tubing clad inside & out) called DURATEC, mostly for corrosive environments:

http://www.ipexinc.com/Content/EN_US/2_0_Products/2_1_Industrial/2_1_4_Compressed_air.asp

OSHA Hazard Information Bulletins
The Use of Polyvinyl Chloride Pipe in Above Ground Installations.

http://www.osha-slc.gov/dts/hib/hib_data/hib19880520.html

My experience is with the green CHEM-AIRE® -- really easy to use, like any other solvent welded plastic. Also, 'Chem-Aire systems meet all requirements of California OSHA Standard. “Plastic Piping Systems for Compressed Air” Title 8, Chapter 4.'
Caveat: The ABS is incompatible with some compressor oils. No problem if you use a 3-in-1 dryer to produce clean, oil-free dry air for painting, instruments, parts drying.

 

[moltenmetal]

kenvlach: thanks for mentioning the ABS piping products.

Plastic airline tubing, as opposed to piping, is sold by the thousands of miles yearly for industrial compressed air applications. PE, nylon and polyurethane are all widely used.

 

[pvcman]

Man, What a bunch of metal heads. Duraplus Airsystems and the new duratec coiled system for 1" and down.
250 psi compression joints small bore and 2" and above solvent weld coiled system is hdpe encapsulated aluminum. cost a fraction of copper and clean (no metal pits) so filter requirements are almost null.
Check out

http://www.harringtonplastics.com

 

[kepharda]

Plastic can work for some systems, however, must be derated for anything above ~70 F.

Therefore it can be a problem around alot of equipment in a industrial environment.

Also, UV can be a problem with any polymer.

There are applications for metal, we aren't all idiots.

Regards,

 

[pvcman]

I really didn't mean to make a mean joke (metal heads) but you are wrong again. Not all plastics have to be derated @ 70 deg.I really do agree some plastics are limited to both temperature and pressure. Consider 60% of plant air is 150 psi and below running at ambient temp. Indoor.
So the UV issue other than lighting is not an issue and the temperature on some plastics are 300deg. F
Cleaner /no pitting /no corrosion due to condensate/virtual mtc. free/ inside as well as outside /light weight less stress on beams and supports. There are many plastics systems out there that will do a fantastic job.You just have to engineer these sytems different that metals.

 

[rconner]

pvcman,
Whether or not it was meant as a compliment your introductory statement might not really "be a way to some (experienced engineer's) hearts"! While I don’t have enough experience with same to gauge utility I was just curious also if the piping you describe is like what has recently sometimes been used with couplings or fittings such as I saw today described in a news article at

http://www.reviewjournal.com/lvrj_home/2007/Feb-09-Fri-2007/business/12368182.html

and

http://www.reviewjournal.com/lvrj_home/2007/Feb-09-Fri-2007/business/12368182.html

(though in that case for water service application)? I was just curious also would your plastic pipe/tubing be more tolerant of heat/fire or less exciting than say steel or ductile iron or if/when? a forklift tine or lifted piece of equipment impacts/gouges into it or in a heat/fire event?

 

[kepharda]

How exactly was I wrong?

Also, I looked at the site you mentioned and all the pipe I saw in the online catalog was rated either 180 F or 230 F and all needed to be derated at temps above 73 F.

I don't know about most of the places you design in, but most industrial applications are above 73 F.

I am sure you are a great saleman, but you can't tell me I am wrong when I wasn't

Plastics are fine, I have used them before, but your attitude is offensive.

 

[kenvlach]

pvcman,
Please show good manners by reading threads before posting.

Also, regarding your post:

...solvent weld coiled system is hdpe encapsulated aluminum.

Please explain how Duratec is solvent welded. Is the HDPE or the aluminum welded, or both?

 

[rconner]

Oops (I saw I accidentally repeated the same link in my post -- the site I noticed after seeing the news blurb yesterday is at

http://www.plumbingdefect.com/product.php)