Polyethylene or plastic natural/propane gas line above ground 2

[madvb]

Does anyone know if it's a good idea to run polyethylene or plastic gas pipe from under ground and rise above ground to a plug valve before entering a building?

NFPA 3.1.7 says that plastic pipe shall be installed outside and under ground only.... with 2 exceptions:

1. Plastic pipe shall be permitted to terminate above ground where an anodeless riser is used.

2. Plastic pipe shall be permitted to terminate with a wall head adapter above ground in buildings, including basements, where the plastic pipe is inserted in a piping material permitted for use in buildings.

I'm not sure what an anodeless or wall head adapter is. Anyone know what this code is saying? Or have a detail or a website that I can check out?

Thanks in advance.

 

[Montemayor]

madvb:

You ask if it's a good idea to put propane gas in an above-ground plastic pipe. I would tell you it's a rotten idea that is loaded with potential for a deadly accident. In fact, even putting Propane in a U/G plastic line is taking an ill-advised chance, in my opinion.

You quote NFPA 3.1.7 but the NFPA is not recommending you do this. In fact, if you call or contact the NFPA, I'm willing to bet they'll repeat what I just advised you. Propane is doubly dangerous because of it's high relative specific gravity - which allows it to spread to all low sections within an area (especially a building's interior). I also doubt if your insurance carrier will continue your present coverage under prior agreement or contract. What you propose, I guess, is due to an idea of saving a bunch of money on pipe material cost and corrosion maintenance. Why else would you do this? And my experience is telling me that the material cost and corrosion concerns are peanuts compared to the risk and jeopardy introduced by an inherently mechanically weak pipe that is subject to external rupture, solvent attack, and flammable in an external fire or heat source. And I'm not even going to go into the necessary supports, covering, and protection of the PE pipe just to give it some mechanical integrity!

I wouldn't touch this proposal or have anything to do with it. I'm sorry that I have to express myself like this, but I have seen so many mechanical failures of PE and other plastic pipe in mild, water service that I dare not think of doing this for propane in an industrial plant. I've never been known to be a scary cat and have taken a lot of dangerous chances in my 44 years of engineering - but they were all calculated and I had control and a contingency. This type of installation is open for anyone to take his chance at making a mistake - without your control or any contingency.

Regards and hope I have changed your mind.


Art Montemayor
Spring, TX

 

[madvb]

Montemayor,

Thanks for the advice, but your assumption is incorrect... or maybe my question isn't clear enough. I'm doing this project for the Department of Forestry. What they already have at the site is PE gas pipe. Whether the gas is propane or natural gas is different from site to site. Our design is to transition from PE to steel underground and rise above ground with steel and then connect to a plug valve. Anything beyond the plug valve and inside the building is black steel. What Forestry wants is to run PE pipe all the way thru the plug valve. I do not want to rise above the ground with PE because it could easily be damaged. Which is why I looked up NFPA 54, 3.1.7... hoping to find something that will not allow me to rise with PE. Unfortunately the 2 exceptions allow plastic risers. That is my question.... the drawback from having plastic riser. The 2 NFPA exceptions are unclear to me and was hoping if someone has a detail or something similar so I can have a look at. Whether putting PE pipe under ground is a bad idea or not, it can't be changed in this project.... not in the scope of work.

 

[Montemayor]

madvb:

I believe you are correct and smart in trying to avoid putting the PE above ground. That was what I'm trying to have you abort too. What I also am trying to convey is that you don't have to rely on the NFPA to back you up. You should be adament about your stand on a safety issue such as this. Your point is common sense and, in my opinion, the only smart thing to do - you must protect the propane pipe from any potential damage that could result in a dangerous situation.

PE pipe is used in domestic U/G applications - my back yard has a 3/4" LP natural gas feeder to the house meter. As I stated, I would not do the same in an industrial application which is available to all workers and contractors to damage. Backhoe damage on U/G lines (& much more on above ground ones) is a well-known "accident" that has occurred over and over through the years. The last one I saw burned down the plant's transformer building six years ago.

I wish you good luck in making the above ground pipe steel.
Regards

Art Montemayor
Spring, TX

 

[EGT01]

madvb,

A long time past, I did some work for public natural gas distribution systems. I would suggest you contact a local plumber or municpal plumbing supply house for more details.

In the meantime, here's a link to a manufacturer of anodeless risers.

http://www.conind.com/pdf/anodeless risers.pdf

The plastic piping is the actual "container" for the gas. Plastic is not subject to the type of electrochemical corrosion that metal is so the idea is to transition from plastic to metal at a point that the metal "container" won't be in contact with the ground.

The plastic is run through an outer casing of metal which provides rigid support and protects the plastic from external force.