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Old 09-07-2016, 10:27 AM   #1
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LP lines: is this really safe???

As I finish my surgery of my Interstate for Lithium conversion, I often come across questionable practices. One that was very surprising was underneath the body. I was there pulling out the old battery and rewiring the generator and noticed this gas distribution line that goes to the water heater inside the cabin:



First thing that scares me is the lack of any protection for the copper tubing. Is this a rock away from puncturing?

Second, they have pulled this above the leaf springs. The chassis actually has a round over to give more space for the springs to travel upright. Airstream has run this copper LP feed and the ground wire through that space. Not being a mechanic and I don't know if all of that clearance was needed or not. Does anybody know?

And is there a safer way to run gas pipes? I noticed that the feed to and from the external connection for filling it uses some kind of rubber/hydraulic line instead of bare copper.

If there is one thing that has always scared me is having all of this LP gas and feeds under the vehicle! Sure like to make this as safe as possible. Appreciate any advice/comments.
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Old 09-07-2016, 10:41 AM   #2
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There's a reason that cars use steel fuel lines instead of copper. From what I've determined it's because copper can "work harden" and become brittle when subjected to heat and vibration.

I was concerned also the first time I saw the copper lines used for the propane. The safer way would be to use steel lines.
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Old 09-07-2016, 11:07 AM   #3
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Thanks. Found this in NFPA 1192:

5.4.2 Gas Piping System Materials. Materials used for the installation,

extension, alteration, or repair of any gas piping system
shall be new and free from defects or internal obstructions. Inferior
or defective materials in gas piping or fittings shall be replaced
and shall not be repaired. Inferior or defective materials
shall be removed and replaced with acceptable material. The system
shall be made of materials having a melting point of not less
than 1450
F (788C), except as provided in 5.4.5, 5.4.6, and
5.4.12, or of materials (used in piping or fittings) listed for the
specific use intended. Gas piping system materials shall be permitted
to consist of one or more of the following materials:
(1) Gas pipe shall be steel or wrought-iron pipe complying
with ASTM A 53, Specifications for Pipe, Steel, Black and Hot-
Dipped, Zinc-Coated Welded and Seamless. Threaded copper or
brass pipe in iron pipe sizes shall be permitted to be used.
(2) Fittings for gas piping shall be wrought iron, malleable
iron, steel, or brass (containing not more than 75 percent
copper). Brass flare nuts shall be stress relieved or of the
forged type.

(3) Copper tubing shall be annealed Type K or L, conforming
to ASTM B 88, Standard Specifications for Seamless Copper
Water Tube, or shall comply with ASTM B 280, Specifications
for Seamless Copper Tube for Air Conditioning and Refrigeration
Field Service. Where used on systems designed for natural
gas, copper tubing shall be internally tinned.

So looks like copper is allowed. Question is whether they used this type or not. And at any rate, how one would retrofit. There T-splits and such feeding generator and other bits with compression fittings. All using the same small diameter copper tubing.
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Old 09-07-2016, 11:08 AM   #4
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Old 09-07-2016, 12:12 PM   #5
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The gas lines are run on the underside of the Airstream to allow any gas leakage that may occur, to dissipate in the open air. An internal leak could have dangerous consequences. I'm sorry that I can't speak to the rock hazard. Sorry.
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Old 09-07-2016, 12:13 PM   #6
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Type K copper tubing has the greatest wall thickness, and usually has green labeling printed on the tubing. Available in soft-tempered or hard-tempered. You want soft-tempered.

Type L is thinner (but still thicker than Type M) and usually has blue labeling printed on the tubing. Available in soft-tempered or hard-tempered. You want soft-tempered.

Type M (not allowed) usually has red labeling printed on the tubing. It's available in hard-tempered only.

The LPG system on an Interstate is a low-pressure system; the regulator is located at the ASME tank. Also, all joints in the LPG plumbing are located outside the inhabited spaces of the van (i.e. underneath), so that any leaks at joints are to outside where the propane can dissipate without ever reaching the lower explosive limit (LEL) in air.

As for the placement of the line in the photograph, note the proximity to the bushing at the end of the spring. This geometry ensures that the copper tubing cannot be crushed between spring and frame unless the bushing is destroyed first, meaning that you'd have bigger problems than just a propane leak. It's actually a very safe location for the tubing.

If you're concerned with thrown rocks puncturing the copper tubing (on the Alaska Highway, maybe?) then it would be a simple enough matter to cable-tie slit plastic tubing around the copper tubing to act as a rock guard. Leave a gap at each joint in the copper tubing, though. It's best to use plastic hose of the same or slightly smaller diameter so it doesn't quite wrap completely around and doesn't form an enclosed space for propane to accumulate if a leak does occur.

I would not recommend encasing the tubing in foam pipe insulation. In the event of a propane leak, the leaking propane could saturate the foam and make it very flammable (i.e. like a matchstick).
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Old 09-07-2016, 01:42 PM   #7
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Quote:
Originally Posted by Protagonist View Post
I would not recommend encasing the tubing in foam pipe insulation. In the event of a propane leak, the leaking propane could saturate the foam and make it very flammable (i.e. like a matchstick).
Thanks for the informative post as always . On this, the ingress to the cabin is through a large hole that is then filled in with expanding foam. Do you feel a similar issue here? The total length so covered is about 5-6 inches.
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Old 09-07-2016, 01:52 PM   #8
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Quote:
Originally Posted by amirm View Post
Thanks for the informative post as always . On this, the ingress to the cabin is through a large hole that is then filled in with expanding foam. Do you feel a similar issue here? The total length so covered is about 5-6 inches.
No. Hardened expanding foam is closed-cell and will not absorb vapors.
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Old 09-07-2016, 02:03 PM   #9
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amirm,

The practices you see are customary, although RVs made for export to Canada have the copper tubing sleeved with PEX to provide additional abrasion resistance.

Type K copper is an extremely tough material. Under enough pressure it will kink resulting in a blockage but it is very difficult to puncture. As Protagonist points out, propane leaks under the chassis rarely result in a serious safety problem since the gas will dissipate before reaching the LEL.
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Old 09-07-2016, 03:09 PM   #10
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On our older Interstate, the most exposed copper lines were run inside of PEX tubing and sealed on the ends with plumbers putty.
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Old 09-07-2016, 05:18 PM   #11
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I agree with what info has been provided. Put a sleeve around the exposed pipe to save pipe from stone hits. easy to do and safer for you. Also you will have exposed piping joints about the floor but as long as these are properly installed an tested, it's not a problem. also propane stinks so any leak should be smelled and every rv that has propane has those little boxes with flashing lights to let you know system is safe.
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Old 09-07-2016, 07:36 PM   #12
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Some cars have PLASTIC / SYNTHETIC fuel lines, NOT steel / metal.
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Old 09-07-2016, 09:22 PM   #13
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Quote:
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Some cars have PLASTIC / SYNTHETIC fuel lines, NOT steel / metal.
True and I was never a fan of these. Especially since most FI systems operate at > 40 psi.
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Old 09-08-2016, 10:50 AM   #14
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Thanks everyone. I am a "belt and suspenders" kind of guy when it comes to safety . Your posts put my mind at ease somewhat but I might at some point put the pex cover on them. Right now, I am too miserable from upgrading the wiring that was there!
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