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09-07-2016, 09:27 AM
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#1
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Rivet Master
2016 Interstate Grand Tour Ext
Bellevue
, Washington
Join Date: May 2016
Posts: 689
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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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09-07-2016, 09:41 AM
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#2
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Rivet Master
2011 Interstate Coach
Overland Park
, Kansas
Join Date: Aug 2011
Posts: 2,798
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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.
__________________
Glass half full or half empty to an engineer is the glass is twice as big as it needs to be.
2011 Interstate SOLD! Upfitted 2017 Transit 350. SOLD!
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09-07-2016, 10:07 AM
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#3
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Rivet Master
2016 Interstate Grand Tour Ext
Bellevue
, Washington
Join Date: May 2016
Posts: 689
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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 (788°C), 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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09-07-2016, 10:08 AM
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#4
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Rivet Master
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton
, Arkansas
Join Date: Mar 2013
Posts: 5,868
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OTOH, copper will never rust through.
Gradiens super tenui glacie.
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The fact that I am opinionated does not presuppose that I am wrong......
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09-07-2016, 11:12 AM
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#5
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johnkellygreen
1985 25' Sovereign
Lansdowne
, Pennsylvania
Join Date: Sep 2014
Posts: 10
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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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09-07-2016, 11:13 AM
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#6
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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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).
__________________
I thought getting old would take longer!
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09-07-2016, 12:42 PM
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#7
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Rivet Master
2016 Interstate Grand Tour Ext
Bellevue
, Washington
Join Date: May 2016
Posts: 689
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Quote:
Originally Posted by Protagonist
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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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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09-07-2016, 12:52 PM
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#8
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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Quote:
Originally Posted by amirm
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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No. Hardened expanding foam is closed-cell and will not absorb vapors.
__________________
I thought getting old would take longer!
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09-07-2016, 01:03 PM
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#9
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Wise Elder
2010 30' Classic
Vintage Kin Owner
South of the river
, Minnesota
Join Date: Dec 2009
Posts: 4,169
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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.
__________________
To learn to see below the surface, you must adjust your altitude
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09-07-2016, 02:09 PM
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#10
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Rivet Master
2006 22' Interstate
League City
, Texas
Join Date: Jan 2015
Posts: 698
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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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09-07-2016, 04:18 PM
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#11
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3 Rivet Member
2000 31' Excella
Ontario
, Canada
Join Date: Feb 2010
Posts: 215
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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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09-07-2016, 06:36 PM
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#12
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4 Rivet Member
Currently Looking...
Currently Looking...
Box Elder (formerly Long Island, NY)
, South Dakota
Join Date: May 2013
Posts: 363
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Some cars have PLASTIC / SYNTHETIC fuel lines, NOT steel / metal.
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09-07-2016, 08:22 PM
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#13
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Rivet Master
2011 Interstate Coach
Overland Park
, Kansas
Join Date: Aug 2011
Posts: 2,798
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Quote:
Originally Posted by NY24
Some cars have PLASTIC / SYNTHETIC fuel lines, NOT steel / metal.
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True and I was never a fan of these. Especially since most FI systems operate at > 40 psi.
__________________
Glass half full or half empty to an engineer is the glass is twice as big as it needs to be.
2011 Interstate SOLD! Upfitted 2017 Transit 350. SOLD!
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09-08-2016, 09:50 AM
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#14
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Rivet Master
2016 Interstate Grand Tour Ext
Bellevue
, Washington
Join Date: May 2016
Posts: 689
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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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