Propane System - Loose Line Under Motorhome

[sundancev]

Hello all. We have a 39' Fleetwood Providence (2004). Recently while traveling down the highway, we heard a bang/clank. After stopping and looking at motor home and toad, we could find nothing. All tires were at excellent pressure. So, we drove on. Last night while putting our grill away in one of the luggage compartments, I had difficulty closing the luggage compartment door.

I found some kind of gas line that runs underneath our motorhome and exits immediately beneath this luggage compartment door was loose. It appears to be a long copper or metal pipe that runs from the front of the lp gas tank back to this exit point.

Apparently this line is normally secured by some sort of hangers that have failed. The line appears to now be secured only by the front of the LP gas tank and at the exit point below luggage door.

My question: what is the function of this pipe that appears to feed nothing. I am wondering if it is some kind of pressure release equipment in event of tank failure. In any event, I realize I need to get underneath the motor home and some how fasten this pipe to keep it from completely hitting the ground/road as we travel.

Does anyone have a suggestion as to how to fasten. I wonder if this line needs to be level with bottom of tank as it makes it run towards the rear and side of the motor home. I will have to figure out some kind of hanger until I get to civilization. I ask that question due to my former life as a boater, we always had lp gas leak hose at bottom of tank level and exiting the boat in a manner that kept potential fumes on outside of hull.

Any thoughts or suggestions would be appreciated.

Thanks.

Paul

[dickandlois]

Paul, The line is a pressure relief point and yes it connected to the steel rail running under the storage pods.

The rails rust and the screw and clamp holding the line come loose. You will need to reattach it to the rail. If the steel is badly rusted then it will need to be replaced.

This rectangular steel tube supports the storage compartment bay floor or the molded bay compartments.

Rich.

[sundancev]

Rich,

It actually is a copper pipe. Fairly thick. OD is 5/8" inch. I got it loose and found when it dropped it actually bent and partially broke the copper pipe. I was able to remove the pipe by cutting a rubber hose joining two parts (I assume for vibration purposes.) I am going to find auto service place here in Yellowstone and see if I can buy some rubber hose to replace what I took off and rejoin the break.

Interestingly end of the pipe just below the luggage door has a cap which is on pretty tight. Looks like some kind of plastic or rubber cap that has never been off as it does not easily turn. I do not want to put pliers on it and ruin it.

Do you think the purpose is a port simply to remove excess gas that might have inadvertently been put in tank to excess i.e. Last time I was at a RV park in Sacramento, guy put in 28 gallons in 30 gallon tank.

I had read tank should never be filled to more than 80% or 24 gallons. Would that have been the case of when a pipe like this should have been used. This particular pipe does not appear to have regulator. You are also right about rails. I can see where the pipe was fastened to the rails previously.

Thankfully rust is not a problem at hanger points.

[wolfe10]

Paul,

Exactly where on the LP tank does that line originate? Most propane tanks are just vented to atmosphere-- a large diameter hose extending down a couple of inches below the propane tank, which is in a vented/open compartment.

[manholt]

As for hangers, use electric ties or if you don't have that, try rope or tape. Copper in an RV generally = propane. Wonder if it was put in as an option for a gas outdoor grill !?

Carl

[dickandlois]

Paul, This is what I have found regarding the Tanks mounted on RV coaches.

One would hope that the person filling your RV tank would OPEN the vent at the filler point. This bleeds off LP once the tank reaches the 80% point!

Propane tanks.

The line that came loose is a safety line to release LP if the pressure exceeds the upper limit.

Remember ! The Tanks permanently mounted on RV’s are called tanks and not cylinders.

There are a few different safety regulations between the too.

In 1977 the code was changed mandating that the connections, or pigtails, between the propane container and the regulator be made of rubber and then thermoplastic tubing, which would not change diameter in a mechanical "accident," and would activate the excess flow valves reliably when torn apart.

A fiver uses a cylinder; your motorhome uses a tank.

The MH tank is an ASME (American Society of Mechanical Engineers) design and does not require the new OPD (Overfill Protection Device) valves because it already has a check valve and overfill protection, albeit a different design than cylinders.

The ASME Tanks for MHs did not require a change in valve on the tank because they already had sufficient check valves for excess flow, should there be a leak or sudden break in a line. And for more than 17 years, ASME tanks have used automatic stop fill valves to limit filling to 80%. Why so long before DOT cylinders? Because you can't remove them to verify the fill by weight! More importantly, since the connection between the tank and the MHs system is not broken, there is no need for the spring-loaded valve that the DOT cylinders had added with the new OPD valve. That valve prevents the gas from coming out of the cylinder unless there is a tight connection made from the POL or Acme nut depressing the valve. In other words, you can turn on the valve of the DOT cylinder, and no gas would come out unless there was a connector depressing the inside valve. Not necessary for MH connections that are never removed. Thus they were exempted from the OPD changeover rules.

In fact, it is pretty difficult to actually blow up a propane tank or cylinder. What does occur when the pressure relief valve blows, which occurs at 312 psi in ASME tanks, and 375psi in DOT cylinders, is that the gas is vented and makes a lot of noise. I have had one overfilled tank vent and it really got my attention! But there was no flame or problem, as it dissipated outside very quickly. Should there be a fire or source of ignition when it vents, it won't explode either, instead it makes a torch. It does not ignite inside the gas line and run up it to the tank or cylinder and "explode." The only exception to that, is if it is punctured and ignited simultaneously, and then the same external ignition occurs only more rapidly. Or, if a leak is allowed to build up inside an enclosed space like our RVs, and then is ignited, there is one heck of a fire. But oxygen must be present in the right mixture within the ignition range, which is fairly narrow. The important thing is that with the garlic odorant (Ethyl Mercaptin) that is added, you would smell it in most cases of a small leak or break, with time to take appropriate action. It can be smelled by the human nose and your detectors at about 1/5th of the lower limit of combustibility or about 1/2 % propane to air. (Propane combusts at 2.15% gas to air to 9.6% gas to air - not above and not below.) Since most RVs have propane detectors near the floor now, they would alert long before the levels reach dangerous concentrations, if they are in good working order.

An interesting side note is that there are two types of pigtail connector designs to attach to a DOT Cylinder. Appropriately called Type 1 and Type 2. Type 1 is the Acme nut on the pigtail and the OPD valve on the cylinder. Type 2 is a quick-disconnect (QD,) which requires the type 2 OPD Valve that matches it on the DOT cylinder. What makes the Type 2 different from a plain quick disconnect, aside from needing the valve that matches on the cylinder, is that the Type 2 QD has all the safety items built into the pigtail end as the Type 1. This includes the excess flow check valve, and the thermal bushing.

For some reason, unknown to the industry, when the new code was formulated, RVs were left out of approval for the Type 2 valve and pigtail design for a quick disconnect at the cylinder. It is important to note that this part of the code limits only the main connection from cylinder to pigtail to regulator to a Type 1 in RVs. It is acceptable to use a plain propane approved QD for a tap in the line after the regulator in an RV, for example to run a line to a BBQ grill or Catalytic heater.

The line that came loose is a safety line to release LP if the pressure exceeds the upper limit.

Rich.

[sundancev]

Thanks Rich. That is an excellent Treatise on propane tanks. I was able to find some rubber hose at local automotive repair shop and some plumbers/mechanic's tape. I also bought three extra pieces of 3/4" rubber hose to slide down the copper pipe where I then wrapped with the plumbers tape to attach to old holes of hangers that had wasted away. Only final question is the plastic cap on the end of this copper pipe seems to be glued on perhaps due to old age. Should I be worried about that?

Brett, in response to your question, this copper pipe comes from bottom of the tank and about a foot from where it exits the tank, a rubber hose connection was put in, I assume to help with vibration. This copper line now has two rubber connections (2nd one was to join the broken copper pipe.) It does make sense it would be a pressure relief line, but I do not see how it is opened if needed. In other words no valve is present anywhere along the pipe. Whereas the LP line that comes from regulator does in fact have what appears to be a manual valve. I have never used as I typically use the solenoid on/off switch. Thanks Brett, as always you and Rich help us newbies so much. I was commenting to a fellow RV'er today, you have probably saved me $10K over the last five years. BTW, this gentlemen also knows you very well as he participates actively in FMCA rallies.

Best to you all. Paul

[dickandlois]

Posted Today, 09:24 PM

Regarding the plastic cap. You do not have to worry, should the pressure ever get to a level that blows the safety plug it will make short work of the cap!

Rich.

[mpierce]

As for hangers, use electric ties or if you don't have that, try rope or tape. Copper in an RV generally = propane. Wonder if it was put in as an option for a gas outdoor grill !?

Carl

Bingo! I have seen this. Preplumbed to add valve and QD to feed outdoor propane stuff.

[dickandlois]

As for hangers, use electric ties or if you don't have that, try rope or tape. Copper in an RV generally = propane. Wonder if it was put in as an option for a gas outdoor grill !?

Carl

Carl and mpierce! One can add a connection for a grill, but it needs to be installed in the gas line after the regulator.

The line mentioned in Paul's post is a high pressure safety blow off line. There is no LP present under normal operation in this line.

Rich.