Where to Mount Propane Tank?

[TomC]

I have my chassis mounted 100# propane tank mounted under my transit bus with nothing under it. So venting is a givin.  I know this is acceptable since vertually every propane powered car I see also has nothing under the bare tank. 
I have never heard of having to vent your propane tank up 6 ft from the ground. Since propane is heavier than air-what's the reasoning?  Good Luck, TomC

[jackhartjr]

Hi Tom, you said; "Since propane is heavier than air-what's the reasoning?" 

That is exactly why it needs to be vented; because propane is heavier that air...if there is a leak...the propane will go down...if it has no escape...it builds up in the bays..then a spark can ignite it.  That is why it needs to escape down to the gound...that way it usually dissipates and is no problem. 
In a bus with the bay doors closed I could imagine an explosion could send the bay doors straight out a half mile to a mile.

Jack

[Chaz]

Jack,
  The question is, why does it need to be vented 6' UP? I think Tom is very aware it will settle to the bottom and if the vent is so far up, how can it do any good?? I am wondering the same thing.
   Chaz

[jackhartjr]

Hi Chaz...I don't know about the 6' up thing...all I know is that the propane is heavier than air and will go down.
Can someone 'edgumacate me on the 6' thing?
I hope nobody makes me drag out the propane regulations, as I recall it is a big big book!
Jack

[jjrbus]

My guess is the 6 ft is for the overfil/overpressure vent? Not an issue with portable tanks.
I also have a quick disconnect and 20 foot hose for the grill and 2 burner cooktop, I do not like to cook fish or greasy foods inside.
To have the LP truck fill my  30lb tank at this campground in FL it costs $24. Down the street it costs $18. Now I know you rich guys are saying I would not haul my tank around for a mere $6. But for us senior citizens on fixed incomes its a big deal. Besides I'm cheap and proud of it!!

[JohnEd]

Chaz,

Amigo...The main pipe in my Winnie is a "Black Iron Gas Pipe" that is related to military armour.  My tanks connect to it and the appliances have a separate connection each.  It is located outside and up inside the frame rails above the drive shaft.  That is the ONLY pipe I would use to run gas down a bus.  Every device and length of pipe is a failure point and with gas all failure points are "critical failure" points.  An extra ten feet of black iron isn't much of a bump in the failure direction unless you are taking mortar fire.

As I understood it: the venting of the "overfill" burp valve to the tank space would mean that that large quantity of gas was being deposited directly under the vehicle.  It makes sense to me that i would want to avoid that situation.  I surmise that the 6 foot rule was so that the gas would disperse more rapidly as it "fell" to the ground.  Also, it would interupt the trail of gas back to the PROPANE COMPARTMENT.  Now I swear to you that I am not making this up and it IS NOT MY LIE.  I read it and it was supposed to have come out of the "book".  At the time it was noted that none of the highlines with permanent tanks followed this "rule".  Now if some yutz overfilled my 100 gallon propane tank by a couple gallons it might take a day for that to pop off from warming.  I DO NOT WANT 2 GALLONS of propane in my locker regardless of how many holes I have in the floor and I also do not want that UNDER MY BUS or leaving a trail back to the point of origin(me and mine).  There is no class of fire extinguisher that puts out 2 gallons of propane till that stuff is good and ready to be put out.  The pressure relieve valve has a screw on defuser and I will run that to the exterior of the bus....probably 6 ft high at the rear.  Color me superstitious, anal retentive or peculiar......1/4 inch copper tubing?? gahwan!

This was fun,  Drag out the regs Jack...please

John

[Chaz]

Color me superstitious, anal retentive or peculiar......1/4 inch copper tubing?? gahwan!

Whatever.

[DavidInWilmNC]

I'm curious... has anybody owned, or even seen, a S&S motorhome that has the built-in tank's overfill valve vented 6' up and at the rear?  The ones I've seen have the tank strapped underneath, open to the ground, with an access door to the fill port, regulator, level gauge, etc.

David

[kyle4501]

In my experience with propane, whenever you have uncontrolled ignition of a leak, the combustion of the propane is over by the time you notice what caused the ringing in your ears. All that is left is to put out the burning combustables of the aftermath & pick up the pieces.

Propane must be mixed with air in the right ratio in order to burn. If it is too rich, it will only burn at the boundary where it can get enough air. If it is too lean, it just won't burn.

My guess about the 6' rule has to do with 'normal' venting & allowing it to go lean enough before it puddles to minimize the danger.

Concerning the long run's of gas line in a coach - There is a good reason the code requires exposed black iron for the main run. do you think it might be because it is tough enough to tolerate most abuse & so inspections can be made to ensure the integrity of the system.
Yes, propane can be dangerous - just like any stored energy. If it is handled properly, the benefits outweigh the risks.

BTW, I've known more people to be hurt by compressed air than propane. ANY stored energy can bite if you get careless.

[jackhartjr]

David, I am pretty sure it has to do with the size of the tank.  I know the 100's have to be vented like that, (I think, there's that word again...think...!  I am trying to find the regulations, I know they are here somewhere, I moved in May after getting married, still sorting it all out!
Like I said, I intend on going to the regulations and will post what I learn.
The reason I jumped in here is that on one of the sailboat forums I post on there were two reports of boats being blown to smithereens this year due to propane leaks that settles in the bildge, a switch was thrown and it was horrible!

Here is a link to one of them.

http://archives.sailboatowners.com/pviewarch.htm?fno=60&sku=2007221055435.41&id=490589&ptl=Terrible%20Accident&id=490589

As I recall they later reported this man died a week later.

On the other on a group of schoolgirls had gotten off the boat a few minutes prior...can you imagine!?

Jack Hart

[Tenor]

An interesting idea I saw on an MCI 9 was one or 2 20lb's in the old air conditioning condenser bay.  Since the door is almost entirely  screen and there are already vents out for the old blower, it seems like an easy way to go.  He had his genset in the first bay on the drivers side and also drew air in for the radiator through the ac compartment past the tanks using a wood shroud to direct the air.  I am likely to do the same.

[JohnEd]

Kyle,

Good points all.

Jack,

Please post the results of your quest.  I don't think anybody ever said a portable tank had to be special vented....only those big stationary ones, as you said. 

Thanks,

John

[TomC]

I have seen natural gas buses with the over pressure blow off-looks like a small exhaust pipe-coming out of the roof at the rear.  But I haven't read or heard about that being needed for propane.  Good Luck, TomC

[JohnEd]

TomC,

Boogiethecat has a post reply titled "are your propane tanks vented".  In that post it mentions that LNG, being lighter than air, is vented at the "top" rear corner of the bus.  Propane is vented in the rear but not so high as I take their discusion.  Again, I think this only applies to fixed tanks, mounted inside the bus and of a specified "larger than" size.  Again the comment was made "you don't want a large quantity of fumes POOLING under your bus.  Hope jack finds the reg.

sincerely,

John

[JackConrad]

Not sure about the venting regs, but natural gas is lighter then air and will rise, LP is heavier than air and will settle. That is why we (the Fire Department ) were always more concerned about propane leaks as the propane would pool in low areas and no way to contain it.  Natural gas would rise into the air and dilute itself. Jack