I made a sealed box for a 20LB propane tank

[One Awesome Inch]

Video:

I made a sealed box for a 20LB propane tank

 

[akrvbob]

We need you to put up something besides a youtube video link, otherwise you are excluding a large group of members.

Pictures are best but a description will do.
Bob

 

[One Awesome Inch]

Understood.

Basically the video shows my design and construction of a sealed plywood box. I could not find a decent video of how to construct one.

Access to the on/off valve is thru a gamma seal lid. I can remove and replace the tank via one of the panels that comes off. I used T nuts under strips oak for stiffness. The panel/door is attached via bolts that are screwed thru the door and into the T nuts. Between the door and the ply box is a gasket made of 3/4 inch weather stripping. Its purpose is to keep the box air tight.

I'll post some pics when I get wifi again. Probably tomorrow night.

 

[akrvbob]

Are you going to vent the box?
Bob

 

[highdesertranger]

Are you going to vent the box? my thoughts exactly. highdesertranger

 

[One Awesome Inch]

Yes, I will vent it via a hole I drill through the bottom and through the van's floor. Probably have to use some tubing or pvc pipe to keep things airtight.

 

[eDJ_]

Just a thought here.

I can tell you put a lot of time and effort, not to mention thought into this.  And I think it is a nice bit of work too.

But on the vent going out through the bottom, will it be large enough in diameter to allow for both the heavy
LP going out  to allow fresh outside air to be pulled into the box from outside to assure a flow of ventilation air ? 


That design issue stuck with me watching your presentation.

What could I offer as a solution ?   Perhaps a tube in the bottom that goes through the hole in the floor of the Van would have a smaller tube inside that would extend up into the box a couple inches or so.  Thus the heavier
LP draining out would siphon fresh air into the box to assure positive circulation.  Then if a 2 inch tube were
to be used it may be of large enough diameter by itself to allow the LP to drain while fresh air is pulled back in. 

I've noticed some of the plastic necks on my lawn mower gas tanks use this feature.  A small tube is molded
inside the plastic neck to assure positive ventilation.  I know the gasoline is a liquid and all but the idea is the
same.

......and believe me I know how hard it is to get projects like that "spot on" perfect the first time out.

 

[Optimistic Paranoid]

I'll just add one thought;  I would be sure to screen the drain to keep vermin from entering the box from the outside.  I would use a bit of insect screening to keep out small bugs, and reinforce it with a bit of that 1"x1" hardware stuff that  mice can't chew through.

Regards
John

 

[Optimistic Paranoid]

What could I offer as a solution ?   Perhaps a tube in the bottom that goes through the hole in the floor of the Van would have a smaller tube inside that would extend up into the box a couple inches or so.  Thus the heavier
LP draining out would siphon fresh air into the box to assure positive circulation.  Then if a 2 inch tube were
to be used it may be of large enough diameter by itself to allow the LP to drain while fresh air is pulled back in. 

An excellent thought.  However, the specs for approving a propane locker on boats requires that the air intake be located ABOVE the level of the valve on the cylinder.  I would suggest a separate tube in one of the corners that also exits through the floor and goes almost to the top of the box.  Also screened, of course.  Perhaps a 2" pipe for the drain and a 1" pipe for the intake.

Regards
John

 

[One Awesome Inch]

Some good ideas there.

I'm apprehensive about cutting 2 inch holes in the floor of the van.

Could I do the outtake / short one with a 3/4 circumference and the tall intake with a 1 inch circumference?

Would that be sufficient for airflow?

 

[Optimistic Paranoid]

Well, here's the site I was looking at:  http://www.boatsafetyscheme.org/media/164540/bss guide chap7.pdf

They seem to feel that 12mm (1/2 in) would be adequate as a drain for a 20 lb. cylinder.

Personally, I would think that bigger is better, but they're the experts.

Regards
John

 

[Almost There]

Keep in mind that air flow is quite restricted the minute you add any kind of bug screening.

I haven't measured the exact reduction in air flow but I can tell you from sleeping inside a bug net in the hammock that it is fairly substantial.

To overcome that, I'd suggest a much larger pair of vent tubes than the minimum.

 

[Spaceman Spiff]

Keep in mind that air flow is quite restricted the minute you add any kind of bug screening...

 but I can tell you from sleeping inside a bug net in the hammock that it is fairly substantial.

To overcome that, I'd suggest a much larger pair of vent tubes than the minimum.

'No-see-um' netting on a hammock is much more restrictive than standard window screening.  For laminar flow window screen is <10%.  Since propane is heavier than air, it will be instructive to think of how your container would drain if filled with water.  Propane will act the same, only more slowly.  Note also that the 'boatsafety' guide only have one drain (in the bottom) on a sealed locker.  Any leaked propane will find its way out in short order, no need for intake.

One thing to keep in mind: keep well away from any heat sources if you are exhausting propane under the van; spectacular results could happen.

-- Spiff

 

[eDJ_]

After reading all of this,  I was just wondering if a piece of common furnace filter on the end of the tube under
the Van would serve to keep insects etc out and at the same time allow the LP to pass through it.

Secondly,  where the hose comes out of the top.  Don't seal it.  This may allow enough air to enter
as any LP is flowing out.

This kind of filter media in blue:  One filter would certainly provide enough and a simple nylon zip tie
may hold it in place well enough.

 

[One Awesome Inch]

Id feel alot more comfortable sealing up the propane hose hole. Its supposed to be a "sealed" box.

Also, are you guys *sure* I only need the outtake hole and not the intake?

I'm drilling holes here people!

 

[Spaceman Spiff]

Id feel alot more comfortable sealing up the propane hose hole. Its supposed to be a "sealed" box.

I agree.

Also, are you guys *sure* I only need the outtake hole and not the intake?

What would happen if you make a hole in the bottom of a sealed bucket of water?  Same thing will happen with propane.  The heavier than air propane will flow out and air will flow in - same hole.  If you want a faster flow rate, make the hole bigger or add a second hole.

-- Spiff

 

[One Awesome Inch]

Pics






http://imgur.com/gallery/i2thIRn
http://imgur.com/gallery/8iLLXsn
http://imgur.com/gallery/vDRpd4c

 

[One Awesome Inch]

Good point. I think I'll make the second hole. Also, since my one and only hole saw is one inch (should I say "one awesome inch"!!!)thats the circumference of all holes I'll be drilling.

As to keeping bugs and mice out, I'm just going to put a few screws in the bottom of the pipes and skip the mesh. The mice wont be able to get past them and I'm not concerned about bugs. They'll be entering a sealed box with no food. Additionally, being 100% urban stealth, I'm parked on pavement 100% of the time, usually nowhere near grassy areas. Critters are less of a concern for me.

 

[Optimistic Paranoid]

. . . I'm not concerned about bugs. They'll be entering a sealed box with no food.

I have heard - but don't know for sure - that wasps are attracted by the smell of propane.  You might want to research that for yourself.  My concern would be that when you need to open the box to change the cylinder, you discover a wasp nest in there. 

Regards
John

 

[highdesertranger]

I know the mud dauber wasps are attracted to propane and Coleman fuel vapors. highdesertranger