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View Full Version : Propane / MAPP compatibility?



dixdance
07-31-2008, 10:52 AM
I'm getting one of those adapters that lets you refill small 1 lb propane bottles from a 20lb barbecue tank. Should save me 80% on torch fuel! I've been using my turbo torch to power a small homemade forge to do some blacksmthing, and I'm going thru tanks at a clip.

Anyway, I have a bunch of empty MAPP gas cylinders, and I'm wondering if there is any good reason not to fill those with propane also while I'm at it. I'm assuming there is a small residue of MAPP in them.

I can paint them black and label them to avoid confusion.

Richard

oldtiffie
07-31-2008, 11:26 AM
Hi Richard.

I don't know how it is in the area where you live, but here in OZ, any bottles from which Propane (LPG) is de-canted have a tube from the valve to the bottom of the bottle so that you are drawing off liquid instead of vapour from the top as is the case in normal bottle. I have seen it done by inverting ("up-ending") the "normal" bottle to be decanted from.

I have no idea as to whether LPG should or should not be decanted into MAPP cylinders.

I've used my 20# LPG bottles for heating/forging lately.

Some years ago I gave away a forge that I made many years ago. It was lined in refractory ("fire"/"boiler") brick, had a grate in the bottom and was connected to the "blow" outlet of a domestic vacuum cleaner. The air flow was controlled/regulated with an adjustable by-pass "shutter" valve/plate. It was fueled with forge "coke" (the real stuff) earlier and with BBQ "fuel beads" later on. I could get 2" square steel white hot in it without to much effort or time. Made a fabulous BBQ and "warmer-upperer" for late night booze-ups too!!! And it had to be cheaper than LPG/propane - and we had 100# LPG bottles (bulk prices) then for domestic cooking (we have reticulated natural gas now).

biometrics
07-31-2008, 02:42 PM
It has been many years since I used Mapp gas, but as I recall, they have a different thread on the connection fitting that standard propane containers... I don't think you can refill them with Porpane without making your own adapters... Probably not a good idea.

pressurerelief
07-31-2008, 03:02 PM
Dixdance,

I believe the cylinder you are talking about is a DOT 39. Not advisable or legal to refill those "single use" cylinders. The valve is the cheapest thing made and will leak on you sooner or later. There is no 80% spit valve like on your 20# propane to know when to stop refilling. You would have to refill with a scale to keep it at less than 80% full by volume. It is tempting by I would not do it.

People ask why they sell the fitting if it is illegal. I tell them the fitting is not illegal, just using it is. Kind of like rolling papers.

You can buy a fitting and hose that would go from your current 20# cylinder and plumb straight into your forge. Alot safer, legal, and no hassle of refilling.

I work on problem gas cylinders for a living and would not do it.

P/R

RancherBill
08-01-2008, 12:40 AM
Pressurerelief is right it is not a good idea.

The phrase non-refillable always scares me in a situation like this. They were designed for a specific use and with specified usage life. You are exceeding the design parameters of the product. Propane is very dangerous.

I believe there are adapters with a hose that you can buy probably at a commercial plumbing supply.

oldtiffie
08-01-2008, 02:58 AM
All of my 20# LPG bottles have a "Safety Fuse" that shuts off supply (and needs to be physically re-set) if demand is too high (rarely if ever) or if a hose is broken etc. (more often).

LPG in its free state is dangerous. It is heavier than air and gets everywhere - just lurking and waiting for a source of ignition. The odour/smell put in does not always work if you have a head cold or sinus problems.

If the LPG ignites or explodes, it is surprising what else it will or might take with it in many shops. There are often big amounts of highly flammable/explosive "stuff" in a shop.

If you are using a lot of bottled LPG, why not set up two 100# bottles in manifold outside your shop?

It can be bad enough in a shed/barn etc. with doors opened that is away from the house. It is potentially catastrophic in a shop in a garage attached to the house at ground-level. It may be a disaster waiting to happen in a basement.

PTSideshow
08-01-2008, 07:05 AM
Dixdance,

I believe the cylinder you are talking about is a DOT 39. Not advisable or legal to refill those "single use" cylinders. The valve is the cheapest thing made and will leak on you sooner or later. There is no 80% spit valve like on your 20# propane to know when to stop refilling. You would have to refill with a scale to keep it at less than 80% full by volume. It is tempting by I would not do it.

People ask why they sell the fitting if it is illegal. I tell them the fitting is not illegal, just using it is. Kind of like rolling papers.

You can buy a fitting and hose that would go from your current 20# cylinder and plumb straight into your forge. Alot safer, legal, and no hassle of refilling.

I work on problem gas cylinders for a living and would not do it.

P/R

I have to agree with PR I have the hose he is taking about and use it on the BBQ that uses the small bottles all ways seemed to run out of the last bottle in the middle of the meat:rolleyes:
The local BBQ parts place had the correct hose for around $25.00 Mine has the adapter buit into the hose.
I have one of those refill fittings and having tried to use it twice it is a pain in the Seat cushion first off. Secondly it will not fill the tank full. And it seems that each time I refilled the small tank less would go in.
Plus it is dependent on the temp of the bottles etc. And the instructions tank about weighing, a water bath for one or both tanks. Just not worth it with the adapter hose, I spent more of my time getting it to work than 3 of the hoses would have cost me.:D

dixdance
08-01-2008, 12:13 PM
Well... not only is it unsafe, but it doesn't even work well!!!

Thanks for the information everyone, sounds like the hose is the only way to go. Glad I asked on this forum, could have been ugly.

Richard

pressurerelief
08-02-2008, 02:21 PM
OldTiffie,

The device you are talking about is an excess flow check valve. It is basically a slug in the valve that if to much propane starts to go through the passage it takes the slug along and seals off the end of the passage. The other benefit is if you tip over the cylinder, the slug seats and shuts everything down to a trickle via gravity. It you would introduce liquid propane into a system designed for vapor you would have a big fire. We burnt down half a city block last winter due to just this. A worker backed into a cylinder without this protective device and the rest is now ash. Nore Roberts had to start rebuilding her hotel from the ground up.

http://www.wusa9.com/news/health/story.aspx?storyid=68849

P/R