Post By moonlight machine
silicone gasket for gas can
I need to make a simple gas can gasket. I have some sheet silicone, no idea where it came from, may even be from bake ware. I understand that silicone is vapor perimiable. how will it work for gasoline. Will it allow the gas to go stale too fast. Other choice I have on hand is cork gasket sheet. No idea how that will work with new improved? fuels.
Yes I know I should buy the right stuff but this a holiday weekend and I just want to make sure the silicone will not disolve.
Use the cork, silicone will probably swell.
Moonlight machine is right--silicone will not be suitable. To determine material compatibility you can consult the many chemical resistance charts which are readily available on the web.
For a holiday weekend, paper - as in cardboard cut from a school-tablet back - will work better and last longer. There can be over a dozen different chemicals in pump gasoline, not all of them friendly to the components of silicon-rubber. Unless you have a stash of the variious sheet-goods and sealants specifically intended for fuel systems, anyway.
Originally Posted by Bill D
Next hint would be that El Cheapo plastic gas cans use plastic directly for containers, spouts, cap, and sealiing disc.
WHICH of the 40 brazillion available plastics?
But the likely suspects include polypropylenes and polyethylenes, including the polyethylene terepthalate (PET) of recyclable food and drink containers.
Multiple possible hazards of gasoline as they are, 'most wiser' to get a 'proper' cap and gasket at first opportunity. They are sold separately, and generally cheaply enough it ain't worth the bother of DIY for the one gasket as goes missing or damaged every fifteen years or so.
In the UK the typical 5 litre petrol or gas can is made wholly of plastic - the thread area has a tapered end section to make a seal in the cap, thus there is no gasket to lose.
This is the sort of thing I mean Halfords | Halfords Green Plastic Petrol Can 5L
Last edited by baldwin; 05-26-2013 at 02:17 AM.
Reason: link added
Inner tube will work just fine as a petrol gasket short term with the uk std unleaded fuel. it swells a bit but does not break down - dissolve.
Geez, guys, they DO have compilations of solvent compatibility. The one here states that normal silicone has poor resistance to gasoline. Fluorosilicone is supposed to be pretty good, but that's probably not what you've got.
If the cork sheet is a cork/buna-N composite, it should work great. Test your cork material: put a little bit of gas in an old jelly jar and submerge a bit of cork material. Cover. Check after a few hours to see if it crumbled or swelled. If not, go for it.
this is for a standard jerry can. It may be a California thing but they no longer carry the standard screw on spouts for gas cans here. This means they no longer carry the simple flat gasket either. A few places left to try after the holiday.
If you're talking about an old military gas can, I tried a silicone gasket years ago. It sealed well enough, but it was too soft, and it couldn't handle the twisting that was part of closing the cap. Gaskets are available on-line from military surplus dealers, but if you buy any, be sure they are still soft. Gaskets get harder as they age, and they won't seal worth a hoot.
Short term might be some cork or fiber gasket material. I've cut similar gaskets using a chunk of plywood chucked up, and then staple the material to the plywood, making sure that the staples are outside the gasket area. Grind a lathe bit into a knife shape, and cut the center out, then cut the outer diameter. Don't try to use an Xacto-knife blade or a utility knife blade - they don't survive for very long.
Military gas cans normally need a tool to tighten - the standard 18" long heavy-duty screwdriver works well.
FYI: In WWII, there was a shortage of tankers (due to German submarines), and the military had a hard time shipping gasoline to Europe. Since the military also needed gas cans, some genius got the idea to ship filled gas cans by liberty ship. The cans never seem to seal 100% - about 98% is about as good as it ever gets. The end result was that they had an entire ship full of 5-gallon cans, with every one of them leaking just a little bit as the ship rolled and tossed. One captain reported that the ship's bilge pumps were always pumping gas along with normal bilge water, and that the "smoking room" was a lifeboat that was towed behind the ship. Also remember that Liberty ships were steam powered. Sounds like an interesting way to make a living....