Sealing plastic fuel cans

Colin K

Colin K

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Hello,
I wondered if there is a magic method for sealing plastic 5l plastic cans? Tighten them as much as I like, Fill them so there is no air to expand I cannot get them to seal without a weep.
Next thought is to put a polythene seal between the can and top! I would like to keep a few in the bilges as a reserve we are planning a trip to the Scillies in the Summer so might need to carry as much as poss.

Any ideas? Cheers. Colin.
 
Bit messy but a generous smear of heavy grease on the threads assuming it is diesel in the cans. For petrol vaseline perhaps.

Might be a good treatment for some of the threads on here also !
 
I don't think the cheap 5L ones are designed/intended to seal as well as you are expecting.

I have a couple of 10 litre steel cans... made like the big 20L army jerry cans... I forget where I got them, but they lock down tight on a rubber seal and if you are prepared to jam the locking mechanism down so it needs a smack with a hammer to open it, they will seal petrol and diesel indefinitely. They store quite well in small places.

http://www.charliesdirect.co.uk/pad...can-10-litre?gclid=CL_Y3omj1sUCFbQatAodPQoA5A

paddy-hopkirk-handy-steel-jerry-can-10-litre.jpg
 
RichardS said:
I assume that you are leaving some air gap to allow for heat expansion?

Richard
Click to expand...


Ahhhh now you have me here. I filled them to the brim leaving little or no air gap in the belief that air will expand if it gets warm and put the cap under pressure but liquid will not. However its a long time since I did Physics.

Cheers, Col
 
superheat6k said:
Bit messy but a generous smear of heavy grease on the threads assuming it is diesel in the cans. For petrol vaseline perhaps.

Might be a good treatment for some of the threads on here also !
Click to expand...

Hello, Yes its diesel I asked my insurers and they are happy with cans secured adequately. You only need a weep and of course it stinks.

Cheers, Col.
 
I have two plastic 5 l petrol cans. They dont leak and on a warm day pressure can build up and distend them alarmingly.
 
Diesel will expand with heat like air except that it is not compressable like air. So actually you would be better off with an air gap. Jet aircraft run on jet fuel which is not much different to diesel. (in fact they will run on diesel) Expansion is significant in temp changes from 40 degrees or more on ground to minus 40 at high altitude on long flights.
Fuel gauges are calibrated in pounds or Kg of fuel becuase weight matters but also because weight indicates actual amount of energy in tanks as opposed to volume of fuel.
Just waffling they use a capcitive fuel guage sender which does measure amount of energy becuase the dielectric constant varies with temp.
Anyway back to your fuel in containers. Expansion has to be either by stretching the container or by compressing the air gap. If neither of these then comething has to give. good luck olewill
 
Colin K said:
Hello,
I wondered if there is a magic method for sealing plastic 5l plastic cans? Tighten them as much as I like, Fill them so there is no air to expand I cannot get them to seal without a weep.
Next thought is to put a polythene seal between the can and top! I would like to keep a few in the bilges as a reserve we are planning a trip to the Scillies in the Summer so might need to carry as much as poss.

Any ideas? Cheers. Colin.
Click to expand...

Only fill them to the 5 litre mark and they shouldn't leak, mine don't.
 
if you cut a washer from thin sheet butyl rubber, that seems to be a working solution for me. Any damage, however slight, to the lip of the pouring 'tube' allows air and fuel to in- and e-gress, and the washer seals any surface imperfections between the mating surfaces of the tube and the screwcap.
 
Not all of them do, especially the cheapies often found on forecourts. They rely on the screw cap being made from a softer type of plastic than the body to make the seal. Trouble is that if you really turn those screw caps down hard, they can jump the thread and become loose. Just sayin'. :)
 
William_H said:
Diesel will expand with heat like air except that it is not compressable like air. So actually you would be better off with an air gap. Jet aircraft run on jet fuel which is not much different to diesel. (in fact they will run on diesel) Expansion is significant in temp changes from 40 degrees or more on ground to minus 40 at high altitude on long flights.
Fuel gauges are calibrated in pounds or Kg of fuel becuase weight matters but also because weight indicates actual amount of energy in tanks as opposed to volume of fuel.
Just waffling they use a capcitive fuel guage sender which does measure amount of energy becuase the dielectric constant varies with temp.
Anyway back to your fuel in containers. Expansion has to be either by stretching the container or by compressing the air gap. If neither of these then comething has to give. good luck olewill
Click to expand...

Blimey you are of course right and I appreciate your example. I was getting compression and expansion of liquids mixed up so I will be all the more equipt to advise my daughter with her physics! And so an air gap it is.

Cheers Colin.
 
Check round the lip of the container, sometimes in plastic manufacturing there is a join that can stand a bit proud, if there is sand it down to form a smooth surface for the cap to seal against.
 
pvb said:
Plastic fuel containers usually have an O-ring in the cap to seal it.
Click to expand...

As said not all have and IMHO those that do are ****. I replace or fit a proper O-ring from my local seal supplier and have bot had much of a problem. I have even converted several 10 lit plastic cans with connectors to fit my outboards saves lugging heavy 25lit tanks into my dingys.
 
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