can I weld plastic HDPE?

[stevewilliams]

Hi experts

I have a connector for an IBC which has lots of hairline cracks. It is made of high density polyethylene and it is the threaded cylinder which houses a valve. I don't seem to be able to buy one my size despite hours of internet searching. I don't really want to chuck a 1000 litre IBC tank just because of a broken tap connector. My question is whether these cracks can be repaired? Obviously when full the tank is exerting a tonne of pressure so the seal would have to withstand this. Would heating cause the plastic to flow and fill the cracks or would it just make it brittle?

I've also tried to work out whether I could seal the existing threaded hole and make a smaller one to take a new tap but there's no way of accessing the inside of the tank to thread a nut.

Many thanks

Steve

 

[Jackrae]

Google "welding HDPE' turned up 437,000 hits in 0.66 seconds
This video gives you a good lead
https://www.youtube.com/watch?v=HvV9a3lEe2g

If the IBC has a top filling point then a bit of imagination and dexterity should allow you to fix a nut to a length of fencing wire so's you can position it for picking up a threaded spigot.

 

[cjard]

Last time I bought an IBC it was 25 quid, and for that kind of money I'm not sure I'd spend more than half an hour dicking with it

It's not quite a tonne of pressure because the pressure acts equally in all directions and as a percentage area your tap only experiences a small amount of it. It's the height difference that realises the pressure and it's only a metre, don't worry!

youre probably looking at a couple of psi pressure, hdpe can be welded, but I it worth it?

 

[stevewilliams]

Cheers Jack

The fencing wire idea sounds like it might work for locating but how could you tighten - the nut will just revolve?

 

[Jackrae]

With all due respects, look for solutions not problems. Rotate spigot whilst pulling nut against tank inner wall. or jam nut with a length of wood with a suitably shaped fork end into which fits nut.

Or forget about it and do as cjard states and replace IBC it.

Cracks can spread and unless your welding is full penetration or thick fillet then there's little chance it'll hold up

Water pressure is 1PSI for every 2.4 feet of depth so say your IBC is 3.3 feet deep (1 metre) then bottom pressure is 3.3/2.4 = say 1.5 psi. For 1" spigot, the force is 1.5lbs for 2" spigot the force is 6lbs (increases as the square of diameter)