11 replies to this topic

[cooperman435]

Has anyone had any experience and preferably luck with gluing end plugs into HDPE tube?

Curently Im having to make my endplugs loose and quite tapered then puting them in wide end first, applying copius amounts of hot glue to the tubes sides and blowtorching it to melt the two together. I then turn the tube over onto a peice of paper and force the plug down to the end of the tube to push it into the glue and seal all round it.

I tried screwing and nailing them in place but no luck as loads popped out on lift. None of the hot glued ones have ever had a problem but its so time consuming especially for the larger ones.

Edited by cooperman435, 17 November 2007 - 10:15 PM.

[ProfHawking]

i think most have wooden plugs, and they have nails round the edges going through the tube walls into the plug.
What material are your plugs made from? Not sure there are too many very effective glues for wood/plastic joints.

[cooperman435]

i think most have wooden plugs, and they have nails round the edges going through the tube walls into the plug.
What material are your plugs made from? Not sure there are too many very effective glues for wood/plastic joints.

They are 3.5" long wooden plugs made from 3 peices of 1" plywood. I tried making them a very tight fit to help but they still pop out and shear the screws (12 of them) in half!

[pyrotrev]

They are 3.5" long wooden plugs made from 3 peices of 1" plywood. I tried making them a very tight fit to help but they still pop out and shear the screws (12 of them) in half!

Sorry to disappoint you Phill, but polyethylene is a bugger to glue. If you do some careful surface preparation (lots of cleaning then rough it up with an electric discharge there's a few evil glues that do a reasonable job I believe, but whether they're up to firing cylindrical shells I don't know . In commercial installations all the high pressure systems in PE that I've seen use fusion welding, normally with a coupler that has a coil of resistance wire in it, that melts both the coupler and the pipes to be joined. I imagine if you were ingenious you might be able to place a copper ring around the outside of your plugs and induce some current in it from a semi-dismantled large transformer for the same effect. Or maybe it's possible to flame weld a PE disc into the bottom?
Or for a low tech solution, I found that coach bolts into a wooden plug worked OK in my 8's .... at least for the relatively few firings they get.

Edited by pyrotrev, 18 November 2007 - 11:14 AM.

[Mortartube]

Use solid wooden plugs, the force of the lift is probably damaging the veneers of the ply and causing the problem. Turned pine plugs of the same dimensions should be fine, Chamfer the edge that's going into the tube and hit the plug square on with a sledgehammer driving it in. It is a knack and you may need a bit of practice to hit the plug squarely. Then just drill the outside of the tube and a little into the plug, and put in screws. It should last for years. I sometimes smeared a little pva on the plug to seal any deformations in the tube but otherwise this method worked fine for me for years.

If they just popped out, they were probably a little undersize. The plug should be a tight fit and the plug should do a lot of the holding itself in the tube.

Edited by Mortartube, 18 November 2007 - 12:49 AM.

[Bonny]

You could also try ramming a layer of clay maybe 1" thick or something over top of the wood plug. Another possible solution might be drilling holes and putting small bolts all the way through...maybe 90 degrees apart and at different levels.

[Arthur Brown]

HDPE must be one of the more difficult things to glue!

Try cutting a short length say an inch off a tube, cutting a small amount out of the ring and making the slit ring go inside the remaining tube. get some wire and try a fusion weld of the ring to the tube then drop the plug onto the ring.

Look at how the gas/water utility suppliers do their underground pipe joints. Try to get some ready made short ends with covers welded on!

[cooperman435]

well im gonna try some tight wooden plugs with 2 part epoxy then. Ill rough up the inside of the tube a lot first and make the plug very tight.

I was hoping to find some hdpe block that I could make a plug from and wrap some nichrome wire round it before putting it into the tube and applying current to melt the two together. If anyone has any suggestions od where to find such a peice of plastic then please let yourself be known.

[Arthur Brown]

Cut an inch off the tube and make it into an inside circlip then wrap in wire and fuse it, then give it a cooling time.

Added: search the www.HSShire.com site for electrofusion and read the PDF that goes with the generator set.

Edited by Arthur Brown, 19 November 2007 - 10:12 PM.

[Mortartube]

Upon re-reading your post I realise that you said they were tapered. That could be part of the problem. Parralel sided pine plugs with just the corner of the leading edge chamfered and applied as I said will work every time. You are simply making more work and cost for yourself with all the electric welding ideas etc, with no guarantee of success. The method I have outlined is proven to work and some of my old HDPE tubes are still in use by another comapany between 10 and 15 years later.

Make the plug tight.

For the chamfer on the top you just need to turn off the harsh corner on the leading edge so the width of the band you have created is about 5mm wide

Edited by Mortartube, 20 November 2007 - 01:19 AM.

[cooperman435]

The tapered plugs used the hot glue method and they are to date the only reliable way of plugging the end Ive tried.

The screwed and glued ones were parallel and tight to the tubes as you say but maybe not tight enough or a good enough glue. Lets hope it works this time.

Cheers all

[aquarius]

My 2 cents (or 1 p) on this is that your endplugs are tapered. If you insert them "correctly", only a part of the plug will be in close contact with the inside wall of your mortar tube. If you use a thightfitting round plug (as in not tapered), there will be more friction and thus more resistance against the wall og the tube. Using one solid plug opposed to three single will be an advantage anyhow, if you are not into crosslaminating the plugs. Imagine three layers of plugs. If the first plug that goes into the tube is only slightly bigger than the next, the tube will expand to pass the plug. Neg next, smaller plug will not have the same grip. therefore, use a single round plug without taper and anchor the plug in yuor tube with (wooden) nails.