Polytex welding help

[DaveTTC]

Not sure if anyone is familair with the leister twinny t

https://www.leister.com/en/plastic-welding/civil-engineering/products/automatic-welders/twinny-t

We use one at work to weld bunker tarps for covering grain. I have been put in charge of the tarp welding crew. Yesterday I was given instruction how to use the welder. From the outset it lioked as though the instructions were flawed. Its not my industry and I am slow to speak up in some things however this seems to be something to speak up about.

Question

If one tarp is slightly overheated and the ither under heated what is the potential outcome?

Could it cause a bad weld and degradation to the overheated tarp thus making it leak?

The welder has two sets of rollers. One set over the heating iron/blower, tje other on the trailing edge. According to the instructions the two tarps are pinched together either side of the iron. This makes sense on a few levels just looking at the design of the machine. The lead rollers appear to bring the tarps together to provide even pre-heat to both surfaces to be welded. The exit/drive rollers both propel along and press the weld together.

This link takes you to the instruction manual.

https://data2.manualslib.com/pdf4/94/9348/934778-leister/twinny_t.pdf?b68619e9032268e4f3018e9b9bc7c729&take=binary

Work has instructed me to place the lower roller between the tarp and heating iron thus reducing the heat to the lower tarp. In my opinion this would prevent sufficent heat to the bottom tarp. In turn the heat is turned up to make the top tarp melt enough to 'stick' to the bottom tarp. Again my opinion is the tarps are more being 'stuck together' as opposed to welded together.

Could this also lead to a lumpy chunky weld bead instead of a nice even weld bead?

DaveTTC
The Turning Cowboy
Turning Wood Into Art

[Simplicity]

My understanding of welding, be it metal or plastic.
Both parent materials need to be rufflly the same temperature.

For then to fuse together probably (flow)

Probably not much help Dave

Cheers Matt

[DaveTTC]

My understanding of welding, be it metal or plastic.
Both parent materials need to be rufflly the same temperature.

For then to fuse together probably (flow)

Probably not much help Dave

Cheers MattThat was my understanding too.

Have just edited to the top post to reflect the instruction given as oposed to the manufacturers instructions.

DaveTTC
The Turning Cowboy
Turning Wood Into Art

[Simplicity]

That was my understanding too.

Have just edited to the top post to reflect the instruction given as oposed to the manufacturers instructions.

DaveTTC
The Turning Cowboy
Turning Wood Into Art

Not an even temperature.
Yes will lead to a "chunky" un even weld.
The technical term is not chunky.
That looks like excreted bird droppings.
There's even a short version lol

Cheers Matt

[DaveTTC]

I will take pics of the welds tomorrow if I get the oppurtunity

DaveTTC
The Turning Cowboy
Turning Wood Into Art

[NCArcher]

The lower guide roller presses the bottom membrane against the heating pad to pre-heat it before it is plasticised by the hot air being forced into the area where the membranes meet. you will get a crap joint if both membranes aren't pre-heated.
If you have offcuts could you do a couple of test welds to compare the weld quality and show whoever appears to be telling you the wrong thing.

[DaveTTC]

The lower guide roller presses the bottom membrane against the heating pad to pre-heat it before it is plasticised by the hot air being forced into the area where the membranes meet. you will get a crap joint if both membranes aren't pre-heated.
If you have offcuts could you do a couple of test welds to compare the weld quality and show whoever appears to be telling you the wrong thing.Yes I hope to do this sometime soon. I am still inexperinced in the use of it. It is primarily a matter of heat adjustment and speed control. I think a couple of test pieces and I should be able to get it.

Last night I sent a text to the 2IC about my concerns. He did say he will discuss this with me today. I await the outcome.

DaveTTC
The Turning Cowboy
Turning Wood Into Art

[rustynail]

You take me back to the good old days, working in the boiling sun, knocking up tarps to cover ground silos. Both layers of tarp should be between the rollers to obtain a good weld. The method you are describing is used in quick fix situations were the tarps are on a dirty surface and the chance of introducing dirt into the weld by the bottom roller becomes an issue. The weld created by this method can only be considered a temporary tack as the joint created is not anywhere near as strong as a full equal heat joint. Your concerns are justified.

[DaveTTC]

You take me back to the good old days, working in the boiling sun, knocking up tarps to cover ground silos. Both layers of tarp should be between the rollers to obtain a good weld. The method you are describing is used in quick fix situations were the tarps are on a dirty surface and the chance of introducing dirt into the weld by the bottom roller becomes an issue. The weld created by this method can only be considered a temporary tack as the joint created is not anywhere near as strong as a full equal heat joint. Your concerns are justified.Thanks, great to have some feedback from someone in the industry

DaveTTC
The Turning Cowboy
Turning Wood Into Art

[rrich]

I have a wire feed welder but I'm not very good at welding metal. So take what I say with a single grain of salt in your beer.

I am surprised that a heat welding process would be used out in the field. Just thinking about getting electricity to the welding machine.

I would think that a chemical process would be cleaner, easier, cheaper and quicker. Just thinking about how we "weld" PVC pipes and fittings. Remember, take what I say with a single grain of salt in your beer.

[rustynail]

Thanks, great to have some feedback from someone in the industry

DaveTTC
The Turning Cowboy
Turning Wood Into Art
Dave, Not anymore mate, that was a million years ago. If I ever see another grain of wheat or itching bloody barley it will be too soon!

[DaveTTC]

I have a wire feed welder but I'm not very good at welding metal. So take what I say with a single grain of salt in your beer.

I am surprised that a heat welding process would be used out in the field. Just thinking about getting electricity to the welding machine.

I would think that a chemical process would be cleaner, easier, cheaper and quicker. Just thinking about how we "weld" PVC pipes and fittings. Remember, take what I say with a single grain of salt in your beer.We take a genny out with a long lead. Each weld is about 37m long and in a good harvest this site could have 100 welds.

Wow thats a lot of welding when I do maths. 3.7 km

The issue with chemical welding I would imagine is wind. Holding the joint while it bonds. For small areas I like your idea. Would be great for patching mouse holes.

If anyone has advice on appropriate glues/chemicals for such I would love to hear it. One other consideration. It would need to be food safe for patching as there is exposed grain when we patch holes. Also needs to be water tight.

DaveTTC
The Turning Cowboy
Turning Wood Into Art

[DaveTTC]

Dave, Not anymore mate, that was a million years ago. If I ever see another grain of wheat or itching bloody barley it will be too soon!Awww now dont be like that, arent you itching to get back into scope 🤣

DaveTTC
The Turning Cowboy
Turning Wood Into Art

[rustynail]

Awww now dont be like that, arent you itching to get back into scope 藍

DaveTTC
The Turning Cowboy
Turning Wood Into Art
Not even remotely. Off season football training used to be bag humping out of empty silos, up a plank and stack out a semi. Wheat was bad enough. Barley was invented by Satan.
As for glue; I do recall an attempt at introducing an adhesive. It was a total failure at the time. Maybe these days there is something better, but I can't imagine it would be much good on site as the dust would be a major problem. We are talking jumbo size tarps here, not your average Bunnings special. Spray tarps would be the way to go. Like the stuff they use in Europe and America for concreting in inclement weather. The small seeds would probably stick to it (see,I told you grain was a bitch) but it would only be a thin single layer of grain. I don't know how this stuff would go for folding back and forth so it would probably only be suited for smaller dumps with a one off extraction.

[DaveTTC]

I hear you on scope and barley lol.

Spray on sounds good

DaveTTC
The Turning Cowboy
Turning Wood Into Art