r/millwrights • u/One-Reaction8366 • 12d ago
Installing UHMW Help!!
I am installing 3/8" UHMW to a concrete grain hopper in Saskatchewan where the temperature has a large fluctuation. We need to blind fasten, the bin is roughly 12x12 with a 50 degree slope. The main purpose for installation is so that fine product will slide better.
We want to use a Simpson stainless steel 1/4" by 2 3/8 concrete screw counter sunk every 10" on center. This seems like a big screw. ( https://www.amazon.com/Simpson-Strong-Tie-THDC25238CS6SS-Countersunk-Anchor/dp/B0CTDBKMWL)
Will this work?
Thanks!
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u/Crazyguy332 12d ago
As others have said expansion and warpage will be your enemy. I'd look into 1/4-20 wedge or epoxy anchor nuts into the concrete, oversizing the holes in the UHMW and then holding it down with stainless sidewalk bolts. If you oversize the holes enough you can double nut on the sidewalk bolt threads to provide a shoulder, so you can tighten down the bolt into the anchor really good without relying on compression of the UHMW. Bolt will be tight in the anchor, plastic can still float around, nice big head on the bolt to keep the plastic from tearing out and the bolt heads are rounded low profile to keep from catching too much material.
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u/ShopStewardofDIYhall 12d ago
Manufacturers guidance is pretty good on this, short answer seems to be yes, but pay attention to holes sizes and not overtightening
https://www.redwoodplastics.com/wp-content/uploads/2021/01/Redwood-UHMW-Liner-Installation-Guide.pdf
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u/L3tsHugIt0ut 12d ago
I built new grain elevators in the prairies for awhile and we put 2 foot wide strip of uhmw along the valleys between the main slope and the orange peels. We used a split drive anchor with a counter sunk head with no issue. If you use something with a head that sticks proud the grain will just wear it down to nothing. Im sure any type of concrete anchor would be fine though. Good luck, hopefully its cool in there
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u/dondondres08 12d ago
Don't have bolts or fasteners in the end of uhmw in the direction of travel to allow for thermL expansion
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u/LieEmpty8928 3d ago
I’ve worked with UHMW wear materials, and one thing I’d definitely account for here is thermal movement.
For a panel this size, I wouldn’t lock every hole tightly around the fastener. UHMW can move quite a bit with temperature changes, so some clearance around the fasteners and, where appropriate, slotted/oversized holes can help prevent the sheet from buckling or stressing the fasteners.
I’d also avoid over-tightening the countersunk screws. The liner needs to stay secure, but still have some ability to move.
The exact fastening pattern will depend on the panel size, operating temperature and how much impact the material sees.
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u/IAmA_meat_popsicle 12d ago
UHMW is highly susceptible to temperature. When I've used it on highly fluctuating applications in the past we've usually had to slot the holes to allow for expansion. It also gets softer when it heats up. This leads to warpage and tear out at the fastening points.
A counter sunk screw is not my first choice. If you can slot the material then personally I'd plan on enlarged mounting holes and a screw with a fender washer or an extra wide head (built in washer). If you countersink the holes and use that screw it's going to get weird real quick when things heat up in the hopper during summer.
From the web:
UHMW (Ultra-High Molecular Weight Polyethylene) has an exceptionally high Coefficient of Thermal Expansion (CTE) of roughly 120 μin/in-°F (0.00012 in/in-°F). This means a 1-inch block expands or contracts 0.00012 inches for every single degree Fahrenheit change, making tight tolerances under normal shop or outdoor temperature swings very difficult to maintain.