Catagory: Equipment Tips and Tricks, NCAT Ignition Furnace

Your NCAT Basket Could Be Causing Your Long Burn Times

By: Ryan Olson

Many of you might remember when the square-designed NCAT baskets were the only baskets available. This was before the angled cornered baskets became the standard thanks to some clever marketing and adoption of the asphalt industry. 

Well, in true Gordon Technical fashion, we have revisited the original design, and are surprised by the results.

NCAT sample Basket showing clamp design
NCAT Basket warp after a month of use

Warping Happens

During a burn, the liquid asphalt (which is combustible) ignites from the high temperature in the chamber. The aggregate, which is typically not combustible (unless you’ve got explody rock), stays behind. 

During a test, the heat energy that’s produced from this combustion causes your basket set to warp.

No basket set, no matter how well it’s made, can maintain its shape completely and the angled corner baskets which come included with the Thermo NCAT accessory kit are no exception. 

When baskets warp inside of the chamber during a burn, they can lose 4 points of contact with the hearth plate. This mixed with the draft of the furnace causes the baskets to wobble.

Why should I care about the Wobble?

The NCAT ignition furnace is designed to stop its test once the internal scale stops changing. This makes sense because once all of the liquid has been burnt off, there won’t be anything left to lose (unless your aggregate is prone to explosions).

If your basket is wobbling, your scale will continue to change. This means that your burn will continue to run until you notice it and stop the test yourself.

This can waste hours if you’re not paying attention. We’ve actually seen this happen a lot over the years.

How does Gordon Technical’s basket work any better?

Instead of trying to work against the warp, we designed our baskets to warp in a way that doesn’t disrupt the test. We chose the square design because we found that warping happens in roughly the same area, every time.

We used this information to create a unique foot design that always keeps four points of contact with the hearth plate no matter how much the basket warps.

Then, we tested the heck out of it to make sure that the results all came out the same. We found that even with uneven heating (which can happen if you have an element out) our baskets still maintain all four points of contact.

What about base samples?

Base samples are notorious for longer burn times due to the sheer amount of material that needs to be tested. Sometimes these burns aren’t completed because some of the liquid ends up in the pan and doesn’t burn off.

Why material ends up in the pan

Despite the fact that temperatures in your NCAT ignition furnace are at 1000°F, it still takes time for the liquid to reach that temperature. During that time, the liquid starts to flow and drip into the lower basket.

If enough liquid starts to flow, the material in the lower basket can’t slow it down enough and it ends up moving on down to the pan.

This happens frequently in base sample burns because there is more material to burn.

Why the pan doesn’t burn off liquid

Even though pans are made of metal, the sides can act as an insulator from the heat of the furnace. If there is enough liquid in the pan only the very outer surface burns off, leaving the rest to sit there and harden.

This can be bad because your NCAT wouldn’t know that there’s material still left to burn and therefore would stop the test prematurely. Any liquid leftover can throw off your results.

GTSSI Triple NCAT Basket for NCAT Ignition Oven

How to fix this so it doesn’t happen

Our triple basket set is designed to solve this problem. Our design elevates each basket to stay in the burn area to maximize the available space.

Because the material is spread out across three baskets, the surface area that can be burned is also increased. This means that burns take less time and there is less of a chance that liquid makes it to the pan.

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