Sensor for hot environment

Hey guys,

Not strictly PLC related, but I could use some advise. I am needing to sense a donut shaped metal object that is around 550F, and more specifically, trying to make sure that the hole is not too big.

The "donut" itself is around a foot in diameter. The two possible hole sizes I could see, would be approx 2 inches in diameter different.

If everything were cool, I could use a photoelectric sensor and sense the outer edge of the small hole. Then if a "donut" with a big hole were present, the photoeye wouldn't see it and I could stop the process.

However the temperate is killing me. I could use a limit switch with a long arm and back the switch away, but it won't be as precise and I can see people bending arms and what not, defeating the purpose.

Saw in a catalog some fiber optic sensors that I could potentially use, where the cable can withstand high temps. But have no experience with them, so can't attest to their reliability.

Anyone have any other suggestions on how to differentiate between the two "donuts", or have experience with sensors in HOT environments?

mutabi,

you haven't described the machine so I will offer some ideas.

1. vision system - I use Cognex
2. analog sensor mounted to a cylinder that you move up / down
with a centering point.

others may better solutions.

regards,
james

Thought about a vision system, but without having used one before, I can't attest to their durability in a hot dirty environment. The machine itself is a 3000 ton Press. The "donuts" stand up on their edge, and thats the only view I get of them. They don't lay flat. There is a lot of vibration with the machine, which I would think could cause issues with the vision system. Again, I don't have experience with them.

Thought about a cylinder, but was hoping for something simpler(would be a nightmare to try to install one with the setup we have). I'm all out of simple ideas that would be reliable in that environment.

When I worked on the Steel mill we used these.

http://www.bannerengineering.com/en-US/products/sub/50#literature


http://info.bannerengineering.com/xpedio/groups/public/documents/literature/03416.pdf

They are called Banner maxi-beam. You can chose an option with Glass and fiber optic heads. This enables you to put the power unit a safe distance away and the photo beam/ fiber is encased in a small flexible stainless steel conduit. We had the fiber in at least 700 degree F temperatures

call keyence

Can you get a laser beam to hit it, they can shoot pretty far. Keyence will come out with a sample and try it for you.

Thanks for the last two suggestions. Definitely possibilities I will be looking into!