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Old February 13th, 2020, 11:23 AM   #1
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JankyPLC is offline
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All Weather Sensing?

Heres the situation, CDLR conveyor feeding pallets of product through the building wall, last 12 feet are exposed to the weather (midwest) so the pallets can be picked by forklift drivers outside to be taken wherever. System needs to be able to run 24/7/365.

The problem: We need to sense the product on the conveyor to know when and when not to send more pallets. PEs work fine in nice weather, but we've had nothing but trouble finding a way around snow. Between roller is preferable to eliminate the risk of forklift damage.

We use Sick 1063129 indoors with great success. Outdoors despite the rating, we have condensation issues under the lense, and snow buildup on the lense, even with hoods and blowoffs, and rollers prevents proper sensing.

Above the rollers is an option but then it becomes a game of how to protect from forklift drivers, and snow on sensor faces can still be an issue. Does anyone have experience or ideas on how to combat?
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Old February 13th, 2020, 12:29 PM   #2
Kip Williams
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Load cell???

Maybe consider adding a load cell under the conveyor legs.
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Old February 13th, 2020, 12:41 PM   #3
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I have used Sick heated photo-eyes and heated reflectors in Freezer environments that were at -10F. We had condensation issues when when mounted hear a freezer door that went from the -10F to 28F temperature. The heated components helped a lot. Not sure anything would help if you got a large amount of snowfall.
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Old February 13th, 2020, 04:26 PM   #4
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Capacitive proximity perhaps? In between the rollers looking up - they'd need to be pretty flush so they were close enough to detect wooden/plastic pallets, but you'd have no issues with condensation etc.

Not sure if they'd be able to distinguish between a wooden pallet and a large dump of snow, but then again that's probably no worse off than any other sensor. If you have hoods/blowoffs in place already, that may get you by.

Otherwise you could look at a small form factor ultrasonic sensor. I had a client with a similarly challenging application - detecting trains in a coal loading facility. Everything was absolutely caked in coal dust within 5 minutes of operation, and the trains were a fair distance from the sensor mounting location, and they were all different sizes and shapes so the distance from sensor to train varied quite a bit. In the end he found an 18mm barrel-type ultrasonic switch, and it worked like a charm.
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Old February 13th, 2020, 05:02 PM   #5
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Originally Posted by Kip Williams View Post
Maybe consider adding a load cell under the conveyor legs.
This would be much more bullet proof. Costly but once set up, should be solid. I worked in a food plant that had Emery Winslow Hytronic (hydraulic) load cells mounted on some massive mixers and grinders and they were bullet proof. The electronics were well protected in a separate enclosure where the four corners were summed and scaled and sent off the a display/transmitter in a separate room away from the washdown environment. Once in a great while there might be a leak and the techs would have to purge out air and refill the lines. I was amazed that we could weigh a 10000 pound batch of meat in a 50000 pound machine and get within 10 pounds pretty consistently.
You can choose a ready guide in some celestial voice. If you choose not to decide you still have made a choice.
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Old February 13th, 2020, 05:40 PM   #6
James Mcquade
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Can you install a canopy over the line and allow the fork trucks to pick up the pallets? have the canopy 2 times the width of the line and conveyor on each side to help block the snow and rain. make it wider if necessary. that's what we did.

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Old February 14th, 2020, 01:26 AM   #7
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I have seen CDLR with one of the entrance rollers removed from the chain drive and then spring loaded to sit a little bit higher than the rest of the rollers. Then once a load is placed on it, it pushes down and an inductive sensor is used to detect the roller shaft.
Something like the SICK IQG inductive range will work well in very harsh conditions
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Old February 14th, 2020, 01:46 AM   #8

ValeoBill is offline
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What kind of control system? A PLC could use a shift register to track the part. A pulser on a chain driven sprocket could measure distance travelled. A physical positive stop should be used as a backup in the event of a switch failure.
I've had some luck using ultrasonic switches monitoring parts travelling on a monorail. They work well in heat and dirt environments. I don't know how they would hold up in your environment. If it comes to it, call in sensor manufacturers. They are all too happy to help if it means a significant sale or even just getting their foot in your door.
Keep us posted on how you make out.
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Old February 18th, 2020, 09:19 PM   #9
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rankhornjp is offline
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Does it have to be non-contact?
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Old February 19th, 2020, 01:20 AM   #10
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I have tackled this a few times using ultrasound sensors, get some with a long range and place them in a 45 degree angle with a cover 200 mm above them, so you shoot clear of the cover and no snow will build up on them.
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Old February 19th, 2020, 08:17 AM   #11
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What about a Laser beam sensor (break Beam) to detect that the truck is in at the loading point. You get single point ones that detect a reflector. We use it to detect tank position to advise the forklift to stop using a traffic light system.

IFM do

Guess you could also at angle so pallet in position breaks beam

Last edited by mad4x4; February 19th, 2020 at 08:20 AM.
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