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Old February 23rd, 2021, 06:05 AM   #1
lesmar96
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tough environment tail roll sensors

Good Morning,
I have a customer who would potentially like to install tail roll sensors on their conveyors in their quarries. The plc will monitor the conveyor for movement and will shut down conveyors accordingly if there is any problem.

Any one have a good recommendation for or experience with a prox sensor that will is built for a wet/dusty environment like a quarry?

Just checking around for options. Don't want to end up with something that gives us a lot of trouble. Thanks!
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Old February 23rd, 2021, 08:11 AM   #2
Bob O
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Used these at grain elevators.
https://www.go4b.com/usa/products/sp.../whirligig.asp
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Old February 23rd, 2021, 08:43 AM   #3
Ken Moore
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I find Hall Effect sensors work better in harsh environments.
I have had good results from PPI brand devices.
https://www.ppi-global.com/product/speed-switch/
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Old February 23rd, 2021, 09:10 AM   #4
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I've also used these in a mine/coal plant, no complaints.
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Old February 23rd, 2021, 09:59 AM   #5
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What does it cost ?
We manufacture something similar, just a plastic disc with some steel inserts to trigger a nearby prox. I imagine that it cost less to buy a finished unit rather than manufacturing one by ourselves.
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Old February 23rd, 2021, 10:26 AM   #6
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I don't know the cost. The EC provided them at the time and this was many years ago.
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Old February 23rd, 2021, 10:33 AM   #7
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I know a proximity 120vac that can be mounted on the idler shaft. Problem with that is that a bolt needs to be mounted in center of shaft. Kind of hard to retrofit something like that in existing system. I know you can use a magnetic drill to drill it but it always seems like it comes out where its not completely centered.

http://catalog.jamiesonequipment.com...alog%20JEC.pdf
https://www.jpsdesign.com/Portfolios...peedSwitch.pdf

here is a couple of examples above that could be used off the shelf.
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Old February 23rd, 2021, 03:00 PM   #8
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We use these on our dust collector airlocks.
https://controlconceptsusa.com/dazic/.

Dodge also makes " Smart" bearings that are pre engineered to monitor speed, temperature and vibration.

http://www.tecnicaindustriale.net/do...r_bearings.htm.
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Old February 23rd, 2021, 03:15 PM   #9
Ken Moore
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No drilling required for the PPI
Attached Files
File Type: pdf ppi_028-05_speedswitch.pdf (468.2 KB, 11 views)
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Old February 23rd, 2021, 05:00 PM   #10
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Thanks!
you have suggested a lot of nice options. I have sent some RFQs out.
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Old February 23rd, 2021, 05:08 PM   #11
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I would suggest not to place a sensor on the tail drum.
Tail drums often get adjusted to track belts and are usually the lowest point on the belt, where spillage builds up. You will regret it.
Put a floating caster wheel somewhere in the middle of the belt that has a flag on it and use a standard proxy. It will be much more reliable.
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Old February 23rd, 2021, 05:53 PM   #12
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Just checking lesmar as this was not entirely clear to me from your question. Is your client looking into retrofitting on existing conveyors, or rather installing new conveyors with roll sensors installed?


On new conveyors we typically include something like what JesperMP describes. However this means we then use a slightly modified shaft for these new conveyors if our customer specs the option. Retrofits are not common for us. We use standard inductive sensors, either stainless or plastic as most of our products are used in dusty and corrosive environments. The pulse signal goes to a digital input on a PLC. The logic of counting pulses and raising warnings and alarms is done in the PLC.
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Old February 23rd, 2021, 06:13 PM   #13
lesmar96
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Quote:
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Just checking lesmar as this was not entirely clear to me from your question. Is your client looking into retrofitting on existing conveyors, or rather installing new conveyors with roll sensors installed?


On new conveyors we typically include something like what JesperMP describes. However this means we then use a slightly modified shaft for these new conveyors if our customer specs the option. Retrofits are not common for us. We use standard inductive sensors, either stainless or plastic as most of our products are used in dusty and corrosive environments. The pulse signal goes to a digital input on a PLC. The logic of counting pulses and raising warnings and alarms is done in the PLC.

Thanks for asking. This is a retrofit and not a new install. We are looking into upgrading their controls from a simple start/stop setup to an automated process.
Your description is exactly what I was picturing. Use a prox to watch a key or some other target and use a high speed counter in the PLC and run logic from there.
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Old February 24th, 2021, 02:46 AM   #14
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When counting in the PLC rather than in a dedicated piece of hardware, you are either looking into special high speed inputs, or alternatively you make the hardware such that the pulses become longer.



We do the latter which allows us to use standard PLC inputs. We use plastic or nylon discs (I don't know the exact material) bolted to the conveyor shaft. Half of the circumference of the disc is covered with a stainless steel strip. The sensor detects presence of the strip for about half the rotation time, long enough to not miss a pulse. No ultimate precision but it is good enough for the purpose. Works for us.
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Old February 24th, 2021, 04:40 AM   #15
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Quote:
Originally Posted by Toine View Post
When counting in the PLC rather than in a dedicated piece of hardware, you are either looking into special high speed inputs, or alternatively you make the hardware such that the pulses become longer.

We do the latter which allows us to use standard PLC inputs. We use plastic or nylon discs (I don't know the exact material) bolted to the conveyor shaft. Half of the circumference of the disc is covered with a stainless steel strip. The sensor detects presence of the strip for about half the rotation time, long enough to not miss a pulse. No ultimate precision but it is good enough for the purpose. Works for us.
We have two versions of the disc.
One for fast conveyors with the actuating steel insert in a half-moon - like the one you describe.
Another for slow conveyors with the many steel inserts over the circumference of the disc - similar to the pulser disc on page 7 of this PDF http://catalog.jamiesonequipment.com...alog%20JEC.pdf (from Jim3846's post).
For the relatively simple task of monitoring for a stuck belt, there is no need for special fast PLC inputs.
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