Re: Bucket Elevator 'Burp'
First of all what probe are you using? Is it compatible with the MFA-4? What is the target shape for the probe? Is it multi targets in one shaft revolution or 50% on and 50% off in one revolution. Or is the prob detecting the buckets themselves? If the latter does the belt mistrack during a full revolution and exceed the sensing limit of the sensor? By you saying "it sounds different" - this may be the case. Help us help you by giving us as much information as possible. Pictures help tremendously.
If a small slow down in motion is not critical and you are only concerned if the unit has stopped running. Put a timer circuit in the logic set for a few seconds to allow the "burp" to by-pass. If the problem is still there after the timer runs out then let it shut it down. Make sure that you are using a good quality shielded cable for the signal to the controller. I had a situation once where a 2 way radio would trip an alarm just from the frequency of the radio near by. It came down to poor quality signal cable.
Make sure the sensor cable polarity is correct. Having it backwards can cause the contacts to remain open. I couldn't find a manual for the MFA-4 but I did find one for the MFA-4P which says the LED's under normal operation are LED 1 - pulsing, LED 2 - steady on and relay closed. If the relay itself is defective the LED's would be the same and the relay would be open.
The MFA manual should have a trouble shooting guide to show you how the test the circuitry of the mother board.
Might not hurt to bring in a rep from Seimens/Milltronics to check out the components and the circuitry. ■
Gary Blenkhorn
President - Bulk Handlng Technology Inc.
Email: garyblenkhorn@gmail.com
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Offering Conveyor Design Services, Conveyor Transfer Design Services and SolidWorks Design Services for equipment layouts.
Speed Variation On Bucket Elevator - Encode-Transducer R??
elunltd:
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I can provide details on these transducers if you wish.
It is polite to identify yourself when posting question. ■
Re: Bucket Elevator 'Burp'
Originally Posted by Gary Blenkhorn
If a small slow down in motion is not critical and you are only concerned if the unit has stopped running. Put a timer circuit in the logic set for a few seconds to allow the "burp" to by-pass. If the problem is still there after the timer runs out then let it shut it down. Make sure that you are using a good quality shielded cable for the signal to the controller. I had a situation once where a 2 way radio would trip an alarm just from the frequency of the radio near by. It came down to poor quality signal cable.
Make sure the sensor cable polarity is correct. Having it backwards can cause the contacts to remain open. I couldn't find a manual for the MFA-4 but I did find one for the MFA-4P which says the LED's under normal operation are LED 1 - pulsing, LED 2 - steady on and relay closed. If the relay itself is defective the LED's would be the same and the relay would be open.
The MFA manual should have a trouble shooting guide to show you how the test the circuitry of the mother board.
Might not hurt to bring in a rep from Seimens/Milltronics to check out the components and the circuitry.
Thanks for the reply, I apologize for the delay in updating this post.
The new sensor is a 1P7MH71460 -0EA item number 7MH71460EA. The board is a Milltronics MFA 4. I have used the documentation from the MFA 4P to test the unit, this must be a later revision as the board is different and does not include a switch for overspeed/underspeed for example, and is not contained in a case of any kind-just bolted to the wall of the electrical cabinet. When this unit works, the 1 led beats regularly with the sensor, but the other LED that indicates the relay changing state, is out. Also the AC power light on an associated overcurrent relay is not on. When the elevator 'burps', the 2nd LED comes on, the power indicator on the AC current relay comes on as well, for a short time then it goes out again, and the elevator sounds perfectly ok again. The board contacts that are hooked up are the normally closed while the diagram shows normally open contacts. The second disbled MFA for the auger that has been disconnected, has it's disconnected output wires tied together.I have tested both boards on my bench, and seems like it should operate with the second LED on all the time as well, as the 1st led pulsing. I'm puzzled as to the overcurrent relay not getting power, unless this condition happens. It is a normally closed OC relay part number 809S-AB010A1. This does not seem to related to a once a cycle thing as it may happen after only 15 seconds and at very odd intervals, but also always happens when the unit is started. The sensor is detecting the back of the metal buckets, or possible the absense of metal at the back of the buckets. I am going to try a shielded cable grounded only at the cabinet end, as the docs show it should be wired.
I have also recently discovered that an engineer has been called in, because the entire silo may not be plumb, the buckets are crashing into the wall away from the sensor. Of course this may be related too. Thanks for the replies, the unit is out of town, and I will be on site next week again.
Mike ■
Bucket Elevator 'burp'
Bucket elevator 'burp' (bypassing motion failure board, 'cures it'.)
Well that's how the operator describes it. This is very sporadic and it seems electrical in nature. It usually happens after a few minutes, whether the elevator is loaded with product or not.The motion failure pc board, a Miltronics MFA-4 has an led that lights up, when the elevator momentarily 'sounds different', I have scoped the output of the sensor, and there doesn't seem to be missing pulses from the sensor, but seems to be extra ones when the problem occurs. The sensor has been replaced, which did not help. I have built a small pc board that I can feed 1 hz pulses from into the sensor wires on the elevator and it ran for over a 1 hour test without symptoms. Hooking up the sensor again, caused the trouble to happen again within minutes. It does not seem to be related a 'once in a complete revolution' of the elevator, and always happens, though sporadically.The buckets have been inspected carefully for any foreign matter.
I should add that this bucket elevator has been modified, so that the auger that feeds it has been raised about 30 inches, and the motion failure circuitry has been removed and bypassed for the auger only. I am an electronics tech, but have no experience with bucket elevators. I wonder if anyone has a similar set up, with a Miltronics MFA-4motion failure detector. Specifically I would like to know, how the leds are supposed to operate on this board, when the elevator is in motion, and if the output of this board is connected to the NO contacts as shown in my electrical diagram, or the NC contacts it is hooked up to now? I appreciate any responses, it seems I have ruled everything out now. ■