3 phase sewage scraper bridge with 24VAC control issues

In summary, somebody has been playing with the wiring and it's causing the chattering issue on the sewage scraper bridge.
  • #1
NicolasW
1
0
Guys,

I'm having a lot of issues where I work with a sewage scraper bridge chattering it's drive contactors when being called to run, the coils for
the contactors are switched on their neutrals from an Allen Bradley logix processor. The control circuit is 24v AC. I've spent a few hours on this over the past week with little success. I appear to be getting large volt drops on to the coils of the contactors, down to 13v in places. I've replaced both the control transformer and the Allen Bradley processor which has made no difference.

It's worthy of note that a new guy has started and installed polarity sensitive beacons on top of the control panels to signal when the bridge is running. Depending on where he's tapped into the supply, could this cause the issue, I've not been back to look yet to see if this is the problem, could it be likely?

Here are some drawings

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A878A54B-E107-40CB-B7DA-82B6E2B88197_zpstck8h8q4.jpg


7A2C2628-1465-44B0-81BF-EF0D91C2DF52_zpswinebook.jpg


1427EADF-F371-4295-B8AF-B4F382752A29_zpsndhnrbjr.jpg


B0C44D75-210F-463E-BCF8-03149BC631BC_zpsihkl4zhs.jpg


Hoping you guys can give me some pointers.

Thanks
Nick
 
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  • #2
What do you mean by "polarity sensitive" beacons? If the controls are ac then there is no polarity.
Could the use of dc(?) beacons be causing an issue? quite possibly. I would disconnect the beacons and see.
If so get 24vac beacons.

Do the contactors for the scraper lift , and lower chatter only or are there more that chatter?
 
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  • #3
If there are voltage drops on the coils work back from there to the power source to see where the drop is introduced.

Bad cable joint?
Wire gauge too small?
24v supply overloaded?

PS: Also check for problems with any common return (0V or earth). It might not be the 24V "coming down" but the return/earth "coming up".
 
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  • #4
NicolasW said:
Depending on where he's tapped into the supply, could this cause the issue, I've not been back to look yet to see if this is the problem, could it be likely?

Analytical Troubleshooting training courses teach :
'if it used to work and now it doesn't work, something has changed.
Things can change by normal wear and tear,
or they can be changed by somebody tinkering around.
If somebody has been tinkering , that's the first place to look. '

What wires got moved?
 
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  • #5
jim hardy said:
...they(things) can be changed by somebody tinkering around.
If somebody has been tinkering , that's the first place to look. '

What wires got moved?
Tinkering has brought on several tears over the years, for me. Very good point.
 
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1. What is a 3 phase sewage scraper bridge with 24VAC control?

A 3 phase sewage scraper bridge with 24VAC control is a type of bridge used in sewage treatment plants to remove solid waste from the water. It consists of a rotating mechanism with scrapers that move along the bottom of the treatment tank, pushing the waste towards a collection point.

2. How does the 24VAC control work in this system?

The 24VAC control in this system is used to power the motor that drives the rotating mechanism. It receives signals from sensors that detect the level of waste in the tank and adjusts the speed of the motor accordingly. This ensures that the scrapers move at the appropriate speed to effectively remove waste from the water.

3. What are some common issues with the 24VAC control in a 3 phase sewage scraper bridge?

Some common issues with the 24VAC control in a 3 phase sewage scraper bridge include power supply failure, sensor malfunctions, and motor overheating. These issues can result in the bridge not functioning properly and can lead to clogging or overflowing of the treatment tank.

4. How can these control issues be resolved?

To resolve control issues in a 3 phase sewage scraper bridge, it is important to regularly check the power supply and sensors for any faults. If any issues are found, they should be addressed immediately. Additionally, proper maintenance of the motor is essential to prevent overheating. It is also recommended to have a backup power supply in case of power failures.

5. What are the benefits of using a 3 phase sewage scraper bridge with 24VAC control?

Using a 3 phase sewage scraper bridge with 24VAC control can greatly improve the efficiency of a sewage treatment plant. It ensures that solid waste is continuously removed from the water, preventing clogging and overflow. It also allows for automatic control of the scrapers, reducing the need for manual labor. Overall, this system helps to maintain a clean and functional treatment plant, promoting a healthier environment.

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