S800IO - AO810 signal out intermittent

Hi,

Currently, my control panel is using AO810 with TB810 for controlling our field instrument which supports 4-20mA signal for opening & closing temperature control valve(TCV).

However, recently we found out that when we are opening/closing the TCV from faceplate, the signal out from A0810 is intermittent to the device thus causing the opening/closing will not be smooth, for example, it will open awhile then pause then again continue to open then again pause repeatedly until it reaches the setpoint. This applies the same for closing.

We have tried to test on different AO channel on same AO unit and it is still the same. We have changed the new valve and also new AO810 unit, the result is the same.

Can anyone advise/share what will be the root cause and solution for this matter?


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jeevan84   

asked 6 months ago
Closed



Best Answer

1

Hello,

I hope this is the problem with only one perticular AO810 module connected with some TCVs (control valves)? Does this problem is a recent finding? I mean it was working before and not it is giving problem?

As you have already changed the valve (positioner??) and AO810 module, still the problem persists! Hence i think there wouldn't be any problem with AO810 and Valve individually!!

I suggest you to check the AO810 output with mutlimeter or another recorder by disconnecting valve. And check the behavior of the 4-20mA output. If this seems to be ok, then test the valve by feeding 4-20mA from mA source from the marshalling termianls. This is helpful to check any problem (eletromagnetic interference) with cable from marshalling to valve.

If the AO810 module output when recorded by disconneting valve is not ok, then another suspected component would be TU810 base. This might be faulty??

If the valve doesn't operates smoothly when operetd by feeding 4-20mA from a source

(feeded from marshalling terminals), then feed the 4-20mA signal to the valve by connecting directly on valve positioner.

If the valve operates smoothly by feeding 4-20mA signale directly on positioner then cable would be problem (EMI) else the valve itself.

If both AO810 and valve are working fine in isolation then obiviously the combination would be problematic. But this case is very rare.

In such case you may install some resistor (resistance) in parallel to the signal wire. Please share the positioner model number too in case of above.

Hope this helps you.

Kumaraswamy.B   

answered 6 months ago


 


By jeevan84 on 11/16/2017 | Like (0) | Report

Hi Kuma,

Thanks for your advise. We have done checking at our side but manually inject mA to the valve from our terminal block before AO810 and the mA injection is able to drive the TCV to our specific opening and closing position smoothly.

May i know what can goes wrong with TU810, as I understand this MTU do not have any active component or electronic, and it is only serve for wiring connection purpose to our AO810. We have checked with our ABB partner, they have suggested to reset the power for the whole cluster that contain these AO810 and we are waiting to make it happen when green light is approved from our manager as the instrument is serving to our end user so it is just a bit complicated.


By jeevan84 on 11/16/2017 | Like (0) | Report

Let me get back to you about the positioner model once I receive from my technician.


By Kumaraswamy.B on 11/17/2017 | Like (0) | Report

Hello,

You are right, TU810 is a passive component and it does not contain any active components.

However the electrical modulebus connections (the male and female connections on left and right side of the TU810) are protected from EM interference. If this protection fails due to some reason it could malfunction.

I hope you might have already tried this AO810 module on other TU810? is this module working with other TU810?

You can try this too before concluding the problem with TU810. I have attached the TU810 circuit for your reference as new answer to this.

You please try the advise given by local ABB partner too.

Please update me too if you find some other is the problem.


By jeevan84 on 11/17/2017 | Like (0) | Report

Hi Kuma,

Noted with thanks. Will keep update you for our finding and testing.


Add New Comment


Answers

0

It is unlikly that a hardware fault in the AO810 will cause this type of behavior. The unit either gives a current output (ie the vale is open) or it doesnt (ie the valve slams shut)

You could make the valve behave like this if you programmed it specifically ( or just really badly), but ...

It is **MUCH** more likely that the valve actuator is packed too tightly and its sticking. This is a very common behavior - called "stiction"

Rob Lyon   

answered 6 months ago


 


By jeevan84 on 11/15/2017 | Like (0) | Report

Hi Rob,

I would agree with you if this happen only on one valve. In fact, all the valves(6nos) that connect to this AO unit are facing the same behaviour.


By Rob Lyon on 11/15/2017 | Like (0) | Report

OK. Have you connected a multimeter with recorder to the Output channel to check the mA readings ?


By jeevan84 on 11/15/2017 | Like (0) | Report

Hi Rob,

According to my technician, they said when operator is giving 25% open, they measure with multimeter, the reading start from 4.01mA, slowly increase like 4.3, 4.5, then 5.2,5.6, 6.4... then reach 8mA. Based on their past experience, if the 25% output, once measure, the reading will go from 4mA to 8mA straight away, not like this case.


By Rob Lyon on 11/16/2017 | Like (0) | Report

Probably there's a rate of change limit on the TCV somewhere. You'll need to check the program.


By kstoilov on 11/16/2017 | Like (0) | Report

Like advice - try to force from Online the AO channel - start from 0% and then write 25% to it's value. You should measure immediate change from 4 to 8mA at the output. If that is the case, you have some ramp limit in your software. Check the way of the signal in software - how the output variable is formed in the logic


By kstoilov on 11/16/2017 | Like (0) | Report

I don't think the problem is in hardware of AO810 or TU810 if the value is changing, even with a ramp


By kstoilov on 11/16/2017 | Like (0) | Report

Have you look in the detailed faceplate or some other settings on HMI for this valve or regulator? May be there is a setting for this ramp or speed of change or something else, which operators changed?


By Rob Lyon on 11/16/2017 | Like (0) | Report

And I think it sounds like you've got instrument techs who have a habit of packing the valve stem too hard !


By jeevan84 on 11/16/2017 | Like (0) | Report

Hi kstoilov,

Thanks for your advise. However, I could not be agreed with your saying as there is ramping setting as we only manually send AO signal direct to the TCV, for let say 25% opening with 8mA and it works before, and till recently it give us issue.


By jeevan84 on 11/16/2017 | Like (0) | Report

Hi Rob,

Thanks for your advise. However, we have used the same TCV in our plant at other section with the same type of AO810, again i couldn't agree with your saying too about the valve stem too hard


By jeevan84 on 11/16/2017 | Like (0) | Report

Hi kstoilov and Rob,

We have even manually inject 4-20mA to our TCV and it is working fine when opening and closing with mA injector from 8mA, 12mA ,15mA and 20mA.


By kstoilov on 11/17/2017 | Like (0) | Report

Did you tried to force the output channel from Control Builder as advised above? In case you set it from 0 to 25%, the output current should go from 4 to 8 mA without delay or ramp. This will say if there is some problem in AO or TU


By jeevan84 on 11/19/2017 | Like (0) | Report

Hi Kstoilov,

Yes, indeed we have tried to force the output channel from control builder. Also experience the same thing, the output current doesn't go from 4 t0 8mA without delay or ramp.


Add New Comment


1

Hello,

I hope this is the problem with only one perticular AO810 module connected with some TCVs (control valves)? Does this problem is a recent finding? I mean it was working before and not it is giving problem?

As you have already changed the valve (positioner??) and AO810 module, still the problem persists! Hence i think there wouldn't be any problem with AO810 and Valve individually!!

I suggest you to check the AO810 output with mutlimeter or another recorder by disconnecting valve. And check the behavior of the 4-20mA output. If this seems to be ok, then test the valve by feeding 4-20mA from mA source from the marshalling termianls. This is helpful to check any problem (eletromagnetic interference) with cable from marshalling to valve.

If the AO810 module output when recorded by disconneting valve is not ok, then another suspected component would be TU810 base. This might be faulty??

If the valve doesn't operates smoothly when operetd by feeding 4-20mA from a source

(feeded from marshalling terminals), then feed the 4-20mA signal to the valve by connecting directly on valve positioner.

If the valve operates smoothly by feeding 4-20mA signale directly on positioner then cable would be problem (EMI) else the valve itself.

If both AO810 and valve are working fine in isolation then obiviously the combination would be problematic. But this case is very rare.

In such case you may install some resistor (resistance) in parallel to the signal wire. Please share the positioner model number too in case of above.

Hope this helps you.

Kumaraswamy.B   

answered 6 months ago


 


By jeevan84 on 11/16/2017 | Like (0) | Report

Hi Kuma,

Thanks for your advise. We have done checking at our side but manually inject mA to the valve from our terminal block before AO810 and the mA injection is able to drive the TCV to our specific opening and closing position smoothly.

May i know what can goes wrong with TU810, as I understand this MTU do not have any active component or electronic, and it is only serve for wiring connection purpose to our AO810. We have checked with our ABB partner, they have suggested to reset the power for the whole cluster that contain these AO810 and we are waiting to make it happen when green light is approved from our manager as the instrument is serving to our end user so it is just a bit complicated.


By jeevan84 on 11/16/2017 | Like (0) | Report

Let me get back to you about the positioner model once I receive from my technician.


By Kumaraswamy.B on 11/17/2017 | Like (0) | Report

Hello,

You are right, TU810 is a passive component and it does not contain any active components.

However the electrical modulebus connections (the male and female connections on left and right side of the TU810) are protected from EM interference. If this protection fails due to some reason it could malfunction.

I hope you might have already tried this AO810 module on other TU810? is this module working with other TU810?

You can try this too before concluding the problem with TU810. I have attached the TU810 circuit for your reference as new answer to this.

You please try the advise given by local ABB partner too.

Please update me too if you find some other is the problem.


By jeevan84 on 11/17/2017 | Like (0) | Report

Hi Kuma,

Noted with thanks. Will keep update you for our finding and testing.


Add New Comment


1

Hello,

If the following components (active and passive) are found to be good, I suspect TU810 would be faulty/malfunctioning as it contains EM protection.

1. Valve/Positioner.

2. Field Cable (Intereference free).

3. AO810.

Could be faulty/malfuntioning??

Source: 3BSE020924-510

Kumaraswamy.B   

answered 6 months ago


 


By jeevan84 on 11/19/2017 | Like (0) | Report

Hi Kuma,

Thanks for your advise. We are currently waiting approval from customer for this kind of activity as we need to shut off the power of that cluster contain these AO810. If found TU issue, we will replace it and turn on power then only can know.


Add New Comment



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