Reliability in Fieldbus system

[Egui]

Is there any real case or study or paper where I can find a comparison between the reliability in classic hardwired I/O system(Junction box-marshalling-Controller) and field bus system.

Many customer do not like to take risk in change their way to do the thing....it´s obvious, it´s better safe than sorry.....

I am not talking about safety loops.(ESD)

In addition is there any cost study (installation safe money, etc)....

thanks in advance

 

[JLSeagull]

BTW the client adds a Balston filter in the instrument air supply to the F-R positioners.

 

[charlesflau]

Thanks very much for all the replies!

The problem we are having is strictly electrical/electronic in nature. When it happens, the positioner will lock up and the only way to fix it is to cycle the power on and off. So far, the problem we have is only with the Valtek 3400IQ and 1400 series positioners. The Fisher Fieldview positioners are fine.

The Valtek specialists are here now troublshooting the problem. I am sure we will get to the root cause(s) eventually.

 

[JLSeagull]

That sounds like a problem that I heard about. I am asking a couple of designers about their previous problem.

 

[charlesflau]

As an update to my previous post, the Valtek specialist explained to us the problem with the Valtek 3400IQ positions was configuration setup. He went through all the positioners to confirm the correct configuration last Wednesday (11/08)and made changes as needed. Since then, we have not had a single positioner failure. We will continue to monitor.

I guess each positioner has a mini "computer" inside and like any computers, it must be programmed correctly to work.

 

[Ashereng]

Yes. That is one of the things with the newer generation of "smart" instruments. You need smart "instrument techs" to configure/calibrate/set-up/ the thingys now.

Glad you solved your problem easily and cheaply. We were not so lucky.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[charlesflau]

Thanks for your comments, Ashereng!

You are correct. We sure do not want to start up the plant and having these positioners failing on us. It would be very expensive shutting down the plant. Plus, the risk of equipment or catalyst damages is high on a plant trip.

 

[controlnovice]

Ashereng nailed it on the head. At least for us.

We will not install Fieldbus unless we are sure the plant personnel is able to maintain it. We installed it once without realizing the tech's learning curve. So now, at that plant, the engineers are troubleshooting instruments. Money not well spent.

______________________________________________________________________________
This is normally the space where people post something insightful.

 

[charlesflau]

Good comments, Controlnovice!

I hate to say it but the company has now made a decision not to install foundation fieldbus in the new plant because of all the problems we experienced.

 

[Fieldbus]

I have to agree with Ashereng - instrument techs need to be brought out of the dark ages and told to leave their flapper nozzles alone.
There is definitely a learning curve with new technology but I am not sure that it is really so steep - if you trust these guys to look after critical instruments now, what difference does it make if it's 4/20mA, HART or FF? Perhaps you need to ask if these guys have an X-Box at home and if they need their kids to set up their video recorder when they go bowling.
The reply from Charlesflau above highlighted that when the correct procedure was followed (dare I say, RTFM), all problems went away. Fieldbus isn't quite plug'n'play yet - the devices have to be told what it is you want them to do over going up & down (or down & up) on command.
One of the biggest issues I see is that when new technology training is provided, it's often aimed at the engineering staff who attend rather than the technicians.