Foundation Fieldbus related issues

[krecian]

Has anybody come across the following in real life FF system,

1. what type of hardware failures are normally observed?
2. what is the avergae number of devices that are practically installed per segment?
3. what is the average power drawn per device?
4. are there any specific failures related to linking devices? If yes, how were they resolved?
5. How often the 'noise' has affected the communication and outage in the plant or part of the plant?

With reference to APC packages along with FF systems,

1. does the APC (sitting on HSE bus)execute through the host computer or directly to field devices?
2. what is the average "on-line" time of APC?
3. are there any demands or restrictions imposed by APC on the hardware that have been discovered after implementation?


thanks,
KRECian

 

[controlnovice]

Krecian,

1. what type of hardware failures are normally observed?

No more than any other instrument using HART. As far as the Fieldbus connection hardware - I still haven't seen anything out of the ordinary. Actually, no failures so far in about three years.

2. what is the avergae number of devices that are practically installed per segment?

I'd say our average is about 6-8 per segment. But mostly due to location of the instrumentation itself - not due to current draw or distance. It's just easy to run the wire to one location that has 6-8 instruments, rather than try to fit as many on one segment as you can. Plus, it leaves room for growth.

3. what is the average power drawn per device?

I don't have information on this. Each manufacturer should have a rating. I think I've seen less power draw on the instrument than the manufacturer states.

4. are there any specific failures related to linking devices? If yes, how were they resolved?

Failures? Haven't seen any. But getting them to 'link' in the first place can be time consuming.

5. How often the 'noise' has affected the communication and outage in the plant or part of the plant?

No noise issues at all. With digital communication, one shouldn't see noise issues. I suppose it's possible, but we haven't seen any.


Sorry I don't have info on an APC package.

ControlNovice

 

[Rheinhardt]

HI Krecian,

i found the following on net it is a comparison between FF and conventional systems

http://zone.ni.com/devzone/conceptd.nsf/webmain/DD9137E0DD677BA28625687C0000EC9B?OpenDocument

I feel it is a pretty well structured control system for process applications.
Are you looking to install, upgrade a new FF system?, it will make fault finding a lot easier, i always go for remote IO systems (BUS systems) less cables easier tracking, only concern is that your maintenance technician needs to be clued up with the software for diagnostics on instrumentation, and must be the person mostly invoved in the installation, like any new-technology equipment it will be a learning curve but the bus philosophy should stay the same, i would prefer this over any type of local IO.

Kind Regards

 

[krecian]

Thanks very much, controlnovice and Rheinhardt for your inputs.

Yes, I am going to work on a new FF system for a gas processing plant. My questions were with the intent of knowing operational/maint related issues that can be taken care during the initial design/engg stage.


KRECian

 

[veec]

Krecian,

WE had a lot of failures initially to do with the power interface cards, cured with an upgrade.
FB devices are more expensive than 4-20mA ,perhaps less units manufactured, so far, has something to with it.We found the part required for a device were so expensive it was better to order a whole new FB device.
If you lose a drop you will lose all the devices on that drop, similar to a PLC/DCS outputcard total failure.
If you go for an IS system then the number of instruments on a drop should be no more than 3.
If a single field device suffers immediate failure and loses communication, your options to fault find can be limited to swopping out the device.
No noise problems.
FB was not at all popular with our maintenace team, who would have gladly swopped it all out for Hart 4-20mA.
Im not entirely sure if FB devices can be used on a
Shutdown SIL rated system,either.
veec

 

[controlnovice]

Krecian,

VEEC is right. FB devices are more expensive. Engineering is more expensive (a little more complicated than standard 4-20HART).

If you loose a drop, you will loose all instruments on that drop. For instrinsic safe instruments, we found a solution that allowed us to keep the traditional 8 - 10 devices per segment.

FB is not popular with maintenance in all the installations I've done. I do not recommend FB on any of our plants unless the plant has an engineer and maintenance team willing to put in the extra time to learn it.

 

[krecian]

Well, thanks, vvec and controlnovice. That's some more value-addition.

krecian