OT: DCS system field instuments and fieldbus

[Keta-]

Hi all this is bit ot but here goes..

What kinda fieldbus you use / would use if youre going to build new installations on youre process..

Is Hart still valid? Or the "New ethernet/ip" that is going to the instrument level? What would you prefer or just simply use traditional analog i/o?

Im thinking of the instrument level here not vfd's etc..

Thanks for the answers!

 

[cardosocea]

Depends an awful lot on the brand of the control system and process to be controlled too.



HART is still very much used. I wouldn't trust Ethernet with a bunch of motors nearby and trusting contractors not to route it next to high voltage/current cabling.

 

[JeremyM]

I’ve come to trust Ethernet 100% around very noisy stuff.

I only trust RS-485 92% of the time. 67% of my distrust comes from other engineers ignoring my pleas to use shielded twisted pair cabling. That happens 86% of the time.

 

[Robb B]

Any data run in anything other than a house (and even then!) should be shielded. The physical design of ethernet (cat 5/6, no experience with 7 or 8 yet) is very good at preventing induced signals, the shielding just guarantees that. I would like to see a move towards PoE (Power over Ethernet) based instruments, possibly working on HART or CIP.

 

[drbitboy]

I’ve come to trust Ethernet 100% around very noisy stuff.

I only trust RS-485 92% of the time. 67% of my distrust comes from other engineers ignoring my pleas to use shielded twisted pair cabling. That happens 86% of the time.

and 42% of all statistics are fabricated on the spot .

 

[JeremyM]

and 42% of all statistics are fabricated on the spot ;-).

We can safely make it 44%.

 

[g.mccormick]

We can safely make it 44%.

9 out of 10 dentist agree.

 

[AlfredoQuintero]

Hi all this is bit ot but here goes..

What kinda fieldbus you use / would use if youre going to build new installations on youre process..

Is Hart still valid? Or the "New ethernet/ip" that is going to the instrument level? What would you prefer or just simply use traditional analog i/o?

Im thinking of the instrument level here not vfd's etc..

Thanks for the answers!

The new APL, or advanced physical layer, specification allows intrinsically safe instruments to communicate through EtherNet/IP over APL, PROFINET IO over APL, etc. ODVA and PI associations are working on their conformance test specifications to include testing for APL enabled devices. It seems in a few years there may be a decent numbers of APL-capable devices in the market place. I do not think this is the case at the moment though.
Another possibility is to consider HART, by means of HART IP/HART master, or using EtherNet/IP adapter-HART master technology, for which Rockwell has some offering if you are thinking of Rockwell systems. For Siemens useres there are PROFINET Device/HART master devices.

At this point in time Foundation Fieldbus and PROFIBUS PA do not seem to be the recommended choice for a new plant, as these technologies are being replaced by APL.
Hope this helps.

 

[Keta-]

The new APL, or advanced physical layer, specification allows intrinsically safe instruments to communicate through EtherNet/IP over APL, PROFINET IO over APL, etc. ODVA and PI associations are working on their conformance test specifications to include testing for APL enabled devices. It seems in a few years there may be a decent numbers of APL-capable devices in the market place. I do not think this is the case at the moment though.
Another possibility is to consider HART, by means of HART IP/HART master, or using EtherNet/IP adapter-HART master technology, for which Rockwell has some offering if you are thinking of Rockwell systems. For Siemens useres there are PROFINET Device/HART master devices.

At this point in time Foundation Fieldbus and PROFIBUS PA do not seem to be the recommended choice for a new plant, as these technologies are being replaced by APL.
Hope this helps.

Thank you, this helps.

 

[Keta-]

Depends an awful lot on the brand of the control system and process to be controlled too.



HART is still very much used. I wouldn't trust Ethernet with a bunch of motors nearby and trusting contractors not to route it next to high voltage/current cabling.

So HART would be the prefered choice?

 

[danw]

HART runs on 4-20mA, so HART means the field device also has 4-20mA.

Getting process variables in real-time through HART is not practical for many processes because real-time HART is a 2 updates per second protocol with high end analog input hardware that includes a HART modem. HART is just too slow for some control.

4-20mA update on the field end is typically at about 5-10 updates per second from 'smart' transmitters (depends on model/brand), dumb analog transmitters can have millisecond update response.

HART is the primary means of configuring and troubleshooting field instruments using Windows software and a HART modem, a handheld communicator, or high-end Asset Management software.

I've seen coriolis meters with Ethernet/IP where it makes sense to get more than one process variable out of the flowmeter. But I do not know what the effective update rate is for Ethernet/IP.

4-20mA is robust when wired with STP and can be maintained by almost any electrical guy.

 

[AlfredoQuintero]

Thank you, this helps.

What system are you planning to use? DCS or PLC?

 

[kdcui]

Coming from a previous position at an OEM (Biotech / Pharma):
Our systems were originally built with PROFIBUS. Nothing but complaints from customers. Terminating resistors not set correctly or not working, etc.

The trend and customer feedback has been to try and put everything on a Ethernet based protocol as much as possible. Most big companies have been doing this and expect their vendors to comply.

We eventually went E/IP (since we were a Rockwell house) and didn't look back. The tradeoff was that a bit more complexity and attention to network design is required. We needed a fairly comprehensive assessment to make sure the Ethernet network was secure - the product team implemented a whole VLAN and NAT scheme to ensure "universal compatibility" with outside networks.

Working in a new position now where we are bring most IO back as traditional signals into distributed IO blocks, and everything is PROFINET back up to the controller.

 

[mk42]

What system are you planning to use? DCS or PLC?

This is a key question. Most protocols are similar enough that ultimately what brand your controller is usually 90% of the decision making factor in this. Start with what the PLC/DCS supports and work from there.

Agree with the consensus that Ethernet comms wherever feasible is the best plan (and remember that ethernet over fiber instead of copper is pretty seamless whenever you need long distances). As stated, the complication is at the field device level, where the Ethernet APL is just starting to get rolled out, and there isn't much industry support yet.


I'm a big fan of IO-link in the machine space, not sure how that plays into the process field.

 

[Keta-]

What system are you planning to use? DCS or PLC?

It isin't decided yet..but my guess is it Will be an dcs