OT: DCS system field instuments and fieldbus

danw said:
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.
Click to expand...

Thanks for the input, i did know HART is slower
 
kdcui said:
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.
Click to expand...

This is what i have been thinking also or maybe use AS-I where it can be used..
 
Just to clarify: there are millons of HART I/O points in DCS systems and high end PLC systems that use the 4-20mA analog as the process variable and HART for slow update secondary variables, configuration, and diagnostics. Remote I/O comm is approaching the mature stage and tends to be reliable.
 
danw said:
Just to clarify: there are millons of HART I/O points in DCS systems and high end PLC systems that use the 4-20mA analog as the process variable and HART for slow update secondary variables, configuration, and diagnostics. Remote I/O comm is approaching the mature stage and tends to be reliable.
Click to expand...


I had a good one on HART where a fluid transfer would happen into a reactor and the density of the raw material was being monitored and would alarm/trip if not at a certain point. The 4-20mA would meter in the charge, the density came in through HART.



Density was checked to ensure that the correct raw material delivery had the correct dilution and it was the first charge onto the reactor. Actually taking samples of that stuff is too risky.
 
Keta- said:
It isin't decided yet..but my guess is it Will be an dcs
Click to expand...
In that case I would say that you need to wait until the DCS is decided. Then, based on what the DCS supports, you can decide the network for the field.
It is a safe bet that HART will be supported by any modern DCS.
You mention that when possible you would like to use ASi. I imagine this would be for non-intrinsic safe areas where you need discrete IO. In this case the DCS would need to support Profinet controller or EtherNet/IP scanner and you can find in the market ASi gateways compatible with these protocols. IO link would also be possible to use in non-intrinsic safe areas, by means of EtherNet/IP adapter or PROFINET IO device gateways what support multiple IO lionk master channels.
 
AlfredoQuintero said:
In that case I would say that you need to wait until the DCS is decided. Then, based on what the DCS supports, you can decide the network for the field.
It is a safe bet that HART will be supported by any modern DCS.
You mention that when possible you would like to use ASi. I imagine this would be for non-intrinsic safe areas where you need discrete IO. In this case the DCS would need to support Profinet controller or EtherNet/IP scanner and you can find in the market ASi gateways compatible with these protocols. IO link would also be possible to use in non-intrinsic safe areas, by means of EtherNet/IP adapter or PROFINET IO device gateways what support multiple IO lionk master channels.
Click to expand...
I think it will be a Siemens system..
No instrict safety needed.. trying to figure out for future. What would be the optimal choice.
 
Keta- said:
I think it will be a Siemens system..
No instrict safety needed.. trying to figure out for future. What would be the optimal choice.
Click to expand...
Siemens has both, DCS and PLC systems.
If there are no intrinsic safety requirements, then I would advice you think of PROFINET IO devices, as this is the protocol supported natively by Siemens. With PROFINET IO it is very easy to integrate AS-i and IO Link. I would not recommend HART in this case. The ecosystem of PROFINET IO devices is vast, and because the conformance test is so stringent and "Teutonic" (as somebody qualified this conformance test process in a different post), the risk of interoperability problems is as close to zero as it can get.
 
Keta- said:
I think it will be a Siemens system..
No instrict safety needed.. trying to figure out for future. What would be the optimal choice.
Click to expand...


Ethernet in my opinion. Also, it's been a while since I used Siemens, but the last conversation with someone there, they mentioned that Remote IO network adapters that worked on fiber optics were coming out. I've used the Rockwell equivalent and it's pretty good too.



If you use valves, I'd look at Burkert's ET200 offering. Though for a brand new plant this may not be that useful.
 
mostly depends on the brand of the control system and the process that needs to be regulated.
The use of HART is still widespread. I wouldn't trust contractors to route Ethernet away from high voltage/current cabling and a lot of motors close by.
 

Similar Topics

M
Bailey infi 90 DCS system Composer unable to establish communication with ICI
I have Bailey infi 90 DCS system The composer (EWS) was unable to establish communication with ICI . I got this error message anyone has any...
Replies
0
Views
472
mmmly2002
M
I
Micro wave radio recommendations needed for remote dcs to scada system data comms
Hi Guys, What Radio Device will be appropriate to send a DCS Data to SCADA System of two separate remote control rooms?
2
Replies
18
Views
5,168
IdealDan
I
R
Difference between SCADA system and DCS system
hi! i am quite confused about SCADA and DCS.. is there any differences between the two systems?. thanks for the info..
Replies
6
Views
2,344
danw
danw
huynt
Migration PLC5 Ethernet to Controllogix with ethernet port connect with DCS system
Dear all, I has a PLC5 system with PLC 5/80 CPU with 1785-ENET want to migrate to Controllogix. PLC5 system connect with DCS over Ethernet port of...
Replies
8
Views
5,634
osmanmom
O
R
configuration of s7 400 & s7 300 plc's for a little DCS system
please help me to buy a set of s7 400 and s7 300 for my laboratory. we want to have a pcs7 hardware configuration for making a little and low cost...
Replies
7
Views
4,794
redautomation
R
Back
Top Bottom