CR4® - The Engineer's Place for News and Discussion®


Previous in Forum: How to Make Locusts Useful   Next in Forum: Seminar Topic
Close
Close
Close
9 comments
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 13899
Good Answers: 155

State of the Art in PLC-DCS-HMI

07/27/2016 4:59 PM

Has there been any advancement in PLC wiring durability in the last twenty years? Has Fiber optic replaced hard wiring in any known applications where the environment may be somewhat harsh to hard copper wiring?

What is the most durable system possible?

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 19496
Good Answers: 1141
#1

Re: State of the art in PLC-DCS-HMI

07/27/2016 5:49 PM
__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9580
Good Answers: 457
#2

Re: State of the Art in PLC-DCS-HMI

07/28/2016 6:48 AM
__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 13899
Good Answers: 155
#3
In reply to #2

Re: State of the Art in PLC-DCS-HMI

07/28/2016 4:36 PM

Had heard of it, and it has been discussed here, but there are signal fidelity concerns, since this is a power generation facility, and there are probably many RFI noise spikes.

We have used a few control situations where the easiest way to transmit a signal (4-20 mA was too far to work properly) was RF transmitted, and this really only was used to fire up a relay that kicked in a second injection pump when the lead pump was failing to neutralize all the chlorine on an outfall.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9580
Good Answers: 457
#5
In reply to #3

Re: State of the Art in PLC-DCS-HMI

07/29/2016 4:47 AM

Agreed - signal fidelity would definitely be a concern.

I was more addressing the "State of the Art" - as in the title, than the "durability" in the actual post.

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 13899
Good Answers: 155
#7
In reply to #5

Re: State of the Art in PLC-DCS-HMI

07/29/2016 5:13 PM

That "State-of-the-Art" thingy always turns around to bite us in the .....

Most times in power generation, what shows up at a plant as new, is anything but "new" to the world of computing. I can't believe we have done what we have with even some of the older Allen-Bradley PLC's.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Power-User

Join Date: Nov 2009
Posts: 290
Good Answers: 55
#4

Re: State of the Art in PLC-DCS-HMI

07/29/2016 12:38 AM

1) Terminating the wiring is part of cabling, right? For field wiring, the screwless spring clamp terminals and terminal blocks (Wago style) probably fall in that 20 year interval. Some guys swear by them. Most older guys will concede that screw terminals loosen over time and this design is supposed to eliminate that issue.
http://www.wago.us/products/terminal-blocks-and-connectors/overview/

2) For internal PLC wiring, Bedrock Automation has a pinless backplane; that's an extreme form of wiring durability.
They seem to be marketing to those places concerned about cyber security. Discussion here, their URL is there, too.
http://control.com/thread/1464039633#1464039633

Register to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 13899
Good Answers: 155
#6
In reply to #4

Re: State of the Art in PLC-DCS-HMI

07/29/2016 5:11 PM

Thank you.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3009
Good Answers: 421
#8

Re: State of the Art in PLC-DCS-HMI

08/02/2016 12:07 PM

How long is the distance, what kind of obstacles (walls, partitions, etc.) are in the signal path, and what is the data rate?

__________________
Curious minds want to know, engineering minds get answers....
Register to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 13899
Good Answers: 155
#9
In reply to #8

Re: State of the Art in PLC-DCS-HMI

08/02/2016 4:46 PM

Let's make an example of the RO system and EDI system at the plant I am stationed at of late:

None of the signals from the PLC/HMI are transmitted further in the plant with the exception of one condensate tank on the east perimeter, about 400,000 gallon capacity.

Tank level on that is a pressure transmitter. The 4-20 mA output is actually on a boosted wire loop with a repeater at the RO PLC, which is about 50 yards away (not really all that far for current loop), but the signal also transmits to the gas turbine control cab about another 75 yards away. All of the local panels in the RO building that control pump rates, switch valves, pick up instrument signals and transmit them to the PLC are within 100 ft. As to obstacles, there is a wall of the RO building, a set of storage tanks, control building for the cooling tower (if not the cooling tower itself), all of which stand between the RO/EDI PLC and the pressure transmitter on the condensate storage tank. Within the RO builing are pipes overhead, mostly horizontal (some obviously are vertical), wire trays that could interfere with signal line of sight.

With well over a hundred switches, sensors, control bits, and calculations, each of which has its rung structure in the ladder logic, one scan takes about 2-3 seconds depending on what is taking place. It is an older Allen Bradley PLC that was probably just a few weeks from obsolete when purchased back in 1999.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Register to Reply 9 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Copy to Clipboard

Users who posted comments:

Carl_E (1); James Stewart (4); JohnDG (2); RAMConsult (1); SolarEagle (1)

Previous in Forum: How to Make Locusts Useful   Next in Forum: Seminar Topic

Advertisement