Ethernet Quality

Intech01

Member
I
Join Date
Apr 2007
Location
Pasco Washington
Posts
3
I’ve had PLC5 DH+ for years. I daisy chain the DH+ from processor to processor this work for five years no problems, but adding on cable length (not over 10,000’ 57.6 allowed) plus connections degrading and more data small problems and glitches started occurring. After several downtimes the cost of downtime far exceed the cost of doing it the higher quality way. Using Allen Bradley trunk line type with drops no more problems. Now we are adding. The new part of the plant uses control logix and Ethernet. It was my suggestion that we use good quality shielded Ethernet cable plus industrial Ethernet type switches and connectors. We have a lot of vibration plus electrical noise and sometime power surges from the power supplier. I’m told by IS and corporate that what I want to do is overkill. Just would like other plant control people opinions.
 
What is the cost difference between the "Allen Bradley trunk line type with drops" and the "good quality shielded Ethernet cable plus industrial Ethernet type switches and connectors"? If it is $5000 or less for 10,000 feet, then it will have a short payback, as shielded cable will prevent noise interference, and everyone seems to gradually migrate to the Ethernet protocol.
 
My rule of thumb is :

If the ratio of installation to material cost is significant, then its better to spend a little bit extra for materials because its cheaper to go over board than to be marginal and have to pay to get it replaced with a better grade.

Typically ethernet cable is a very small portion of the total cost even if it is over $1 per foot.

As for industrial ethernet switches, so far I have found nothing to justify the added cost. If you let IS pick the switches, then they will be more willing to take responsibility for them.
 
Last edited:
Archie said:
As for industrial ethernet switches, so far I have found nothing to justify the added cost. If you let IS pick the switches, then they will be more willing to take responsibility for them.
Click to expand...

Yes, but will they take responsibility at 2:30AM ( Thats 2:30 in the MORNING)?
 
It really depends on what your downtime is worth.
You can use Walmart switches and it may work perfectly forever, but if the factory is down for an hour and that cost is worth say $250,000 then quality industrial managed switches are cheap insurance.
The IT departments experience is in office applications where no-one is concerned if secretary A's email takes 30 seconds to get to secretary B. (It is probably only about what they did last weekend anyway). If you are controlling a process and you have a lag of 30 seconds then you can be in big trouble.
Regards Alan Case
 
We have both networks in our facilities.

1. We have chosen to utilize ethernet with ControlLogix due to availability and speed.
2. On our critical controllers that we deem that we cannot lose communication with, we deploy a failover communication scheme that will utilize DH+ in the event of ethernet loss.

Since we are not on the corporate lan (we use our own control lan), we have not had any issues with communication loss on ethernet.

Just something to consider.
 
If comm is lost, switch to DH+. Retry ethernet periodically. If successful, switch back to Ethernet.
 
Sorry I've been pretty busy since this post I really appreciate the feedback. You've had some valid points. I do like the IS managing the switches but I know they won't be available when needed unless they change their mindset. One problem that I run into is some people install less expensive hardware and cable think that everything is ok but it comes back to bite them later on when loads increase distances become greater connections begin to fail. The DH+ was fine for five years, then all kinds of problems, we redone the cabling 12 years ago not a problem since. The other indication I found that maybe industrial is worth it is equipment comes in with there own backplane and computers. Side by side in the same environment the industrial plc's have by far fewer hardware problems than their proprietary computers. I'm just not sure they are industrial enough for our environment.

 

Similar Topics

A
reading data from siemens controller (profinet) to ethernet/IP controller
Hello I have a s7-1200 and I would like to read the tags present in this controller with my controllogix controller. The two controllers don't use...
Replies
4
Views
82
JesperMP
JesperMP
K
use Simotion D ethernet port as gate to access S7-1500 plc program
Can we use a Simotion D455 ethernet port x127 as a gate, to access S7-1500 plc Tia Portal program ? In the Simatic manager, we used Netpro to do...
Replies
2
Views
84
mk42
M
S
Powerflex 755 - Hardwired & Ethernet in Parallel
So I have a sort of unique situation where I'm wanting to run a PF755 from the IO and over ethernet. Of course, this comes with it's own set of...
Replies
9
Views
259
sparkie
S
afm
Ethernet Dongles for PC-to-PLC connection?
Hi all, My ethernet port on my laptop recently broke and I was hoping to just use a usb-c dongle in the mean time to go live on my PLC until I...
Replies
14
Views
453
JesperMP
JesperMP
A
Ethernet comm problem with PLC when inverter enables.
Hi; In a cabinet of a machine, a Fatek PLC with an Ethernet communication card is working. In the same cabinet, there is a 1 kW inverter. When...
2
Replies
16
Views
499
Gleichner33
G
Back
Top Bottom