Controlnet Intermitent communications loss

[Welsyntoffie]

Hi

We are running a control logix PLC system with controlnet. The controlnet has 12 nodes. Uses fiber in between the fiber repeaters .

My main question is about the setup. I noticed in the logix 5000 studio tree that all the electronic keying is disabled. All revisions are are set to 3.1, but the field devices are 4.3 and higher.

NUT = 20ms

ACN RPI = 80ms

IO RPI = 160ms

Current installed Configured (PLC)
Node Revision Type Revision Type
15 4,3 ACN15/C 3,1 ACN15/C
16 10,2 ACN15/D 3,1 ACN15/C
19 4,3 ACN15/C 3,1 ACN15/C
20 4,3 ACN15/C 3,1 ACN15/C
21 4,3 ACN15/C 3,1 ACN15/C
22 4,3 ACN15/C 3,1 ACN15/C
23 5,1 ACN15/C 3,1 ACN15/C
24 4,3 ACN15/C 3,1 ACN15/C
25 4,3 ACN15/C 3,1 ACN15/C
26 5,1 ACN15/C 3,1 ACN15/C
27 10,2 ACN15/D 3,1 ACN15/C
28 4,3 ACN15/C 3,1 ACN15/C


Can this setup cause intermittent communications failures. Comes ON for a second then goes offline (Image attached of trend) Not every day and not every week.

We sometimes go for a month without a problem and then it starts. Could last for several hours to a couple of days and then go back to normal operation by itself.

Fiber has been tested, all cables and connectors has been checked and cleaned.



PLC is setup, when device fails then set the analog value to full PV. Thats why the spikes are so clear.

So can "Disable keying" and mismatch revisions cause this problems?

Node 16 is the only node reporting Collisions. They start off small value then grows to about over 240 then resets to zero and starts counting.

Trend and diagnostic results are not from the same day

 

[gclshortt]

http://www.plctalk.net/qanda/showthread.php?t=96914

The above thread may help you out.
Regards,

 

[Welsyntoffie]

I did read that thread. Does not really apply to my situation.
We loose random connections throughout the whole controlnet system, not just one or two inputs. Only 1 ACN15 is showing collosions (node 16).
Another tech assumes the fiber might be cracked somewhere. It's an underground mine. So during blasting time the fiber might move either out of position or into position. But the trend shows the problem resolved itself before 13:00 and the blast time is 18:00. No other blasting may take place before 18:00. You will be jailed if blasting before everyone is clear.