Aboveground F.O. Cable Routing

[ThePunisher]

We are working on a project where the client standards are ambiguous with regards to fiber optic cable installation. Presently, we are running our electrical and instrumentation cables on separate above ground steel cable trays to the process building. The process building is all-steel structure typical for ore crushing process.

There are two sets of fiber optic cables (Profibus DP and Condition Monitoring) routed to form a ring back and forth to the PLC controller at the process substation. Our proposed path is to:

1. Route these fiber optic cables in a separate tray from the power cable and instrument cable trays.

2. To obtain redundancy, one leg of the ring will go to one tray and the other leg (return cable) will go to another tray.

Will it be logical to route these two sets of FOCs in separate trays instead?

Aside from the bending radius requirement, are there any general requirement for FOCs installed in trays? Will conduit installation instead better?

What extent of installation should be done to ensure redundancy of FOC cables (forming a ring network)?

We are presently contacting a FOC vendor for advise but appreciate much if we can be guided here.

Your abled experience and exposure is highly appreciated.

 

[MikeHalloran]

Aboveground installation leaves the FO susceptible to physical damage from errant rocks of all sizes, and from heavy equipment. Neither cable trays nor conduit will likely make a difference in the outcome of any such encounter.



Mike Halloran
Pembroke Pines, FL, USA

 

[controlsdude]

fiber optic is immune to power cables versus just regular instrumentation cable. So running the fiber in the power tray is not a problem.

 

[ThePunisher]

Thank you Mike. We have initial concerns on that. However, the condition monitoring cabinets are located at certain building elevations and at different locations within the buildings. We will try to propose underground route through concrete encased ducts. However, the risers should go through conduits.

Any other possible suggestions?

 

[Chiprme]

This doesn't sound like a major problem.

If there's a special mechanical strength need try someone like optical fiber corp ( occfiber.com ); they make tactical cables for the military.

 

[MikeHalloran]

It may be simpler to just assume that there >will< be incidents that break the FO, and take steps to minimize the impact of the incidents.

I.e., set up the system to shut down gracefully when the fiber goes away,
and prepare several sets of replacement FO cables,
and designate and train individuals in rapid deployment of the replacements,
and designate and train other individuals to manufacture or order replacements for the replacements,
and document all of that,
and back up the documentation.

OR

Lace the fiber to/through an elevated trellis of ridiculously oversized structural steel.

OR

Use line of sight lasers instead of fiber.

OR

Use wireless instead of fiber.

OR

Use copper (replaceable and repairable by ordinary tradespeople) instead of fiber.



Mike Halloran
Pembroke Pines, FL, USA

 

[waross]

I have seen several fiber installations in 4" rigid conduit. The thinking is that it takes a lot to damage 4" rigid conduit. (Same dimensions as sched. 40 pipe.)
Separate trays or conduits makes more sense if the routes are widely separated. I would consider at least 2" or 3" rigid for mechanical strength and protection. We had to get a portion of a plant under construction on line and could not wait for the installation of the fiber. One of the tech guys ran a piece of RG-8 coaxial cable temporarily. He was able to source appropriate modems to interface with the DCS system. The coax worked fine until the fiber arrived. Very few industrial plants really need the bandwidth of fiber. You may consider exploring a coax option as a way to effect emergency repairs to get back online until a damaged fiber is repaired. The coax was more or less free run through the mill. It doesn't have to follow the fiber route, leaving room for repairs to fiber conduit if needed.

Bill
--------------------
"Why not the best?"
Jimmy Carter