Fiber Networking for PLCs

  • June 30, 2020
  • Softing Inc.
  • Sponsored
Fiber Networking for PLCs
Fiber Networking for PLCs

So, you're designing your PLC Ethernet network, or maybe you are rethinking your network due to some recent network outages or IT type complexities that are giving you some serious headaches.  You thought the only way to network together Ethernet PLCs and Ethernet devices was to buy managed IT switches, which is fine, but you work with PLCs every day, and would like to eliminate the IT complexities that are not required for the plant floor.
Maybe for your network…

  • you have some long distances between PLCs or field devices, so you are thinking fiber
  • you have critical networks, so you are thinking redundant fiber, but don’t want to introduce the complexities with redundancy
  • maybe you need fiber due to EMI issues you have, or foresee
  • you want a redundant fiber backbone, and will be connecting copper Ethernet field devices
  • you want maintenance to be plug and play, even for your redundant network
  • you have unique plant floor needs like hazardous areas, multiple industrial protocols, high performance
Phoenix Digital network communications solutions solves these unique industrial challenges.  Since Phoenix Digital networking solutions are built-for-purpose, they self-recover when a fiber is broken or power is lost to a device.  They are plug and play if a communications device fails.  They are also plug and play when installed; no software configuration required.  The network requires a designated master, so there’s a one dip switch set for this; that’s it!
This simplified Ethernet network communication solution is only possible because the modules were built for the single purpose of connecting Ethernet PLCs and Ethernet field devices in critical networks.
Networks for PLC have different challenges than the business network:
  • Network downtime for production is costly, even for seconds, which is different than the office
  • Adding redundancy introduces complexity
  • Flexible configuration of an IT switch can introduce implementation and support issues for OT
  • Plant floor EMI can introduce noise on networks from a rats-nest of cables
  • IT switches are not suitable for hazardous areas
  • No support for multiple industrial protocols
The Phoenix Digital communications modules solve these challenges
  • Redundant fiber backbone between PLCs; copper RJ-45 between PLC and connected field devices
  • Redundant by design and industrial to Class 1 Div 2
  • Patented plug and play, high performance, and self-healing maximizes uptime
  • Transports Ethernet TCP/IP, Ethernet/IP, PROFINET, and Modbus TCP, at the same time
  • Form factors include in-chassis module for ControlLogix, CompactLogix, SLC-500, and PLC5. DIN rail mount for Ethernet field devices, PLCs, and DCSs.
Finding the right fault-tolerant network solution for your application

Fault-tolerant, redundant, resilient industrial networking is critical in a wide range of applications.  Some of the more common uses for industrial networking include:
  • Networking devices within a control panel
  • Networking between control panels
  • Networking in an MCC and between MCC Sections
  • Networking devices outside the cabinet
  • Networking zone to zone
The methods for creating fault-tolerant networking are nearly as numerous as the applications. Here’s a rundown of some of the most prevalent industrial networking solutions.

Device Level Rings

Device level rings, or DLR, connect Ethernet from one device to the next in a ring. Non-DLR devices must use an E-TAP (a two-port switch) or another switch with DLR embedded to connect. In a ring, communications are maintained when any one line or device fails, with a 3ms convergence time.

Device rings make sense for in-cabinet device networks and for some outside cabinet device networks, when most of the devices support DLR. They may not be a good fit when the network includes more than one protocol or there are many non-DLR devices that require an E-TAP, which adds to the expense of a project. Device rings also can create issues with lock-out tag-out scenarios.

Switch Rings

Switch rings, which are basically a ring of switches, include REP, MRP, Hirschman HiPER ring and Moxa Turbo ring. These require managed switches that can be configured for specific switch ring technology. Depending on the setup, convergence times can vary from 20ms to 300ms.

Switch rings make sense for networking cabinet-to-cabinet, MCC section-to-section or zone-to-zone when some resiliency (one point of failure) is required. It can work with some outside cabinet device networks or when multiple networking protocols are present, lock-out tag-out is required or multiple ports are needed. They may not be a good fit for in-cabinet device networks or when zone-to-zone across subnets is required. Other issues include when faster RPIs are required and when multi-cast traffic is used or when configuring with CLI (command line interface) or using a managed switch configuration aren’t practical.

Dual Networks

Dual networks (PRP/HSR or FTE) provide two independent networks running to each device or to a three-port switch with PRP embedded. These require managed switches that can support PRP technology or products with embedded PRP technology. Because two independent networks are transmitting the same information, dual networks can survive multiple points of failure on the network with 0 convergence time.

Dual networks make sense when network redundancy is required to survive multiple points of failure and when individual device redundancy is not required. They also work when multiple networking protocols are in play, lock-out tag-out is required or an extremely fast failover is necessary. Dual networks may not be a good fit when communications must cross subnets or when topology infrastructure cost or network management becomes a challenge.

Dual Rings

A dual ring, like the Phoenix Digital system, works well in stand-alone or in-chassis applications. Communications are maintained during multiple automation device failures, multiple fiber breaks and single module shutdown, with 0 convergence time.

A dual ring makes sense for networking cabinet-to-cabinet, MCC section-to-section, zone-to-zone and some outside-cabinet device networks. It’s suitable when multiple networking protocols are present or lock-out tag-out is required. Dual rings also make sense when configuring with CLI (command line interface) or a managed switch isn’t practical and when fast boot up is required. They may not be a good fit for in-cabinet device networks or when a precision motion control network is required or when zone-to-zone networking across subnets is necessary.

The decision on which industrial networking solution is right for your application depends on:
  • Topology
  • Installation/operation
  • Failure modes
  • Cost

If you’d like more information now, please contact us today, and we’ll be glad to answer your industrial networking questions.

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