Plug in to standard solutions

Senior Technical Editor Dan Hebert notes that there is no single vendor or independent organization that promulgates Ethernet standards and that end users must modify commercial standards for their own use.

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 By Dan Hebert, PE, Senior Technical Editor

M

ost industrial facilities contain several types of industrial networks. Ethernet has become the most common industrial network, and other specialized and more proprietary networks are used depending on particular applications.

Specialized networks are supported by vendors or by independent organizations such as Fieldbus Foundation, Open DeviceNet Vendors Association (ODVA), and Profibus Trade Organization. These vendors and organizations provide network standards that help end users with purchase, installation, testing, and maintenance.

For Ethernet in industrial applications, there is no single vendor or independent organization that promulgates standards. End users must instead modify commercial Ethernet standards for their own use.

The Electronic Industries Alliance and the Telecommunications Industry Association collaborated on specifications for installation and test of Ethernet networks. Although originally created for commercial Ethernet networks, these specifications can also be used for Industrial Ethernet installations with only minor modifications.

The EIA/TIA-568 Standard includes EIA/TIA-568-B.1 General Requirements, EIA/TIA-568-B.2 Copper Cabling Requirements, and EIA/TIA-568-B.3 Fiber Cabling Requirements. There are also other requirements for more specific issues. Similar ISO and IEC specifications exist such as ISO11801.

A Structured Cabling System can be created by following a standard methodology defined in the EIA/TIA 568 requirements. These requirements specify a generic telecommunications cabling system for commercial buildings that will support a multi-product, multi-vendor environment. “If one follows these installation standards and uses EIA/TIA compliant cabling products, the networking equipment will work as designed with no surprises and no performance issues,” says Don Wiencek, president of B&B Electronics Manufacturing.

According to Wiencek, there are very few changes needed in the Structured Cabling System requirements for industrial environments. All the same standards apply including installation requirements and test requirements. “If everything is mounted inside NEMA-rated enclosures, then nothing changes at all,” reports Wiencek. “However, if you want to plug into the network from outside an enclosure, there is a connector style available called Industrial RJ-45. Specifications for this connector are being developed by the EIA/TIA TR-42.9 Committee and by ODVA for Ethernet/IP applications and are nearly complete.”

Because the main differences between a commercial Ethernet network and an industrial Ethernet network are cables and connectors, this is a main focus area for Industrial Ethernet standards.

“ODVA has created specifications for connector interfaces and communications requirements for devices, and they are in the process of creating specifications for Ethernet cable in the industrial environment,” says Komal Mehta, senior product marketing manager at Harting.

ODVA’s EtherNet/IP standard also addresses connectivity and installation challenges. “It identified and approved two types of connectors: Circular M-12 D-Coded (4-pin) and RJ-45 (8-pin) with IP67 protection,” adds Mehta. “EtherNet/IP will certify products via conformance testing. For end-users, this will greatly reduce the burden of compliance and interoperability of different hardware and software product provided by different suppliers.”

Because the physical layer is common to most versions of Industrial Ethernet, the ODVA standard for physical components such as cables and connectors might have wide applicability.

Both M-12 and RJ-45 connectors can be used in industrial Ethernet installations, there are important differences. Because RJ-45 connectors are standard for commercial Ethernet installations, it was logical to adapt it for industrial environments. The most common approach is to protect the RJ-45 connector by encasing it in a molded housing. With this technology, some manufacturers have been able to achieve IP67 and IP68 ratings.

This is the same degree of protection provided by M-12 connectors, but the RJ-45 plug originally was designed and produced to work in an office environment. The M-12 was designed from the ground up for harsh factory environments.

According to Bernie Baruffalo, senior engineer with Lumberg, when you compare RJ-45 to M-12, you’re comparing the relative strength of a connector made of plastic (RJ-45) with the relative strength of a connector made of metal (M-12). “In terms of durability, toughness and strength, the metal connector is going to possess vastly superior characteristics to enable it to function with a higher degree of success on the factory floor, states Baruffalo.”

Besides a more rugged material of construction, other elements such as epoxy sealing, heat shrink tubes, and full copper foil shielding make M-12 connectors superior to RJ-45 connectors for industrial environments. But since RJ-45 connectors are much cheaper than M-12 connectors, it often makes sense to make appropriate use of both in an industrial application.

Pull: The RJ-45 plug originally was designed and produced to work in an office environment. The M-12 was designed from the ground up for harsh factory environments.

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