The increasing use of digital equipment in industrial environments coupled with increased integration and data bandwidth requirements has led to growing adoption of Ethernet (IEEE 802.3) for communication in place of older serial-based communication systems.
However, simply selecting ruggedised versions of Ethernet equipment originally designed for conventional IT environments will not create a true Industrial Ethernet network.
Ruggedness is important, but it is only one part of a much larger picture. An excessive focus on particular physical characteristics such as temperature and vibration specifications leads to other critical factors being overlooked, and hence inappropriate purchasing decisions.
System-wide considerations have a bigger impact than the physical characteristics of an individual component. Fitting a race-tuned engine to an otherwise standard car will improve its performance, but it won’t match a fully prepared racing car with the same engine.
Power and torque are only part of the story — suspension, brakes, tyres and so on all contribute to how quickly the car can get round the track and whether it will last the distance.
A racing car also needs features for quick repairs or replacement (for example, the single nut securing a wheel to the hub instead of the four or five used on most road cars) and remote monitoring and diagnostics to ensure success.
Similarly, Industrial Ethernet is about the entire network. The physical network consists of cables, connectors and active components such as switches and routers, all of which affect end-to-end signal transmission.
A deep understanding of how they work together allows the design of a network that will operate effectively under the challenges of an industrial environment.
The physical design must also be complemented by an equally well thought out logical design including addressing and segregation.
Other critical factors that must be considered include ease of configuration and diagnostics, network and cyber security, network management tools, redundancy protocols, automation integration, and remote access.
It is important to consider the total lifecycle of a project from initial design through engineering, commissioning, operation, maintenance, and any later upgrades or expansion.
Physical specifications are important to the initial design process, but other factors will arise later in the total lifecycle, especially during operation, maintenance, expansions and upgrades.
Proven reliability and maintainability are also more important than bandwidth alone for automation and control systems, whether you are coming from the perspective of occupational health and safety or the need to avoid production downtime.
Many industrial environments recognise that the personnel who will operate and maintain the network may not be IT specialists, and are then tempted to install basic unmanaged network switches in the name of simplicity.
Pictured above: A top down plant overview of a complete industrial ethernet network.
With advancements in Industrial Ethernet today, a case can readily be made for products that come with web-based, graphical, easy to use software configuration and diagnostic interfaces, and with options that can be set via DIP switches, which are familiar to the electricians likely to be charged with installation and modifications.
Although it may be acceptable to shutdown part of an IT network for a period of time (for example to install additional network equipment), that luxury is rarely open to the person in charge of a factory or process control network where 24×7 operation is the norm.
This also impacts on maintenance: while mean time to failure is an important statistic, mean time to repair is crucial, especially as Murphy’s Law dictates that any failure however unlikely will occur at the most inconvenient time and location.
Where IT equipment is usually replaced on a three to four year cycle, the components of an industrial network can easily be in operation for 10 years or more.
If you need to replace a faulty device after several years, will the backup of its configuration be easily retrievable?
Will the replacement have the same firmware to ensure site-wide compatibility?
Can the old firmware and configuration be saved and restored from removable media without involving a computer?
How long will expansion modules (for example, additional ports) be available for the base unit you purchase today?
How long will the supplier provide a repair or replacement service in the event of hardware failure?
Some vendors have a total lifecycle perspective of the Industrial Ethernet network solution intended for industrial environments, while others plainly stop at physical ruggedisation.
A sensible approach to Industrial Ethernet design and implementation is to start by understanding the application and site-specific issues.
Begin by considering the physical environment and some basic architectural issues. Will the network hardware be installed in 19-inch racks, DIN rails or a combination? What are the available power supplies at that location? What is the temperature range?
Are there any airborne contaminants (such as the hydrogen sulphide present in water treatment plants) that may be conductive or corrosive?
How much bandwidth will be required? Where and how will the physical cabling be run? Is fibre or copper cabling more appropriate due to distances or electromagnetic interference?
Then consider an appropriate network topology (e.g ring, star or a combination). Complement the physical topology with the appropriate logical network design for addressing and segregation.
Which automation system is in use or will be used? Can the Industrial Ethernet network be seamlessly integrated with the automation system?
Who will configure and maintain the network itself – IT personnel, automation engineers or electricians?
What are the network security measures to be implemented? What network management tools are proposed?
What existing network infrastructure will be retained or reused? Will a partial network migration be required, and how will the older and newer networks coexist?
Pictured above: A screen capture of a network topology.
Even something seemingly as basic as cabling deserves careful consideration. Proper physical cabling design and installation has largely been ignored as most industrial networks typically carry smaller packets of data and operate well below capacity.
However, once a network begins to grow and the utilisation increases, poor physical cabling will eventually result in performance issues and lack of scalability.
Industrial environments are often subject to vibration, dust, oil, moisture, UV exposure, and vermin, which are not usually significant issues in the typical office or data centre.
A correctly specified cabling solution should include jacket materials suitable for the environment, and factory-tested patch leads with moulded boots and suitable connectors.
Only a minority of people currently consider the comprehensive design and implementation approach described above, but a structured and total lifecycle approach to Industrial Ethernet will improve the performance, reliability, scalability and longevity of your network.
[Justin Nga is Business Development Manager, Belden Industrial Solutions.]