ICS network integration benefits for a connected plant

Industrial control system (ICS) insights

• Connected plants have the potential to transform manufacturing industries by bringing real-time data through an industrial control system (ICS).
• An engineer building a connected plant might be overwhelmed by the networking protocols, but a good rule of thumb is to have two or three.
• A well-designed ICS system will interface in as few places as possible while still providing the redundancy suitable for the application.

How many components does a typical industrial control system (ICS) have? Most have at least a distributed control system (DCS) or programmable logic controller (PLC) and many have both. How many include safety instrumented systems (SIS), online and offline analyzers, smart instrumentation, asset management suites and edge devices?

Connected plants have the potential to transform manufacturing industries by bringing real-time data into a manufacturing execution system (MES), which helps reduce supply chain uncertainty and increase throughput.

However, for the controls engineer tasked with building a connected plant, the challenge can be daunting. They must get all their components working together in a secure manner while not introducing excessive complexity or maintenance required to support the system.

How many networking protocols are too many?

Building a connected plant can be an exercise in alphabet soup. There are dozens of protocols that can be used to transfer data between systems. While larger ICS vendors might support most of the protocols, many smaller ones only support a handful. Complicating matters even further, manufacturers of skid equipment often only support one protocol to reduce the complexity of building skids shipped to plants all-around the world.

By focusing on reducing the number of protocols used within a control system, users can reduce the number of different networks that need to be maintained. It also reduces the number of software packages needed to configure and monitor those networks, as well as standardize data addressing to make troubleshooting more efficient.

Although there has been significant progress through the Open Process Automation Forum in standardizing on OPC UA for process control communications, we are many years away from reducing our plants to one protocol. Having only two or three protocols is a realistic goal.

Where to connect the networking protocols

While the connection point on edge devices and skid units are often fixed, controls engineers often have some options where they bring those connection points into the basic process control system (BPCS). While OPC will typically require a Windows-based PC as the interface point, most others can communicate directly with the DCS or PLC system. Most 2- and 4-wire protocols often come in through an interface card in the input-output (I/O) Rack. Many TCP-based protocols can be brought in in multiple ways including directly to the controller, through an interface card or through a dedicated gateway.

When considering where to interface the system, a few key considerations need to be made. Simplicity can be gained by utilizing a dedicated interface gateway which can speak multiple protocols and gather data from various systems, putting them all on the control system backbone. However, this also creates a single point of failure. Perhaps some interfaces need data update rates significantly faster than others. This might require them to be placed on an interface card separate from other protocols to obtain the high-speed data transfer.

A well-designed system will interface in as few places as possible while still providing the redundancy suitable for the application. While bringing communications directly into the PLC or DCS controller reduces complexity, it also puts the control engineer in a position of possibly needing to perform maintenance on something that might not be a critical function on a device responsible for critical functions. It would be very unfortunate if a BPCS controller were to need to be replaced (taking down an entire process unit) to restore communications with an ancillary skid unit. Placing the communications interface point in a dedicated module in the IO rack, or in a standalone communications gateway enables these communication devices to be replaced or rebooted separate from the BPCS logic execution, which adds flexibility to the control engineers troubleshooting and maintenance toolbox.

Some DCS/PLC vendors offer interface controllers, which can speak multiple protocols on several networks at one time. They even can perform minor logic solving so that logic specific to the interface modules can be executed without traversing the network to a BPCS logic solver. When these communications gateway controllers are offered with a redundant setup, they can be an appealing solution to the control systems engineer looking to simplify the network and add maintenance flexibility without sacrificing redundancy.

Alan Polk, P.E., operational technology/cybersecurity leader, Hargrove Controls & Automation. Hargrove Controls & Automation is a certified member of the Control System Integrators Association (CSIA). Edited by Chris Vavra, web content manager, Control Engineering, CFE Media and Technology, cvavra@cfemedia.com.

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Keywords: ethernet, industrial control systems

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