Wireless for operations: proprietary versus standards; adopters versus laggards
Wireless networks using current methods and protocols have been part of the process industry for more than a decade. There are many reasons why facilities adopt wireless networks, but they often boil down to two categories.
The first category is reactive; wireless is used to bolster saturated wired infrastructure or in locations hard to access with cable. The second category is proactive; wireless is a critical means to quickly increase the reach of instrumentation and communication capabilities without the costs, long installation time, and possible downtime required for wired instruments.
Regardless of the category, the ultimate goal is to increase a facility’s productivity and the workforce’s effectiveness. There is a constant drive for profitability despite there being less experienced personnel in the industry and reduced worker populations overall.
Today’s networking protocols fulfill four requirements for success:
- Reliable communication
- Secure data transfer
- Deterministic communications
- Managed power consumption.
Wi-Fi and other onsite networks
When most people think of wireless, their first thought is the wireless Ethernet (Wi-Fi) networks that connect computers, phones, tablets and other devices to office, home and even industrial networks. While Wi-Fi is very versatile and good for a wide variety of applications, its high-power requirements and high-protocol overheads make it impractical for measurement devices where battery life needs to be measured in years. Still, the ubiquity of Wi-Fi-enabled devices and the high bandwidth it offers make it suitable for wireless plant networks (WPNs), Figure 1) used for other purposes.
The most common uses for Wi-Fi include mobile-worker applications, remote video monitoring for safety and security, and similar applications. When considering a WPN, it is important to understand the typical process plant environment is not as conducive to communication as a home or office. The higher density of metal, multiple sources of electromagnetic noise, and the wide range of ambient conditions in industrial environments often calls for a higher density of access points in the facility or plant, particularly around potential noise sources.
In most cases, WPN implementations should not be left solely to the company’s information technology (IT) team. Installers who are used to working in office environments don’t always understand the problems of working in a process plant. The network may perform inconsistently, resulting in a loss of trust in the WPN by the users. When designing a WPN, it is best to engage vendors who have experience in industrial automation and understand the design requirements for installing Wi-Fi in industrial plant settings.
Alternatives to Wi-Fi for WPNs and broader geographic networks, such as a municipal water or electric utility applications, include long-term evolution (LTE) and wireless interoperability microwave access (WiMax). These networks offer different ways of handling coverage distance, bandwidth, mobility, and network support. In some cases, deployments may involve the participation of a commercial network provider, or may be installed and maintained privately. LTE and WiMAX are appropriate for a variety of use cases, but are not suited to process instrumentation networks.
Another commercial protocol with that can be applied in an industrial setting is Bluetooth, and its later incarnation Bluetooth Low Energy. Bluetooth was originally designed as a cable replacement technology for short-distance, point-to-point connections such as wireless computer keyboards, cellular phone headsets, and headphones. Industrial adaptations include interfacing a laptop computer to a programmable logic controller (PLC) for configuration and maintenance functions without a physical cable, and other similar short distance applications.
Wireless instrumentation networks
One of the positive factors supporting user acceptance has been the establishment of standard protocols for wireless field instrumentation networks. The two main standards governing wireless process instruments: International Society of Automation’s (ISA’s) 100.11a-Wireless systems for industrial automation: Process control and related applications and WirelessHART, each adopted as international standards IEC 62734-Industrial networks – Wireless communication network and communication profiles and IEC 62591-Industrial Networks-Wireless communication network and communication profiles-WirelessHART, respectively. While these standards cover much of the same material, there are significant differences in their approaches. Both have established a reputation among vendors and users.
The first of these to hit the market was WirelessHART. The first WirelessHART field devices were released in 2007. To overcome the interference issues inherent in industrial applications, WirelessHART uses a mesh network (Figure 2) where each device acts as a repeater for the network, providing multiple paths for signals to reach the access point or gateway. Since it was designed specifically for industrial applications by the FieldComm Group, certified devices from any manufacturer can interact with each other. Additionally, bandwidth use and security considerations are optimized for measurement and control applications. As wireless instruments are frequently battery-powered, the protocol was designed to minimize power usage. Depending on how frequently a given device provides measurement updates to the host, battery life can be up to 10 years.
Developing the ISA100.11a standard was a longer-term project and was not completed until 2009. It is part of the larger ISA100 family, which covers a wider range of wireless applications. ISA100.11a is specifically for wireless instrumentation. It takes a different approach regarding how devices mesh, requiring users to determine how they interact. This necessitates a higher degree of network management than WirelessHART requires, which is self-organizing.
ISA100.11a is generally installed so field devices directly communicate with one or more access points, which then communicate to a wireless gateway device that schedules communications and forwards the data to the host system. ISA100.11a devices can also be configured to act in a mesh network when it is necessary to improve signal reliability, but this reduces battery life.
In some applications, various low-power wide-area networks (LPWANs) have been used to varying degrees of success. The original application of these protocols was for very low-bandwidth communications over very large areas, such as smart power meters for electrical and gas distribution companies where individual customer meters typically send updates once a day. While they have an extremely long range, the very low bandwidth and slow update times of these protocols make them unsuitable for most industrial monitoring applications.
Adopters versus laggards
According to Everett Roger’s Diffusion of Innovations, the adoption of new technologies can be described with a curve from innovators and early adopters who are excited to experiment and try out a new technology, through to laggards who come very late to the party (Figure 3). Engineers who installed the first WirelessHART and ISA 100.11a devices in the 2007 to 2010 period would have fit the innovators’ description. Large instrumentation vendors investing heavily in developing devices using WirelessHART and ISA100.11a supported the successes of those innovators and early adopters.
Where a WPN operated in conjunction with a wireless instrumentation network, plant personnel quickly realized many advantages (Figure 4). For example, giving plant personnel access to the control system data with mobile worker applications in the field can reduce loop commissioning time by up to 50% by enabling increased efficiency for operator and engineering workflow. Other applications such as location monitoring can significantly improve mustering during an incident, and wireless cameras provide significant safety and operational benefits.
Looking at the current state of the wireless instrument market, WirelessHART is now entering the stage of the early majority. Most large industrial customers in the oil & gas, petrochemical, power, and other process industry markets have installed WirelessHART networks.
Extending the range of instrumentation
The first generation of wireless instrumentation was all about process variables, but users quickly realized the additional data provided could enable asset condition monitoring and other applications. For example, adding a WirelessHART-enabled acoustic sensor can determine if a steam trap is wasting energy, or if a pressure-relief valve is leaking. The same concept can be extended to all sorts of diagnostic applications now because of WirelessHART networks’ capabilities.
While saving the cost of wiring is still a major benefit, the greatest value of wireless instrumentation and networks is the ability to facilitate pervasive sensing systems. With the costs of end devices and networks declining, the ability for plant operators to gather data and support decision-making has increased with many different applications.
Shane Hale is the director of global business development at Emerson Automation Solutions. Hale has over 27 years of experience in the instrumentation and control field in many industry segments. He joined Emerson 20 years ago as a field technician in Sydney, Australia, and has held various roles including project design and commissioning engineer for international projects, business development manager, director of product management, and now global business development for Rosemount – wireless. Shane has been involved with several standards committee boards including the AGA Gas Measurement Committee and the ISO Standards working groups. Edited by Emily Guenther, associate content manager, Control Engineering, CFE Media, firstname.lastname@example.org.
KEYWORDS: Wireless plant network (WPN), WirelessHART
- Wireless plant network design and management
- The value of wireless instrumentation
- Protocols to use for WPNs.
If you’re still waiting for wireless, are you losing productivity?