Wireless Convenience In The Process Industry

Selin Yılmaz discusses how the use of wireless technology has developed and changed over the years, focussing on some of the standards and technologies.

Connection, companionship, and compatibility are words that describe relational co-existence between two or more objects, ‘things’, nodes, or beings. Initially present in the natural world between plants, animals, and humans, relational co-existence first extended into the technology domain in 1876 with the physical hard-wiring of the early telephone. Since the development of the first telephone, hard-wired networks have evolved to be based on optical fiber, then coaxial-based Ethernet and broadband, among others.

The shift from hard-wired to wireless in professional and commercial environments started to become reality in the 1970s and 1980s. Since then, wireless applications in personal consumer and industrial environments can largely be attributed to the pursuit of ‘convenience’. The convenience delivered by wireless networks in the process industries includes improved flexibility, scalability, less cabling, quicker network installation and commissioning, incremental production, and reduced maintenance costs. These benefits have been mostly seen in monitoring and controlling multi-loop processes.

Wireless networks

A wireless sensor network consists of distributed autonomous sensor devices that converge together to undertake monitoring of physical parameters such as temperatures, flow, pressure, and vibration levels. A wireless field instrument will comprise a conventional wired equivalent, except with a sensor or actuator connected to a radio transmitter or antenna and powered by a battery.

The wireless sensor or actuator properties are similar to those used in wired instruments and have similar characteristics. The wireless sensor network system components communicate relationally through signals emitted within a defined frequency band by the radio transmitter or antenna. For typical wireless sensor networks, the key system components include sensors, routers, and a wireless gateway. Routers can also have the capability to sense designated signals, while the wireless gateway is also referred to as network administrator and has a connection that is wired to the backbone automated system.

A key challenge with industrial wireless sensor networks involves the use of low-power microcontrollers, limited network compute processing power, and limited battery life, whilst needing to maintain high reliability and up-time of communication protocols over time.

Automation of industrial processes typically entails two networks – namely the field network and the control network. However, such networks vary according to the different designs and expected plant operating strategies. Currently, industrial wireless sensor networks fall within the field network classification, although classification boundaries are becoming less clear with the incorporation of wireless technology into industrial control networks, standardizing around generic automation networks. This has involved the migration of substantive parts of conventional wired industrial process networks to wireless technology.

Furthermore, recent innovations arising out of industry standardization efforts, such as Open Process Automation Standard (O-PAS) and Module Type Packages (MTP) are resulting in further integration.

Standards and technologies

A working group of the Institute of Electrical and Electronics Engineers (IEEE) specifies the Wireless Specialty Networks standards. IEEE standard 802.15.4 for the low-rate wireless personal area network is the enabling technology for many applications within the wireless sensor network field. This standard describes the physical layer (PHY) as well as the medium accessibility controlling sublayer (MAC) for low-rate personal area networks. The physical layer types include three 868/915 MHz bands and one 2.4 GHz band.

This standard is the basis for several wireless standards of which WirelessHART and ISA100.11a are used in the process industry.

WirelessHART is based on the 2.4 GHz IEEE Std. 802.15.4 physical layer (PHY), and combines TDMA (time division multiple access), as well as FDMA (frequency-division multiple access) methods of access. It offers reliable wireless multi-hop communication for process applications.

This is made possible through full mesh network topology as well as self-configured mechanisms and self-healing mechanisms. The HART command is the application in which the network messages are transmitted for WireslessHART. These are bound to the HART protocol based on the respective layer applications.

A major component of the WirelessHART standard is the gateway which is capable of sending and receiving data from a field device. The gateway is a network device that consists of at least one interface, such as serial or Ethernet, to connect to an engineering or monitoring station or operator workplace. Such gateway-type devices use function as access points for connecting the wireless sensor network (WSN) to the process automation network. The sensors and or devices which connect to plant processes, characterize or provide control of the process and produce and consume wireless packets in the industrial wireless sensor network (IWSN).

In the case of WirelessHART, another handheld device component is applied for out-of-band communications to provide encryption keys to sensors or device distribution. For ensuring security, the WirelessHART standard has stated encryption security keys which are used for ensuring confidentiality as well as integrity both in networks and at the media access control (MAC) level. The security keys include universal keys, join keys, network keys, as well as session keys.

Another standard for wireless instrumentation is ISA100.11a; initiated by the International Society of Automation (ISA) standards committee to provide robust, secure wireless communication. The standard is also based on the 2.4GHz IEEE Std.802.15.4 physical layer and employs a combination of time-division multiple access (TDMA), as well as frequency division multiple access (FDMA) methods of medium access for wireless communication. ISA100.11a also has the capability to support real-time Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA) mechanisms.

As per the wireless instrumentation application demands, ISA100.11a has a tunneling protocol capability due to its object-oriented application.

A Future with IoT

One of the key objectives of the O-PAS and MTP standards is the reduction of vendor lock-in, where third-party assets cannot be incorporated into a network architecture. Despite open protocols, some HART solutions are not compatible with others. This has led to the development of IoT-based, open protocol technologies such as LoRaWAN to forge multi-node low power, wide area wireless network monitoring capability.

Use case applications of IoT-based wireless networking technologies such as LoRaWAN are extensive.

In 2018, for example, as part of an IoT strategy to stabilize production and maximize efficiency throughout a biochemical plant producing amino acids, additional monitoring of pumps, fans, centrifuges, and stirrers was needed. Approximately 100 Yokogawa Sushi Sensors, based on LoRaWAN technology, were installed on critical production equipment to measure temperature and vibration. Vibration and temperature values measured periodically with these sensors are stored in the cloud. Depending on the device, the data acquisition cycle is set to 10 or 30 minutes.

Another example of the deployment of LoRaWAN technology is in the sewage and wastewater industry. This has involved wide area monitoring of multiple nodes within chemical parks, communities, and suburbs for pollution control, compliance, and maintenance purposes. LoRaWAN-based technologies such as the Yokogawa SENCOM SMART Sensor Platform have been deployed in many instances to provide insights into pH, conductivity, and Oxidation Reduction Potential (ORP).

Selin Yılmaz is Product Manager - Field Instruments - Industrial Automation Marketing at Yokogawa Europe B.V.