Wireless technology increases efficiency and safety in a chemical refinery.
Using wireless technology for monitoring the measuring points in industrial plants has become an attractive choice for plant managers. Today, the plant manager is able to build a quick and cost-effective network solution to enable flexible information acquisition and to improve maintenance efficiency and safety.
To enhance reliability and safety, wireless temperature transmitters and wireless pressure transmitters were installed to monitor temperature and pressure measuring points in a large chemical refinery. These replaced the existing offline pressure and temperature gauges that required manual reading.
The wireless technology used for this project is based on ISA100.11a Standard—the Wireless Technology for Process Automation that was ratified in 2009 by the ISA100 Wireless Systems for Automation standardization group. This group is one of the subdivisions under the International Society of Automation (ISA).
Existing Challenges
Traditionally, many refineries still manually collect or read data from different measuring points throughout the plant to monitor and maintain plant operation. This is due to the high cost of installing wired instrument networks.
This article discusses a real-world example involving a large chemical refinery. The refinery covers a huge area. Cabling between each wired transmitter is approximately 300 meters. Wiring the entire refinery to monitor the measuring points spread throughout the refinery is not affordable. Therefore, many of the pressure and temperature measurements are monitored off-line.
A human patrol must physically visit the refinery everyday and manually read the pressure measurements from traditional pressure gauges and the temperature measurements from traditional temperature gauges. Then the person responsible for patrolling the gauges must report the readings to the control center via phone. After which, the operator enters the reported data into the system.
This manual reading, reporting and entering process was necessary to record the day-to-day operation of the refinery. The refinery searched for a way to automate this process with the goal of eliminating human errors in reading and recording each measurement, enhancing operations in real-time remote monitory and improving overall safety. The plant manager looked for a cost-effective and reliable network solution allowed for continuous, online reading of the pressure and temperature measurements and expanded its networking capability in the future for more measuring points and other measuring values.
ISA100.11a Wireless Technologies
The use of wireless technologies for a particular monitoring application and to solve a particular problem in the refinery has existed for a decade. Eliminating cabling and lowering the cost of installation is the biggest advantage of wireless technology.
However, wireless technology has still not been widely adapted or deployed in the industrial environment. One of the key reasons is the lack of options designed for plant-wide industrial applications. Plant managers have not wanted to deploy a solution that could become obsolete. ISA100.11a is the wireless standard for industry automation and is able to balance five of most important aspects of the industry requirements. These requirements are:
Reliability—The product should provide better than reasonable security and have robust methods for wireless communication and redundancy.
Scalability—It must have a single network infrastructure with a common network management and security management function. The network supports from a few to a ten thousands of sensors in the field, is capable of supporting short and long radio ranges, can coexist with other wireless technologies within the same frequency band and effectively transports small sensor data along with large data throughput (such as waveforms or firmware updates).
Openness—The solution's interoperability is well defined in its communication interface, allowing users to pick the best-in-class product in the market with global usability and leverage existing well-approved communication models and protocols such as IPv6, UDP and 6LowPAN.
Easy deployment—The solution should allow for easy installation, single management function, simple maintenance and power management. It should also support over-the-air provisioning for easy firmware upgrades, maintenance and operation.
Multifunction—Multiple application protocols within a single wireless infrastructure such as HART, Foundation Fieldbus, Profibus and Modbus should be supported, allowing easy integration with legacy systems. Also, it must be able to support restricted latency and flexible timeslot to accommodate different application requirements and be designed to handle from Class 1 for monitoring to Class 5 for close loop-control.
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Figure 1. The wireless configuration of the pressure and temperature monitoring project in a chemical refinery.
ISA100.11a wireless technology for process automation is designed to address all these requirements. It is a user-driven wireless industry standard to enable a cost-effective network that supports everything from monitoring to simple control.
ISA100.11a is an ideal wireless communication choice for industrial applications because it was designed with a self-organizing and self-healing capability. A flexible mesh and/or star network topology ensures flexibility and optimizes power consumption and ensures communication reliability. Wireless radio technology changes with time. It requires that the wireless network decouple its network layer from the physical media to be flexible, adapting to the new radio technology.
The ISA100.11a wireless standard has been designed with this concept in mind. With a single wireless network infrastructure, a new ISA100.11a product handles multifunctional sub-networks using the backbone infrastructure, which can support a large amount of sensor deployments. Additionally, it is easy to accommodate a variety of sensors for the plant's needs and integrates into an existing, wired network infrastructure.
Field Wireless Solution
Based on the many wireless considerations, a large refinery covering a big geographical area selected an ISA100.11a wireless solution for a field test. The objective was to remotely monitor the pressures and temperatures from multiple measuring points. In the existing system, the pressure and thermal gauges were off-line with no control center communication, requiring human patrol.
At the initial field test, eight transmitters were used. Two repeaters were used to cover four transmitters at each side of the refinery. Each repeater was installed in a tower which was more than 40 meters high to avoid large obstacles. The repeaters communicate online with the gateway. One gateway was installed on the roof of the control room. The distance between the gateway and transmitter was approximated 300 meters.
Figure 1 illustrates the wireless configuration of this project, which monitored pressure and temperature. The result has been a high quality and robust wireless communication that has achieved the initial goals of the project.
Conclusion
The ISA100.11a standard-based wireless network eliminated the restriction of traditional pressure and thermal gauges, and replaced it with a real-time, remote monitoring system using ISA100.11a-based wireless pressure and temperature transmitters. The wireless technology has increased day-to-day operation efficiency, limited human errors and the monitoring of the plant in real time and enhanced plant safety by automating the monitoring and reading process.