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Implementing wireless networks in a manufacturing environment


May 15, 2007
By Hesh Kagan

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Today’s wireless technologies can save a manufacturer big bucks if carefully managed, but there are several constraints that have to be addressed if wireless networks are to be successfully implemented in a manufacturing environment. For one, the technology has to work properly, which is not as straightforward as it might seem. Given that the network and devices communicate with each other over the air at the advertised speed and distance, they also have to work with any number of different vendors’ wireless devices; they have to be reasonably manageable for deployment, modification or configuration; and they must be secure from intrusion and spoofing. They should be tolerant of changes in the radio frequency (RF) environment, including incidental interference and other environmental changes ranging from weather to a passing freight train traversing a line-of-sight communications path.

Another constraint is the fact that there are many wireless standards. The application requirements for distance, bandwidth and power consumption dictate that different standards will be required, but finding what is right for your application is a formidable task. In addition, the technology is rapidly changing. Thus, manufacturers are asking themselves if standards can keep up, and if the rapidly changing technology will make their investment obsolete in two years.

Given all of these constraints, why would anyone be jumping into wireless right now? The primary motivation is the potential savings.

Cost savings
The cost of running wires in an industrial environment is very high, ranging from hundreds to a thousand dollars, or more, per foot. So the cost of incremental measurements for fewer dollars is a big motivator. For example, a chemical company needed to profile the temperature of a steam pipe that ran 2,000 metres across the plant to assure no condensation was developing. The layout of the plant would have required that wires for new temperature transmitters be run underground, which required trenching. This is an old plant and EPA requirements mandate that new construction that requires ground breaking examine the soil for contamination. If contamination is found, remediation is required. Having a wireless transmitter not only reduced the cost of attachment, but avoided any requirement to put a shovel into the ground.

Even bigger savings are available with new applications that could not have been considered in a wired world, including asset performance management and condition monitoring. Most maintenance in a continuous industry follows a break-fix model – wait for something to break and then fix it. This approach is much less expensive than preventive maintenance, because you are not tossing out working parts simply because the instructions call for maintenance at a particular time. The holy grail of maintenance is model-based predictive maintenance. Based on sensors, typically temperature and vibration, a normal profile can be established. As the profile changes or degrades, maintenance can be scheduled for a time that is convenient for the process and maintenance staff. Dramatic savings are being realized with this technology, but it’s only viable with a wireless sensor. If you had to run the wires for all those sensors, the cost would far outweigh the gains.

Wireless management
Wireless networks require significantly more time and attention than wired networks. The key to success is in the management of wireless networks. Today, most wireless networks are allowed to grow in an ad hoc fashion. A good corporate citizen seizes an opportunity, brings in a vendor, and solves a real problem by purchasing a wireless solution. Another point solution is addressed with another vendor, and a third and a fourth, and so on. Each of these solutions has its own technology, its own access point. Each vendor has its own software for security management, and for network and system management. Imagine a half dozen managers coming into work with routers under their arms, setting up subnet groups for their departments. The management information systems and IT folks would be looking on this less than favourably. It simply would not be allowed.

A model needs to be established that, regardless of the state of standards, heterogeneous wireless technologies can be normalized at the access point level (entry into the wired systems). This normalization needs to include a security model that the corporation is comfortable with, and a systems and network management approach that can be managed by plant personnel.

Invensys has adopted an architecture that meets these requirements. The architecture supports a single server in the system as a single point of trust for the security model, and the focal point for common wireless systems and security management. Whenever you are dealing with security architecture, there needs to be a single point of responsibility for policy management, otherwise you are likely to either get contention or non-deterministic behaviour when trying to resolve conflicts in how to handle exceptions. The security server addresses critical functions that must be met for all wireless activities. These security and management functions seem to grow exponentially with the increasing numbers of various devices, networks, communication models and vendors. It’s only by having a common management of the wireless infrastructure that the situation becomes containable. Security and network management functions must include dynamic network management; fault and escalation policy management; configuration management; accounting/usage management; performance management; security management; device commissioning; and a policy service broker.

The policies and standard operating procedures (SOPs) in place for wireless networks must define all methods using, sharing and securing the available bandwidth. This has implications for planning, implementation, operation, maintenance and expansion. For these reasons, wireless networks require a very thoughtful level of construction.

Policy management and validation also ties into the end-user’s existing IT requirements. The system must be designed to comply with corporate requirements for activities like reporting errors, and observing network behaviours and performance based on that information. It must cover every aspect of the operations, from initial configuration to ongoing optimization.

Commissioning and qualification of the wireless network is comparable to commissioning and qualification of any network, but with added emphasis on security and interference. Interference would be addressed first during an RF site survey, which uses scientific tests to measure RF in the plant and in the local area surrounding the plant. Additional security and RF interference testing must also be built into routine maintenance procedures to account for changing internal and external conditions.

Performance, availability and utilization are also reporting criteria within systems management, and must be considered as part of an ongoing management program. Policies, such as alarm/alert handling, are part of the system’s management function.

Policies and SOPs that meet regulatory requirements must also be in place for handling problems. Once the system detects interference, for example, what does it do? Will it reroute traffic, change frequencies or reconfigure antennas to be active or inactive? Some of the options depend on the capabilities of the technology, but within that framework, policy is necessary to guide choices.

Implementation
Implementing a management infrastructure requires several months of cross-company planning. Implementation of the technology itself can usually be done in a few weeks. Few companies have the resources to maintain staff necessary for initial implementation, especially because demand for specialists with relevant skills is very high. Outsourcing to one of the emerging specialist firms is currently the most cost-effective strategy for companies that want to enjoy the benefits of wireless networking immediately with little risk.

The following checklist can be used to assess your wireless needs and design a system that is consistent with your wireless strategy, policies and quality requirements:

  • Survey the entire company to determine where wireless technologies can best support your business strategy;
  • Create an enterprise-wide policy to control wireless deployment;
  • Design an architecture that will achieve these goals effectively;
  • Conduct an RF site survey to identify potential sources of RF interference and locate wireless communications devices, both internally and external to the plant;
  • Select and purchase hardware and software that is cost-effective, proven and scalable;
  • Develop a prototype in an area with high ROI potential for immediate payback;
  • Integrate to the existing business and operations systems;
  • Measure and evaluate ROI effectiveness of application;
  • Collect lessons learned, measure cost effectiveness of improvements, reassess the strategy, and plan next steps, including additional sites and plants, and global solutions for a rollout; and
  • Conduct ongoing monitoring, maintenance, support and optimization services, and incorporate relevant technologies as they emerge.

Wireless is here to stay. The technology is capable of enabling many valuable applications across the enterprise. The key to a safe, secure and robust implementation of wireless networks is enterprise-wide planning, co-ordination and management.

Hesh Kagan is the director of technology in the Applications, Services and Solutions division of Invensys Process Systems. He is currently co-ordinating the wireless strategy and product development for the Invensys group. Kagan is a founding member and the current president of the Wireless Industrial Networking Alliance (WINA), an organization focused on increasing the adoption of wireless technologies in industry.