Site Survey Rules for Industrial Wireless Use Case | Automation.com

Site Survey Rules for Industrial Wireless Use Case

June 272014

By Bob Voss, Panduit

Industries are rapidly adopting wireless networks because of their many benefits on the plant floor, including convenience, mobility, reduced cabling and lower labor costs compared to wired networks.

Here are four steps to help plant operators establish wireless zones on the plant floor effectively.

1. The stakeholder conversation
When establishing wireless zones in manufacturing, the first step is to involve all the key players in a conversation about expectations. This discussion could include engineering, production and the IT team. Each stakeholder needs to understand the various reasons behind establishing a wireless network and how the process will work. It’s also a great forum to air future expectations – what each stakeholder expects the wireless deployment will supply to them in the future.

For management, the reason may be to save money on cabling installation. Plant floor staff may want to gain the mobility that comes with the ability to use personal devices throughout the plant. Production might want more flexibility in configuring the manufacturing floor, as new communication products and process improvements are released more frequently. Engineering is able to stay connected while in the plant environment, accessing email and/or VoIP phone assets. They also can access technical documentation from the plant instead of trekking back to the office to retrieve documents.

Wireless installation would be an easier process for the IT team, especially around areas difficult to reach or with moving equipment. All stakeholders could use wireless access to see real-time location of assets, machines and products, as well as KPIs (key performance indicators) around process health and output.

An initial conversation about goals, responsibilities and the process going forward can save time and money down the road, for all involved.

2. Defining the playing field
The next step is to complete a site survey. More variables come into play when the network is not grounded, so a site survey can be even more crucial when installing a wireless network versus a wired one. A wireless network has general connectivity considerations but it’s also important to note that the RF (radio frequency) environment is dynamic in manufacturing plants. It is vital to know the playing field well before planning the wireless deployment.

Because the survey is so important, only someone with network-infrastructure experience, working alongside a person with knowledge of the process, should perform the process. For example, an IT team member may understand networks but not understand mobility needs and assets on the plant floor. The surveyor should look for four main obstacles, to better understand how the wireless zones should be established:

  • Radio-frequency (RF) interference: RF interferes are present in any plant, and the surveyor needs to ensure that no element in the facility itself or in proximity will interfere with the wireless radio waves. He or she needs to consider the location of metal walls or ceilings, as well as any other reflective or absorbent construction elements. Many plant buildings contain a considerable amount of metal, which is all grounded for safety reasons. This can potentially compound interference problems and must be addressed.
  • Parts in motion: Machines and devices on the plant floor are moved and changed out more frequently as production technology advances to meet market trends. Also, wireless communications has the potential to replace and exceed the performance of devices used today like slip rings. Some mobile equipment such as forklifts may require access. The surveyor also needs to consider how plant parts would be moved in an emergency.
  • The dynamic plant floor: If the plant floor is broken out into manufacturing cells, the wireless network should be established so it can respond to changes in equipment placement on the floor.
  • Frequency range: Wireless can be easy to install, but plant operators may be reluctant because of the prospect of conflicting or missing overage. The next step in the site survey is considering the frequency – should wireless be on a 2.4 GHz or 5 GHz frequency range? Especially for mission-critical communications, choosing the right bandwidth is essential. Experts recommend 2.4 GHz for convenient wireless, but 5 GHz should be used for a critical control network. As 2.4 GHz is widely used, it is important to look in a very granular way at which channels in this range have conflicts that could impact network performance.
  • Time: Over a period of time the wireless environment may change through normal operations.  For instance, the 5 GHz frequency range is shared by some radar systems; if you are near a port you could get interference from shipping.  There may be weather radars which are not running permanently.  As you select operating frequencies, make sure that they are stable over a reasonable period of time.

3. Application performance needs
Most application performance needs should have been discussed in the initial stakeholder meeting, but more may arise from site survey. The plant operator should consider the bandwidth and capacity required by the applications, and what is average capacity versus peak usage. He or she should consider latency requirements – how long it takes for a response to be given after a request for service. An application may have higher reliability requirements as well, so the plant operator may consider redundant services for critical business needs.

The use of video for remote maintenance has increased. But high-res video increases the needed capacity for wireless. Even if a facility is not using this video application currently, the plant operator should consider the capacity requirements for future capabilities.

4. Implementing the network
After application needs have been established, several factors must be considered in the implementation stage:

  • Wireless zones, which are physical spaces with common application needs. One zone could be an entire facility, as long as it serves one application. Each zone has one access point or set of access points that serve the physical space, and these points can be set up in different ways. Mission-critical parts can be served with overlapping and redundant access points to ensure connection. Additionally, in network zones, if the facility needs to expand or configure one zone, that can be done from a well-planned zone architecture.  
  • Network environment: An industrial plant floor won’t use the same wireless access points as a residence. Heat, fumes and moving parts can endanger and affect the access points, but those points need to remain reliable. Plant operators must ensure the equipment is appropriate for the environment or encased for protection. The equipment can be a NEMA-type enclosure with antennas mounted internally or externally.
  • When powering the wireless network, two options exist: building power or power over Ethernet (PoE). The power source must be considered before any integration of wireless. Building power can be an expensive installation, with an electrical power feed, conduit and wire. The second option is PoE – one cable to your wireless access point delivering both the network connection and the power to bring the wireless access point to life. PoE has evolved to deliver even more power therefore it’s finding wider applications across enterprises and industrial applications.
  • Future readiness: As network bandwidth can grow rapidly with new applications like video surveillance and mobile device support, plant operators must establish networks that are built ready for the future. Current wire connections may be appropriate for current needs, but plant operators will want to anticipate advances they would want to incorporate in the plant. This may result in upsizing and ensuring network redundancy.
  • Equipment selection: When installing a wireless network, the IT team may want to put in equipment that’s familiar to them, but that equipment may not be rated for the harsher areas in the industrial zone. The wireless team should be educated on the security capabilities of the equipment and develop a security plan. Security features determine who has access to the network and encrypted data. Management should ensure that security is centralized and managed in the wireless equipment, with policies for staff and guest access.
  • Wired infrastructure: Plant operators can easily overlook the requirements for the wired infrastructure connected to the wireless access points. A plant operator cannot be too careful with this consideration. The wired network needs to support the application needs, and have sufficient bandwidth and speed with appropriate latency. As access needs grow, the wired network may require a higher uplink port speeds and higher capability network cabling.
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