The IICA's Technical Evening in Sydney last month focused on plant-wide wireless with three speakers looking at the risk versus rewards of implementing wireless technology.
The session was opened by Kevin Gomez, Editor, PACE magazine. He compared the emergence of wireless to the step change that occurred when the industry moved from analogue to digital.
He touched upon some of the key factors holding back the spread of wireless which include security risks, competing standards, and dependence on battery power. Kevin also pointed to the results of a recent survey where 86 per cent of the respondents said: "We're not sure how to implement wireless".
Simon Lillie, Product Specialist – Field Instruments, Yokogawa Australia, highlighted the technology advances that minimise the perceived risks. An important "fear factor" is signal interference; however the technology has evolved to overcome these issues.
Channel blacklist can automatically avoid congested channels. Another technique is frequency/channel hopping which minimises the strain on any one channel by spreading the signal over the entire available band.
The third method in addressing this issue is DSSS (Direct Sequence Spread Spectrum) where the energy is spread so the signal looks like noise to other systems.
Simon also laid to rest the fears regarding battery life. With moderate update rates for a wireless instrument, battery life can extend up to ten years. Moreover the battery is easily replaceable and may even be used in hazardous locations.
With no signal or power wiring, wireless brings numerous advantages. Simon highlighted the key ones: Implementation in hard-to wire sites can reduce costs and improve safety; and modernisation of existing facilities with wireless leads to fewer personnel on site.
He was of the view that the existence of two standards, ISA100 and WirelessHart, need not be a limiting factor for customers and that benefits can be gained by adopting either. The key consideration is to implement wireless technology and derive the benefits that follow.
Endress+Hauser's Jonathan Soanes brought along a few wireless instruments to demonstrate their capabilities and features. He stressed that there are some risks in employing industrial wireless but the rewards outweigh the risks.
Shalveen Sharma, Pre-sales Application Engineer, Siemens, offered an interesting perspective on wireless LAN and highlighted the benefits including mobile diagnostics, Failsafe SIL3 approval and reduced maintenance costs.
He then went on to dissect a wireless application that faced numerous communication issues before the team from Siemens came in and rectified the problems. The site was an aggregate ship loader with the hopper communicating to the four access points (APs) across the conveyor belt.
The site was experiencing 40 to 50 dropouts per day. The team discovered that there was no channel planning and all the APs were communicating on the same frequency causing interference. The frequency channels were then reorganised and correctly laid out to avoid overlap.
Subsequent tests using SINEMA E software indicated excellent signal strength with signal quality showing remarkable improvement (90 to 100%). However, the communication problems persisted.
The team then turned their attention to the antenna and discovered that it was mounted at an incorrect height and too close to the wall. The antenna was correctly set up and the application has been running trouble free since 2010. Shalveen's message is 'plan for wireless to ensure success'.
The session was chaired by Chris Hoey, Managing Director, Burkert Fluid Control Systems.
Julie Meynell is Sydney Branch Secretary, Institute of Instrumentation, Control & Automation Australia (IICA).