Planning Your Wireless Instrument Installation

You may have seen quite a bit of news coverage (here, here) on wireless technology as it applies to plant instrumentation. At the recent Emerson Exchange, Emerson also announced some wireless news.

If you are an automation engineer, you might have thought about some applications where you would like to try this technology.

Your best course is to start with a simple business case. Perhaps the operators perform rounds to get readings from gauges and instruments not connected to the automation system. Having this information and associated diagnostics coming from wireless devices could possibly make your plant’s instrument technicians more efficient.

I caught up with Mark Sagstetter in Emerson’s Rosemount Measurement business. He recently went to a refinery along with John Biscone, a service technician in Emerson’s Instrument & Valve Services business. Operator and instrument technician efficiency was the very business case this refinery was pursuing. Mark and John were contracted to provide their expertise to help plan the network and installation process of the wireless instruments and gateways. Much like the early days of digital bus technologies, this expertise can help automation engineers establish best practices for planning and executing future wireless installations.

In the course of a two-day site visit, they worked with the plant engineers and identified five process units including four tank farm locations that met the criteria for increasing operator and instrument technician efficiency.

My understanding when talking with Mark is that there are basically two overall best practices to follow when implementing a wireless field network. The first is planning the wireless network and the second one is the network installation.

When executing the best practice of planning the Self-Organizing wireless networks, Mark and John like to have scaled site drawings. Unfortunately, in this case, scaled drawings were not readily available. Necessity being the mother of invention prompted the team’s great idea to use Google Earth to generate site maps. They used the printouts during the walk-through of these process units to help envision device locations, gateway locations, plot anticipated communications, and to help identify possible impenetrable situations.

As part of the best practice of planning the network, it is a good idea to plot at least two paths of anticipated good communications for each instrument. Using a color-coding scheme, with one color to mark anticipated good communications paths and another color to mark potentially interrupted paths of communication, John and Mark were able to use this process to help understand how the network may function when installed. It also helped to understand, plan for, and possibly eliminate possible pinch points and/or possible impenetrable situations before the actual installation.

With every Self-Organizing wireless instrument being capable of being a router (sending and receiving messages from other instruments), possible pinch points and impenetrables are easily overcome. This is accomplished with the addition of measured points or instruments that act as routers or range extenders.

During the installation-planning portion of the site visit, Mark and John recommended the plant engineers follow the wireless installation best practices. To do this, the plant engineers would need to power and commission the gateway first. Then install, power, and commission the instruments, starting with the instrument closest to the gateway and continue working outward from the gateway. The instruments’ connectivity to the gateway should be verified each time after installing, powering and commissioning the instrument.

One thing I noted in my conversation with Mark is that the instruments mount with standard process connections. Engineers have been using these standard connections for years. The actual mounting location for the instruments and gateways were determined by providing a forearm’s length (a measurement device every instrument technician has with them at all times) of space between the antennas and any wall or metal structures to avoid signal attenuation.

Installation would continue by powering, installing, and commissioning instruments outward from the gateway, until all the devices have been brought on-line. By installing the instruments in this fashion, the actual formation and connectivity of the wireless Self-Organizing network can be compared with what was expected during the best practice of planning the network.

Beyond the immediate need to help the plant engineers plan a smooth installation at this refinery, Mark and John helped them establish best practices to aid in future wireless projects/installations.

Posted Thursday, October 25th, 2007 under Measurement, Project Services, Wireless.