On Alaska’s North Slope, 250 miles north of the Arctic Circle in the Prudhoe Bay Oilfield, reality dictates that some control systems find themselves placed close to production equipment in the field. But if those systems aren’t positioned correctly, or properly selected and protected, catastrophic consequences can result.
At the other end of the extreme environment spectrum, such as in hot, humid tropical locations that promote the growth of corrosive organisms on exposed surfaces, similar locating, selecting and protecting of processes must also occur.
Placing controls in extreme environments like these sometimes requires extreme thinking. For example, suppose a petrochemical plant in the bayous of Louisiana determines a need for a new controller that will be located outdoors in the naturally hot, humid environment. The obvious answer is to place the controller in an air-conditioned protective cabinet. But this pathway is not always followed for a variety of reasons, such as when someone up the chain rejects the air-conditioned cabinet request because of its higher operating, maintenance and energy costs.
Considerations of temperature extremes as well as other environmental issues—including vibration, shock, dust, explosive gases, caustic gases, high-pressure hot water, high altitudes, high winds and electromagnetic interference—are all part of the process that goes into purchasing and properly applying modern automation devices.
Though it is best to locate critical control equipment as close as possible to production, basic issues such as air supply to controls and valves must be thoroughly considered, cautions Steve DeVries, senior director of solution architectures at Invensys (www.invensys.com).
Despite the advantages, end users must avoid putting controls too close, cautions DeVries, because part of keeping controls operating well is providing human access. “It’s a big factor, whether underground, offshore on an oil rig, or in a chemical plant where the area is highly dangerous. When someone has to go to those more risky areas, it’s almost like preparing for a space launch—the clothing, oxygen packs, special mask, etc.,” he says. “It takes a whole bunch of time for a person to rehearse and actually do that.”
In keeping with DeVries’ counsel, Dennis Wylie, ControlLogix product manager for Rockwell Automation (www.rockwellautomation.com),advises keeping controls in extreme environments as far away as possible, but as close as necessary to production. If the controls are too close, more expense in equipment and maintenance will be needed to mitigate potential hazards, he says.
>> 3 Steps to Choosing Wisely: Follow this checklist when it comes to using automation technologies in extreme environment applications
Being closer to the production will always be seen as advantageous, however, because it minimizes control cable costs and reduces complexity, adds Richard Duong, Moxa’s (www.moxa.com) business development manager for data acquisition and controls. Whatever the end user’s choice, controls’ proximity to production will be based on the durability those controls exhibit in potentially difficult field situations.
Extreme environment best practices
Ensuring automation asset availability through reliability-centered design is the very best practice, notes DeVries. He points out that the key to successfully achieving and maintaining a reliability-centered engineering and maintenance culture is to employ the failure mode and effective analysis (FMEA) process. FMEA is a step-by-step approach for collecting knowledge about possible points of failure in a design, manufacturing process, product or service. This Six Sigma practice of incident analysis can be used as a daily or weekly measure during operation of the plant and automation systems, DeVries explains.
“Although the severity [of the risk] is not likely to change day to day, the probability can,” DeVries adds. Therefore, teams should be required to watch for any expansion of failure modes or failure trend lines that lead to those failures being categorized as an unacceptable risk, he says.
Planning for worst-case scenarios and informing the team with available documents on what to do in those instances gets Duong’s vote as the most critical best practice. “Technology can work around limitations to some extent, but bad planning and an ill-informed team will ultimately cause operational disasters,” he says.
Warren Johnson of system integrator AE Solutions (www.aesolns.com) also points to safety as the most critical best practice driver. “Define design criteria for the project and then define the constraints before the safety system is built,” he says.
Underscoring the importance of understanding system design to safety, Johnson notes that one of his clients, whose operations are on Alaska’s North Slope, conducts wire-brittleness tests that have resulted in the development of a very detailed specification for the wire used in its control panels.
Never forgetting the purchasing powers-that-be, Corey Morton, director of technology solutions for B&R Industrial Automation (www.br-automation.com), suggests always keeping a cost-vs.-benefits mindset as a best practice. “There will always be hardware,” he says, but as you plan out your extreme environment system, ask yourself: “Am I just creating a technical challenge that will cost money and time without benefit?”
Using a Nexus Tablet 7 as an example, Morton illustrates how inadequate design could reveal technical issues at deeper levels. “When I first got [the tablet], I’d plug it in to charge it, but nothing would happen.” A little research showed the connector inside the unit often came loose as a result of vibration experienced during normal shipping.