Novel field shelters incorporating liquid cooling protect vital refinery process controllers
Outdoor shelters with a novel combination of Intertec's passive and active cooling technologies have been chosen to protect vital control systems at a Middle Eastern refinery.
The environmental protection solution is being provided as part of an upgrade to the burner management systems at the core of the plant's refining processes.
High-reliability PLC-based systems will provide the control and safety functions needed for management of eight separate burners.
However, the physical location of the systems – deep inside the process – and the harsh coastal desert location of the refinery, pose major additional challenges for this engineering upgrade.
The project partners selected the field instrumentation protection specialist Intertec to provide the enclosure solution for its novel protection ideas that are set to enhance the overall functional reliability of the control systems.
Intertec's design features custom-designed remote instrument enclosures (RIEs) based on composite GRP materials that protect against the many environmental challenges of the application, including very high levels of UV, extremes of temperature, dust, and sand abrasion.
The technology includes a regulated internal environment that provides the essential cooling required for the reliable operation of the electronics in the harsh Middle Eastern climate.
The IP65-rated shelter also utilises the plant's instrument air service after drying and filtering, which provides a slight positive pressurisation of shelter interior atmosphere for safe operation in a hazardous area, as well as ensuring there are no corrosive chemicals in the atmosphere.
"Control and instrumentation systems are being sited much closer to the process, deep inside corrosive and hazardous areas - and this in turn is demanding higher levels of reliability. GRP enclosure construction materials, combined with innovation in the associated protection systems such as cooling, are helping engineering consultancies to create advanced new plant solutions," said Keith Wood, Intertec's project manager.
The Intertec system features three cooling technologies, namely an air cooler, a water cooler, and a water-based passive cooling system.
In normal operation, the water cooler and passive cooler operate in combination to decrease the internal operating temperature of the eight shelters.
The aluminium heatsinks of the PLCs and cases will be installed directly onto conductive mounting plates, in contact with the liquid-based cooling media, which provides a much more efficient cooling mechanism in addition to conventional air convection.
The passive cooling system works by exploiting the regional climate's large temperature swing over the daily cycle, using water as a medium to store the coolness of the night and moderate internal temperatures during the day.
Intertec's addition of an electrically powered water cooler improves efficiency and reduces the size of the water tank needed for the passive cooling circuit.
If the powered water cooler should fail, the electrically powered air cooler switches on to maintain the internal environment, and if both of the powered water and air coolers fail, the passive system can maintain a low shelter temperature for several days.
The Intertec shelters are scaled to accommodate the PLC control and safety systems, but are also designed to be accessed only from the outside in normal plant operation.
The powered water and air cooler units are mounted on an external wall and several other small panel-mounting enclosures provide external access to the electrical connection and I/O termination points.
The PLC is fitted with a touchscreen HMI panel that sits on an external wall, allowing operators on the ground to make adjustments to the control programs locally if needed.
All eight shelters use a common design with a footprint of around 2x3m, plus a heat exchanger on the roof, which also overhangs to provide shade.
The shelters will be assembled and factory tested at Intertec's European manufacturing centre in southern Germany.
Delivery of the eight RIEs will start in the second quarter of 2017.