Classified as hazardous areas, offshore oil rigs require that any equipment installed on them is designed and certified accordingly – including electric motors to drive critical gas compressors.
Foster Yeboah, Zest WEG’s regional sales manager for the West African Region, says that WEG electric motors for these applications comply with IEC standards and associated hazardous area specifications, which certify equipment for use in ‘explosive atmospheres’. Considering the hazardous marine environment, all the WEG machines were supplied with tough epoxy paint and conformed to an IP65 rating.
Six large WEG motors are being installed on an oil platform off the coast of Ghana, over a staggered schedule from late 2020 through 2022.
Four of the new motors are large 9,500 kW, WEG MGW800 machines, and two are 7,000 kW MGW710 machines. With weights of up to 23 tonnes, these electric motors exceeded the 19 tonne weight limit of the oil platform’s crane which meant that the motors were shipped to site in component form, for assembly on site.
“Despite Covid-19 disruptions and challenging logistical conditions, Zest WEG is successfully supplying, testing and installing these motors for the customer,” says Yeboah. “These six WEG motors are upgrades of previously installed WEG motors, which have been operating successfully on this site for over a decade.”
“Of course, the Factory Acceptance Test (FAT) is always vital, so this has to be conducted on all the motors after they are manufactured and tested,” he said. “Covid-19 initially made it impossible for the client to be physically present at the factory in Brazil, so some tests were witnessed virtually.”
To deal with the weight restriction of the crane on site, the electric motors then had to be dismantled in the factory before shipping, he explains. Rather than being shipped as a single unit – as is normally done – the motors were carefully packaged into component form. Particular care had to be taken with protecting the rotor during shipment.
“The rotor is a critical item, and it is crucial that great care is taken when transporting this item,” he says. “The packages are then shipped and stored at the customer’s warehouse in Ghana, before being taken to the offshore oil rig.”
Zest WEG technicians assemble the electric motors on the oil platform, including the various electrical and hydraulic connections and piping. Commissioning and testing are done before the system goes online. The first of the six installations had to be done when Covid-19 restrictions required quarantining periods – adding to the complexity of planning.
The large WEG motors in this application are cooled using the IC81W air-water cooling principle, says Yeboah. Air is circulated through the motor base where the rotor and stator generate the most heat. A heat exchanger then extracts the heat from the internal circuit air flowing through it.