Oil & gas
reason, a cost benefit analysis should be completed prior to rewinding to determine if purchasing a higher efficiency motor is economically advantageous. Hazardous area motors are now available with high efficiency ratings to IE3 or IE4. Because energy consumption accounts for 96 per cent of the total life cycle cost of a motor, paying extra for a premium efficiency motor will result in return on investment over its lifespan. The recent introduction of stricter ecodesign requirements (EU 2019/1781) for electric motors has accelerated this trend. Until 2021, some motors, including those designed for hazardous areas, were exempt from energy efficiency regulations. This is no longer the case under the current regulations. Additionally, these regulations also now apply to variable speed drives (VSDs). The legislative changes have impacted many industries, but sectors with high energy usage or using ATEX motors, such as the oil and gas industry, have seen the greatest transformation. The new regulations replaced the regulation EC 640/2009 and have brought reductions in energy consumption related to motor use, while maintaining the required level of safety. It is estimated that by 2030, this will deliver extra energy savings of 10 TWh/yr and GHG emission reduction of 3 Mt CO2 equivalent annually.
MOTOR SIZING Significant improvement to motor design can be achieved, without substantially increased costs. However, the electric motor must always be properly dimensioned according to its real load. If a motor is oversized, with the actual load less than 50 per cent of the rated load, it will reduce efficiency and power factor values. For this reason, it’s important that efficiency and sizing considerations go hand in hand. There may also be additional factors to bear in mind when choosing ATEX motors for oil and gas applications. As a result of safety requirements, explosion proof motors (Ex db, Ex dc) may face design constraints such as derating for VSD operation or reduced starting current.
This may result in a larger frame size and additional considerations when retrofitting equipment with a need for motor interchangeability.
INSTALLING A VSD OR SOFT STARTER Although very few oil and gas applications require 100 per cent flow continuously, many of the motors employed in these applications, such as pumping systems, are started at full speed and remain at full, fixed speed while in use. VSDs can effectively control rotating equipment and offer the best efficiency advantages in variable torque applications. In fact, according to the European Committee of Manufacturers of Electrical Machines and Power Electronics (CEMEP) a 20 per cent reduction in speed could lead to a 50 per cent reduction in energy. To deliver the maximum energy saving potential, VSDs must be commissioned and installed correctly. This is where partnering with an expert like WEG really pays off. If the VSD has not been properly configured this can impact the performance of the system. To maximise VSD reliability start by considering the application conditions and the required speed. Parameters usually have a ‘default’ setting which will probably be adequate for most applications. However, these should be checked and adjusted for optimum operation. Motors are often left to idle, which uses
energy unnecessarily. This is where soft starters should be considered. As the name suggests, soft starters allow the motor to start the load more gradually by limiting the voltage to the motor and providing a reduced torque. In addition to reducing energy consumption, a reduced voltage soft starter helps protect the motor and connected equipment from damage by controlling the terminal voltage.
DIGITALISATION AND MOTOR PERFORMANCE SENSORS Correctly implemented data analytics systems and tools can overcome the operational complexity of oil and gas operations. By combining advanced engineering, the latest data science and computing power, there is potential to make improvements across the board. Instead of replacing conventional methods of operation, digitalisation will supplement them. For example, to keep motors running optimally in oil and gas plants, managers can install retrofit sensors. With important metrics monitored in real-time, built-in predictive maintenance analytics will identify future problems, preventing shutdown and potential safety concerns.
CORRECT MAINTENANCE PRACTICES
Regular maintenance should be carried out on the entire motor system. Performance will naturally decrease after prolonged heavy-duty use or the exposure to harsh conditions. Engineers should opt for products that can provide energy efficient operation in harsh oil and gas environments. Like many energy-intensive industries, the oil and gas sector is exploring new solutions to increase production and energy efficiency. As the sector continues to evolve, it will continue to rely on high efficiency technology as a reliable pillar in the wider energy efficiency drive.
WEG
www.weg.net
Instrumentation Monthly October 2022
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