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Repair of 51-tonne compressor motors wins AEMT award

01 December, 2022

A project that helped to safeguard the UK’s energy supplies by repairing two critical Ex-rated 16MW motors, each weighing 51 tonnes, has been chosen as project of the year in the annual AEMT awards, which were presented recently at a ceremony in Coventry.

The six-phase synchronous motors drive vital compressors at National Grid gas booster stations in Gloucestershire and near Rugby. The VSD-controlled motors help to meet increases in demand by speeding up the compressors to push more gas through the network. The motors have 6.5m-long rotors and operate at a nominal speed of 5,400 rpm and an overspeed of 6,435 rpm.

A problem arose when resistance temperature detectors (RTDs) embedded in the motor windings began to fail, making it difficult to obtain accurate temperature readings and condition monitoring data. National Grid called in Sulzer which decided that a retrofit wasn’t possible because the RTDs were embedded in old windings. It suggested that a turnkey redesign and rewind would be necessary.

Because the six-phase motors have two three-phase windings working side-by-side, the rewind presented multiple challenges.

Each motor had to be removed and transported to Sulzer’s Birmingham service centre. Replacing the RTDs necessitated a complete rewind and reinstallation of the motors, whose stator windings also had to be redesigned to change the position of the RTDs. Additional RTDs were installed in the stators to protect the motors in future. This had to be completed to a tight timescale to minimise disruption to the National Grid infrastructure.

The first motor was reinstalled earlier this year, and since then has provided consistent temperature data to support condition monitoring – thus preserving its Ex compliance. It has helped to ensure reliable gas supplies during a challenging period for the energy sector.

Other winners of 2022 AEMT Awards included:

Product of the year: Preformed Windings for its QualCoil H high-voltage coils, said to be the world’s first Class H resin-rich coil, which took two years and 15,000 hours of R&D to develop.

Service centre of the year: Hayley 247 Engineering Services, which reconditions and repairs industrial gearboxes and pumps with lifting capacities up to 50 tonnes.

The 2022 AEMT awards were presented at a ceremony in Coventry

Supplier of the year: WES – founded in 1990 as Wire Electric Supplies – which provides coil-winding products.

Contribution to skills and training: ADC Electrical, which has collaborated with Primary Engineer to increase awareness of engineering in schools in the Northeast of England.

Rising star: Greig Johnston, who began an apprenticeship with Sulzer in 2018, and has since gained his Level 4 Apprenticeship, a Higher National Certificate and a Higher National Diploma and now wants to start an engineering degree.

Diversity in engineering: Houghton International, which through its policies and employee support initiatives, provides equal opportunities for employment and progression for its staff.

Lifetime contribution: Gary Downes of EMiR Software, who joined the AEMT in 2003 as an associate member. In 2011, he joined the Association’s council and was its first associate member to become honorary president in 2017.

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