Houghton carries out on-site motor testing at LNG terminal04 August 2021

National Grid operates a Liquid Natural Gas (LNG) terminal at the Isle of Grain in Kent, the largest LNG facility in Europe with a throughput capability of 15 million tonnes per annum.

A series of 6.6kV blower motors operate on the site. Given the critical nature of the operations at the site it is essential to minimise unplanned downtime for all assets and carry out planned maintenance in periods when demand is lower.

Houghton International was contracted by National Grid to carry out regular testing on a number of motors at the LNG Grain facility as part of a condition monitoring regime to assess the quality of the HV insulation and the dielectric properties of the motor windings.

During periodic site visits, engineers from Houghton International carried out tests on the high-voltage motors to monitor and log the condition of the electrical insulation of each asset. By carrying out the testing periodically, the engineers can use the data as a trending measure to identify motors showing high levels of partial discharge or other signs of insulation material deterioration or aging.

The test regime consists of Partial Discharge (PD) testing and a range of high voltage Baker tests, including:

  • Low resistance and impedance
  • Insulation resistance (IR)
  • Polarisation index (PI)
  • HiPot test
  • Surge interturn test

Collectively these tests can identify a range of insulation and winding issues, both turn-to-turn and phase-to-phase, providing a thorough assessment of the motor’s condition.

Reports are provided that give a summary of test results and a clear pass-or-fail indicator for each test. Further analysis of each motor highlights recommendations for ongoing monitoring, or, where results show signs of insulation aging or deterioration, recommendations for overhaul.

When a scheduled overhaul is required, this is carried out in Houghton International’s 120,000 sq ft facility. This could range from minor maintenance to a full rewind, all of which can be carried out in-house.

Rewinds are carried out using Houghton International’s HiFLEX coils, which are manufactured in-house for complete control over quality and lead time, better windability, more protection from moisture and contaminants, and reduced partial discharge.

Ashley Smith, National Grid LNG terminal electrical engineer, said: “Without Houghton International we would not have identified the deteriorating condition of a number of critical motors that could have failed in service, with implications leading to potentially large commercial costs for the terminal.”

Operations Engineer

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Houghton International Electrical Services Ltd

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