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TEST & MAINTENANCE HOW TO PLAN FOR THE UNPLANNED
The test regime consisted of PD testing and a range of high voltage Baker tests, such as the low resistance and impedance testing, Insulation Resistance (IR), HiPot test and the 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 conducted by Houghton International gave National Grid a clear pass or fail indicator for each test. Further analysis of each motor highlighted recommendations for ongoing monitoring and suggestions for when the motor should be tested again, allowing LNG to establish a clear testing and maintenance schedule. Where results showed signs of insulation aging or deterioration, the reports included recommendations for overhaul.
Houghton explains the importance of a planned preventative maintenance strategy using an example at National Grid’s LNG terminal in Kent
ational Grid operates a Liquid Natural Gas (LNG) terminal at the Isle of Grain in Kent, the largest LNG facility in Europe with a throughput capacity of 15 million tonnes per year. Given the critical nature of operations at the facility, stringent safety controls must be followed and a planned preventative maintenance strategy is crucial to the functioning of the terminal. To ensure the strategy was implemented in an effective way, electro mechanical specialist Houghton International was called to assist.
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The LNG facility operates a series of 6.6kV blower motors. Since the plant provides essential services, it is crucial to minimise unplanned downtime for all assets and carry out maintenance during planned intervals. Houghton International was contracted by National Grid to carry out periodic testing on a number of motors at the facility. The
condition monitoring regime assessed the quality of the HV insulation and the dielectric properties of the motor windings.
The importance of testing Houghton International’s site services team managed the whole process of testing, decommissioning, removal, transportation, overhaul or rewind, reinstallation and recommissioning at Grain LNG, making operations simpler and smoother for National Grid.
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. The engineers used the data as a trending measure to identify motors showing high levels of Partial Discharge (PD) or other signs of insulation material deterioration or aging.
These overhauls, which ranged from minor maintenance to full rewinds, were carried out in Houghton International’s 120,000 square foot facility in Newcastle-upon-Tyne. Rewinds were completed using Houghton International’s HiFLEX coils, which are manufactured in-house by Houghton International. This gives the company full confidence that it can deliver a quality product within the lead time specified. Houghton’s coils also offer better windability, more protection from moisture and contaminants, and reduced Partial Discharge. In one recent rewind, the motor’s Partial Discharge reading was independently verified, demonstrating a reduction in PD from 5041pC to 220pC (Pico Coulombs).
Avoiding motor failure
By carrying out regular testing, Houghton International could identify which motors were deteriorating, allowing LNG to carry out any necessary repairs before this led to an unanticipated failure.
“At Houghton International we believe a periodic testing regime is important for all industries but especially those that perform critical operations,” commented Chris Measor, Winding Assistant Manager of Houghton International. “A well-planned preventative maintenance strategy is key to the dependable, long-life operation of electric motors. This is why we continuously invest in the latest equipment to provide a comprehensive range of testing, repair and maintenance services for our customers.” “Without the testing regime implemented by Houghton International, several of our critical motors could have failed in service, leading to large commercial costs for the terminal,” explained Ashley Smith, LNG Terminal electrical engineer.
Storage tanks for LNG on the Isle of Grain Source: Shutterstock
Houghton International
www.houghton-international.com
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