A failed furnace transformer at Corus’ integrated iron and steel plant in Scunthorpe may have cost the company lost production - until ABB’s fast-track on-site diagnostic and repair service came to the rescue.
ABB’s on-site transformer diagnostic and repair service, that effectively takes a comprehensive transformer refurbishment facility to the customer’s site, helped Corus in Scunthorpe to return one of its plants to full production less than 10 days after the failure of one of its 132/33 kV furnace transformers at its Basic Oxygen Steelmaking. (BOS) plant in February.
Corus in Scunthorpe is the UK’s largest integrated steel plant, with the capacity to produce 4.5 million tones per annum. The steelworks has three furnace transformers within the BOS plant, but when one of them failed unexpectedly it reduced the plant’s ability to manufacture some of the technically challenging grades of steel. Taking the transformer off-site for a factory repair would have taken a minimum of six weeks, while the current lead-time for a brand new transformer is anything from 18 months to two years. With each week without the transformer affecting Corus’ production, a speedy solution was essential, so ABB’s UK power systems service team was called in to investigate possible alternatives.
Diagnostic tests
The first step for the ABB team was to carry out a battery of tests on the failed transformer using a sophisticated suite of non-invasive diagnostic techniques. These tests established quickly that the fault was in the transformer tap-changer located within the main tank. This is quite a common problem with furnace transformers as they operate under very severe conditions compared to transformers in power network applications, with frequent cyclic loading due to the operation of the high voltage circuit breaker as well as overcurrents and overvoltages generated by short circuits in the furnace.
The good news for Corus was that ABB’s newly developed on-site repair service now made it possible for the transformer’s active parts to be removed from the tank so that access could be gained to the faulty tapchanger. This enabled all the failed components to be replaced on-site, in a fraction of the time required for a factory repair.
On-site repair
Corus asked ABB to start work immediately, and ABB’s on-site repair team, comprising two transformer engineers and a transformer fitter, with the assistance of one of ABB’s furnace transformer experts flown in specially from Sweden, went straight to the site. Their first task was to decommission the transformer. Then a local heavy lifting specialist was called in to help move the transformer to another part of the site, where there would be better access and more space to establish a temporary, fully-equipped, workshop, complete with clean room.
Working round the clock, the ABB team de-tanked the transformer, repaired it, reassembled it and tested it on the spot. A key element in the repair process was ABB’s capability to carry out high voltage tests and to commission the transformer ready to return to service, with all this completed just 14 days after the transformer failure was first reported. The work was carried out to exactly the same high standards that would be expected of a factory repair, with every phase conducted strictly to ISO 9001 and ISO 14001 procedures.
Liam Warren of ABB’s UK power service operation said: “Our on-site diagnostic and repair service has already established a growing reputation in the power transmission and distribution industry, but this is the first time that it has been used by an industrial process customer. Again, it has proved the ideal and most cost-effective route to ensure a fast return to service with minimal disruption. Corus was delighted with our speedy initial response and the time it took to carry out the repairs.”
ABB Background
ABB (www.abb.com) is a leader in power and automation technologies that enable utility and industry customers to improve their performance while lowering environmental impact. The ABB Group of companies operates in around 100 countries and employs about 115,000 people.