Repair of hydropower station turbine casings to a tight deadline

Repairing the turbine casing

Background

As part of a contract with First Hydro, Kvaerner Boving undertook an on-site Engineering Critical Assessment of the spiral casing of turbines at Ffestiniog Power Station. Defects were found in 2 units, which required repair within the maintenance outage period.

Objective

Kvaerner Boving were required to project manage the removal of the defects and the completion of the repairs within 10 days

Approach

TWI were contracted by Kvaerner Boving to provide assistance and technical support in undertaking the following:

to review all existing materials data and non-destructive examination results
to develop defect removal and welding repair procedures
to test and approve the procedures
to identify and commission suitable welding contractor
to project manage and supervise the on-site repair activities

Benefit

Repair completed in 8 days allowing First Hydro to return the 2 units, each capable of generating 90 MW of electricity, to full and unrestricted operation within the outage period

Conclusion

Use of personnel with broad welding engineering and industrial experience enabled the repairs to be completed within the outage period, with decisions being taken on-site in real time.