Metalock Blog – News onsite engineering services and all things metalock

PRESS RELEASE

---

June 28th, 2010

ESB Turbine – casing rebore for reblading By replacing internal corroded areas of a Parsons steam turbine with improved materials the unit has beengiven a new lease of life at modest cost compared with the possible alternatives for the ESB, the leadingelectricity company in the Republic of Ireland. The Coventry firm Metalock Engineering UK was appointed byTurbine Blading, who had the main contract for design and project management, to carry out the in-situ machiningwork on the turbine.

During a scheduled overhaul that involved opening up the main load turbine at Shannonbridge, Co Offaly, anunacceptable degree of pitting and erosion was evident on the casing and cover between blade rows 32 to 35,the condensation area of the unit. In addition, 4 rows of fixed blading were also affected. ESB managementdecided to repair the lower casing and cover by reblading the affected area, but at the same time upgrade thecasing surfaces to better resist corrosion and to maintain original blade radial clearances.

Metalock and Turbine Blading Ltd evaluated the possibilities of repair and Metalock was subsequently appointedto do the work. This involved removing the affected fixed blades, machining the areas between them to acceptsemi-circular inserts, and recutting one side of the serrations in line to accept new caulking pieces.

Work to the lower half casing was carried out in-situ in its operating position whilst that on the cover wasperformed in an adjacent loading bay. To remove the four rows of blades, Metalock engineers devised atooling system to cut away the centre of the existing caulking pieces without cutting into the serrations of eitherthe blading or the casing. Once a row was completed, the blades in packets of six, were easily removed.

Machining between the blade rows to remove corrosion and prepare for inserts meant that one side of thecaulking piece casing serrations would be cut away. Once each semi-circular stainless steel insert was put inplace in its machined groove and secured with two rows of M6 stainless steel cap head screws, the serrationswere recut one side in line with those facing to a tolerance of ±0.025mm.

Following installation of replacement blades, the turbine was reassembled and put on test which it passedwithout problem.

Machining to remove the four rows of bladeson the turbine casing cover was done in anadjacent bay by using a cooling system to cutaway the centre of the existing caulking pieceswithout cutting into the serrations.

---

Contact:
Metalock Engineering UK Ltd.
Unit H5 Pilgrims Walk, Prologis Park, Coventry CV6 4QG ENGLAND
Tel: +44 (0) 2476 338205
Fax: +44 (0) 2476 360190