Component:

• Vertical reheat steam mixer at a Finnish power station

Objective:

• Proving of optical fibre distributed-temperature monitor by field trial
• To determine the global temperature distribution around the drain of the mixer, where previous failures have occurred

Issues:

• Extremely small window of opportunity to install equipment
• Large mixer mass requires several days to cool to allow access

Approach:

• Optical fibre system and replacement insulation system produced in advance of plant shutdown
• Armoured fibre spot-welded using techniques developed beforehand

Results:

• Installation completed and tested within shutdown timescales
• Successful monitoring of start-up and automatic drain operation achieved
• Demonstrated that automatic drain operation leads to large temperature variations between top and bottom of the drain
• Change in drain procedure shown largely to eliminate this thermal gradient

Benefits:

• Global temperature distribution provided information as to the root cause of the problem
• Minor changes to drain procedure eliminated thermal stress and hence fatigue damage
• Extremely low cost of residuals left on plant