13 Jun AUSTRALASIAN HRSG USERS GROUP (AHUG) 2014

STRESS CORROSION CRACKING FINDINGS

Presentation by Anita Zunker, PEI

Due to steam demand at the time that a tube leak was identified, the decision was made to continue to operate the boiler. When opening up the boiler to repair the leaking tube, stress corrosion cracking was identified in a number of areas. Evidence of caustic deposition throughout the furnace was also found.

The same tube leak occurred on the “sister” boiler. It was also knowingly operated with a tube leak due to steam demand. No stress corrosion cracking was found.

The short presentation will overview the timeline of events, the findings, the repair works, and the follow up inspection to ensure that there was no further damage yet to be identified.

SHUTDOWN, LAYUP AND PRESERVATION OF HRSGS

Presentation by Anita Zunker, PEI, with Contact Energy

Contact Energy’s Stratford Power Station GT26 CCGT, also known as  Taranaki Combined Cycle (TCC), operational strategy has changed so that it has periods of short to medium term preservation. A preservation project was kicked off in 2012 in recognition of this change.

In 2014, the GT and HRSG exhaust gas side preservation was an area of focus. Following a review of options, an appropriate exhaust gas side preservation strategy was identified considering issues such as weather (often wet and windy) and the return to service timeframes that the unit required to retain operational flexibility. A GT inlet duct balloon was selected for quick and easy deployment in the GT inlet duct. A stack cage / cap with a custom made cover was installed on the top of the HRSG exhaust stack. Dehumidification was then applied to manage the relative humidity within the spaces after the isolations were put into place.

The presentation demonstrates how the TCC exhaust gas side preservation was implemented.