2018 21 Paper: Manapouri cooling water failure

A unitised cooling water system pumps cooling water from the draft tube at a pressure of 450 kPa to the cooling water system on each generating unit at Manapouri Power Station.
Emergency cooling water backup is provided directly from the penstock, with the penstock pressure being reduced via an orifice plate to 450 kPa. In August 2016, during a standard
unit return to service procedure on Unit 1, the cooling water system was over pressurised to full penstock pressure (up to 1700 kPa in places) resulting in burst gaskets, severely damaged pipework, cooler damage, and puddles of water throughout the unit. The failure immediately forced the unit out of service until the cooling water system could be repaired.
The following paper discuses:
• The circumstances leading up to the cooling water failure.
• The Root Cause Analysis of the incident.
• The system design flaws that made this failure possible.
• The challenges and innovative design solutions required to safely return the unit to service as soon as possible.
• The recommendations implemented to ensure a similar failure cannot happen again.

• Author: Mitchell Beggs, Steve Taylor
• Exchange: 2018 - Albury AGL
• Company: Meridian Energy
• Topic: Asset Condition, Asset Replacement, Cooling, Transformer
• Key Words: Control Philosophy, Cooling, Fault, Transformer, Upgrade/Uprate