Failure Analysis of High-Pressure Cooling System in Boiler Water Circulating Pump at PLTU Paiton Unit 9

Abstract

The Boiler Water Circulating Pump (BWCP) at PLTU Paiton Unit 9 plays a critical role in forced circulation within the boiler system, ensuring the return flow of boiler water from the steam drum to the lower header. This study investigates the failure of the high-pressure cooling system in BWCP, focusing on a specific case where a rupture occurred in the cooling pipeline. Material inspections, trending analysis, and ultrasonic thickness testing were employed to identify failure mechanisms. The findings reveal that a substandard pipe joint—connecting a 5 mm pipe to a 3 mm pipe—caused localized stress and rupturing due to restricted thermal expansion. The resulting breach allowed high-temperature (357°C), high-pressure (180 bar) boiler water to enter the motor, damaging the winding insulation and rendering the motor inoperable. This failure highlights the importance of adhering to proper material thickness standards and performing routine inspections to prevent catastrophic pump breakdowns in high-pressure systems.