Steam Blowdown Pressure Vessel.

Steam blowdown vessels in coal-fired power stations receive high-temperature, pressurised water discharged from boiler systems during continuous or intermittent blowdown. Within the vessel, the pressure is reduced so part of the water flashes into steam, allowing the steam and remaining hot water to be safely separated, vented, recovered or directed to the plant drainage system.

The vessel must withstand rapid pressure and temperature changes, thermal cycling, internal erosion and corrosion while safely containing and controlling each blowdown discharge.

MEA was engaged by CS Energy to manufacture and test a new boiler steam blowdown pressure vessel for Callide Power Station Unit B. Due to the vessel's operating pressure, temperature and critical service conditions, all fabrication was completed under controlled pressure-vessel manufacturing procedures using qualified pressure welders, approved welding procedures and fully traceable materials.

The vessel incorporated forged and finish-machined nozzle necks and pipe connections, manufactured to achieve the required flange interfaces, weld preparations, bore dimensions and pressure-boundary integrity. Torispherical dished ends were manufactured to suit the vessel shell, with all pressure-retaining components dimensionally inspected before assembly. Material certificates, weld consumables and component identification were controlled throughout fabrication to maintain complete traceability.

Pressure-retaining welds were completed in accordance with approved welding procedure specifications, including controlled preheating, interpass-temperature monitoring and controlled cooling to minimise residual stress, cracking and distortion. Weld preparation, fit-up, root penetration and final weld profiles were inspected throughout manufacture, with critical weld areas subjected to 100 percent independent magnetic particle inspection.

Following completion, the vessel underwent a CS Energy witnessed hydrostatic pressure test at 1,050 kPa to verify the integrity of the pressure boundary, welded joints, nozzles and associated connections, before being abrasive grit blasted, protective coated and prepared for transport and installation at Callide Power Station.