Guidelines for Periodic Inspection of Saturated Steam Spherical Pressure Vessels

These Guidelines apply to periodic inspections of spherical pressure vessels using saturated steam as the medium for heat storage, energy storage, or thermal storage. Inspection bodies shall review design, manufacturing, modification and major repair, operation management, and previous inspection records; develop vessel-specific inspection plans based on risks such as alkaline corrosion, alkaline stress corrosion cracking, and corrosion fatigue; and conduct internal inspections after opening the vessel. The first inspection shall apply recordable ultrasonic testing to 100% of butt joints, while subsequent inspections shall cover no less than 20%. The inspection interval shall be shortened where records are incomplete, post-weld heat treatment is non-compliant, operating parameters exceed limits, or significant corrosion or cracks are found. Vessels without required water-quality testing or with non-compliant results accounting for 10% or more shall be rated Grade 4 and subject to monitored operation for no more than one year.