0.625%Di
The standard for the concavity of the head in ASME standards is that the concavity shall not exceed 0.625% Di. Specifically, the gap between the cross-sectional shapes of the head must be strictly controlled, with an outward protrusion not exceeding 1.25% Di and an inward concavity not exceeding 0.625% Di, to ensure that the geometric shape of the head meets the design requirements.
In addition, the ASME standard also specifies other inspection standards during the head manufacturing process, including shape and size inspection, non-destructive testing, and surface quality inspection. Shape and dimension inspection includes requirements for cross-sectional shape gaps, straight edges, inclination and wrinkles, roundness tolerances, and other aspects. Non destructive testing ensures the internal quality of the head through methods such as X-ray inspection and ultrasonic testing. Surface quality inspection focuses on surface defects, weld quality, and material surface treatment.
The strict implementation of these standards is an important measure to ensure that the quality of the head meets safety requirements and to ensure the safe operation of the equipment.