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The welding joint coefficient φ for pressure vessels should be determined based on the weld pattern of the butt joint and the length proportion of non-destructive testing. According to GB/T 150-2011 “Pressure Vessels”: For welded joints of steel pressure vessels: 1. For double-sided butt joints and fully penetrated butt joints equivalent to double-sided welding: 1) When all non-destructive testing is conducted, φ = 1.0 ； 2) Local non-destructive testing, take φ=0.85. 2. Single-sided welded butt joint (with gussets in close contact with the base metal along the entire length of the weld root) 1) Full non-destructive testing, take φ=0.9 ； 2) Local non-destructive testing, take φ=0.8. Requirements for non-destructive testing: 1. Technical requirements for radiographic testing – Welded joints shall be subjected to radiographic testing in accordance with JB/T 4730; the acceptable criteria are shown in the table above. 2. Technical requirements for ultrasonic testing: Ultrasonic testing of welded joints shall be carried out in accordance with JB/T 4730; the qualified criteria are shown in the table above. 3. Technical requirements for surface inspection: Magnetic particle and penetrant testing shall be carried out on the welded joints in accordance with JB/T4730, with the acceptance level being no lower than Grade I. 4. Requirements for combined inspection techniques: When radiation and ultrasonic inspection are used in combination, the quality requirements and acceptance levels are determined in accordance with the respective applicable standards, and both must meet those standards.