What are the types of surveys as class and flag state for machinery?

flowchart LR
    A[Class Surveys] --> A1[Special Surveys]
    A --> A2[Annual Survey]
    A --> A3[Survey of Machinery]
    A --> A4[Propeller Shaft]
    A --> A5[Shaft Extension]
    B[Flag State Surveys] --> B1[Initial]
    B --> B2[Intermediate]
    B --> B3[Renewal]
    B --> B4[Partial]
    C[Class acts for Flag] --> A
    C --> B

• Class machinery surveys: Special Surveys, Annual Survey, Survey of Machinery, Propeller Shaft surveys, Shaft extension surveys
• Flag state survey types: Initial, Intermediate, Renewal, Partial
• Class acting for flag: On classed ships, class societies conduct hull and machinery surveys on behalf of flag state
• Confirmatory approach: Surveys rely on maintenance and condition monitoring records rather than strip-down
• Indian flag: Merchant Shipping Act 2025, DGMA authorizes class societies for machinery surveys
• Governing instruments: IACS UR Z15, Z18, Z21; IMO Resolutions A.1053(27), A.997(25), A.491(XII); MSIS23; MS Act 2025