5.9.1(a) General. The application and pressure ratings (internal and external pressure or vacuum) of mechanical joints are to be approved by ABS. The approval is to be based upon the testing specified in 4-6-2/5.9.2, as required for the service conditions and intended application. 5.9.1(b) Impact on Pipe Wall Thickness. Where the application of mechanical joints results in reduction in pipe wall thickness due to the use of bite type rings or other structural elements, this is to be taken into account in determining the minimum wall thickness of the pipe to withstand the design pressure. 5.9.1(c) Operational Conditions. Construction of mechanical joints is to prevent the possibility of tightness failure affected by pressure pulsation, piping vibration, temperature variation and other similar adverse effects occurring during operation onboard. 5.9.1(d) Materials. Material of mechanical joints is to be compatible with the piping material and internal and external media. 5.9.1(e) Locations. Mechanical joints, which in the event of damage could cause fire or flooding, are not to be used in piping sections directly connected to the sea openings or tanks containing flammable fluids.