iv) Vent outlet automatic closing devices are to be self-draining.
v) The clear area through a vent outlet closing device in the open position is to be at least equal to the area of the inlet.
vi) An automatic closing device is to:
• Prevent the free entry of water into the tanks,
• Allow the passage of air or liquid to prevent excessive pressure or vacuum developing in the tank.
vii) In the case of vent outlet closing devices of the float type, suitable guides are to be provided to ensure unobstructed operation under all working conditions of heel and trim.
viii) The maximum allowable tolerances for wall thickness of floats should not exceed ±10% of thickness.
ix) The inner and outer chambers of an automatic air pipe head is to be of a minimum thickness of 6 mm (0.24 inch).