9.3.7(c) Materials
i) Casings of vent outlet closing devices are to be of approved metallic materials adequately protected against corrosion.
ii) For galvanized steel air pipe heads, the zinc coating is to be applied by the hot method and the thickness is to be 70 to 100 micrometers (2.756 to 3.937 mil).
iii) For areas of the head susceptible to erosion (e.g. those parts directly subjected to ballast water impact when the tank is being pressed up, for example the inner chamber area above the air pipe, plus an overlap of 10° or more to either side) an additional harder coating should be applied. This is to be an aluminum bearing epoxy, or other equivalent coating, applied over the zinc.
iv) Closures and seats made of non-metallic materials are to be compatible with the media intended to be carried in the tank and to seawater, and suitable for operating at ambient temperatures between -25°C and 85°C (-13°F and 185°F).
9.3.7(d) Type Testing. Vent outlet automatic closing devices complying with 4-6-4/9.3.7(b) and 4-6-4/9.3.7(c), including metallic floats and nonmetallic floats of different types for marine use, are to be certified by ABS in accordance with 4-6-4/9.3.7(d) of the Steel Vessel Rules.
Vent outlet automatic closing devices may be Type Approved, see 1-1-A3/1 of the ABS Rules for Conditions of Classification (Part 1) for general requirements for Type Approval Certification.