AS 2809.2:2020 Road tank vehicles for dangerous goods Part 2: Road tank vehicles for flammable liquids.
2.3.2 Compartment openings
Each compartment shall be accessible through an opening of dimensions in accordance with AS 2865 to allow a person to pass through to carry out inspections or maintenance work. Any such opening shall be fitted with a closure.
Except for bolted flange covers designed and manufactured in accordance with AS 1210, all closures for openings into tank compartments, used for access or for maintenance work, and any equipment, such as pressure and vacuum vents and other fittings, shall be regarded as hatch assemblies, and be subject to a drop test (refer to AS 2809.1 Appendix B).
Hatch coamings shall extend no further than 25 mm into tank vapour space unless fitted with a bleed hole into the vapour space.
2.3.3 Valves
Each liquid discharge opening shall be provided with an internal shut-off valve and an external shut-off valve. At the end of the opening a protective cap linked by a tether shall be fitted. These fittings shall be suitable for service at the piping design pressure. The internal shut-off valve shall conform with the following requirements:
(a) The internal shut-off valve seat shall be located inside the tank or within the tank flange or its companion flange.
NOTE The remainder of the valve may be either inside or outside the tank shell, provided that in the event of accidental damage to any associated external fittings, the internal shut-off valve remains intact to minimize loss of cargo.
(b) An internal shut-off valve which is bottom-operated shall incorporate an automatic heat- actuated closing device which will become effective at a temperature of not more than 120 °C, arranged to respond to a fire near the tank outlets.
(c) A tank designed for bottom loading shall incorporate a downward-direction liquid flow deflector above the internal shut-off valve.
(d) A system for opening and closing the internal valves and vapour vents of each compartment shall be interconnected with the road tank vehicle park brake interlock system (see AS 2809.1), to prevent it from being driven or moved while the internal shut-off valves and vapour vents are open.
(e) An internal shut-off valve which is pneumatically-operated shall incorporate a device to enable manual opening if a pneumatic system is inoperable.
2.3.4 Vents
Each tank compartment shall be provided with normal venting in accordance with Clause 2.3.6 and emergency venting in accordance with Clause 2.3.7. The vents and their installation shall conform with the following requirements:
(a) Each vent shall be marked with the manufacturer’s name, model identification, discharge capacity and related pressure.
(b) The discharge capacity of each model and type of vent shall be determined before use. NOTE AS 1271 and API 2000 provide methods for determining flow rating.
(c) Vents shall be designed and fitted, as far as is practical, in the centre of compartments to minimize the discharge of product through the vent in the event of surge or vehicle roll-over. A vent shall be deemed to conform with this requirement if it does not leak after the application of the tests specified in AS 2809.1 Appendix B.AS 2809.2 pdf download.