AS 2809.3:2021 Road tank vehicles for dangerous goods Part 3: Road tank vehicles for compressed liquefied gases.
2.2.3 Outlet protection
Each connection shall be provided with a protective closure secured by a chain. A bleed system shall be
provided between the valve and the closure, see also Clause 2.7.5.
2.2.4 Control of tank quick-closing valves
The control mechanism for quick-closing valves shall incorporate at least two remote means of closing. Such remote means of closing shall be either:
(a) provided with a heat sensitive device which will operate to close the valve at a temperature not exceeding 120 °C; or
(b) actuated pneumatically In accordance with Clause 22.214.171.124.
The remote means of closing should be installed at each end of the tank and diagonally opposite each other.
2.2.5 Excess-flow valves
Excess-flow valves shall close automatically at a rate of flow of vapour or liquid not exceeding 150 % of the design flow rate of the system and —
(a) incorporate a bypass having an opening not greater than 1.0 mm diameter to allow equalization of pressure; or
(b) have manual means of equalization of pressure.
NOTE It is recognized that certain types of cargo may cause malfunction of excess-flow valves and non- return valves. Any proposal to omit such valves for this reason should be referred to the relevant authority for specific approval.
2.2.6 Installation of excess-flow valves
Excess flow valves shall be installed in piping in the following locations:
(a) In the piping on the tanker side of the isolation valve at bulk transfer and vapour return connections outboard of any interconnecting pipework or component such as a pump or a meter.
(b) Adjacent to isolation valves in piping supplying hoses (preferably downstream of the isolation valve).
Any excess flow valve shall be installed so that any liquid or vapour line downstream from it has a flow capacity greater than the rated closing flow of the valve.
NOTE To achieve this flow capacity, the line should normally be not less in diameter than the nominal diameter of the excess-flow valve connection.
2.3 Safety valves
2.3.1 Provision of safety valves
Safety valves shall he provided as required in AS 1210 with the following qualifications:
(a) A safety valve shall communicate with the vapour space of the tank when the tank is at rest in its normal operating position.
(b) The aggregate discharge capacity of safety valves shall be not less than that determined in accordance with Appendix A.AS 2809.3 pdf download.