Create a new specification same form and fit as AS4751. This specification will include /1 coupling, /2 sheet metal flange and /3 solid flange. Define new operating, proof and burst pressures. This will have QPL requirement.
Currently the AS4751/1 coupling is not able to pass proof tests. Table 2 pressures need to be adjusted to an achievable level. Currently this is not on a QPL and there is no way to know who is so a new specification is required.