Frequency of meter proving will generally be set by the Regulating Authority concerned if a Fiscal type system. Otherwise the frequency will depend upon the actual process conditions,fluid quality (clean/ dirty etc.) & obviously the level of uncertainty you need to obtain.
As a general point, master meters are typically used in the Petrochemical Industry in conjunction with a reliable secondary standard, Vol tank or displacement prover. This allows them to be checked on the actual fluid before comparison with the service meter. Where only a master meter is used, this is really only a "check" not a proving. You should bear in mind that all meters deviate for various reasons, wear, damage, viscosty effects etc.So actual cal in situ on the process fluid at operating conditions, provides a much more complete picture than a "check" meter.Don't assume master meter installations or services are necessarily "cheap", they can be very disruptive to normal operations & "good" rigs are fairly expensive to hire.
