ISO-13631 and API-618 define the Rated Discharge Pressure as the "highest pressure required to meet the conditions specified by the purchaser for the intended service".

Rated Discharge Pressure is conditional upon the Maximum Allowable Working Pressure based on the guidelines in ISO-13631 and API-618.  The maximum allowable working pressure shall exceed the RDP by at least 10% or 25 psi (1.7 bar), whichever is greater. 

Ariel does allow for operation above the cylinder RDP provided there is ample room for the pressure relief valve range and for a high pressure shutdown device.  Typically, when the operating pressure is above the RDP, a pilot operated relief valve must be used (rather than a spring operated relief valve).  The relief valve must be set no higher than the cylinder MAWP.