scope:

FOREWORD

This addendum provides capacity factors for overpressure protection of pressure vessels and pressure equipment for a number of new refrigerants and expands the coverage of capacity factors for existing refrigerants based on the design pressure for the portion of the system being pressure protected. Because the capacity factors are now dependent on the equipment's design pressure, there will be cases where the revised capacity factors are larger than individual values for grouped refrigerants provided in previous editions to this standard. Such cases will not necessarily dictate a larger relief valve for a given piece of equipment, because many pressure vessels will have a relief device that has a modestly larger capacity compared to the calculated minimum required relief capacity for the pressure vessel. In addition, this addendum introduces a method for calculating pressure relief capacity factors for refrigerants not included in the standard or for design pressures for current refrigerants that are outside of the ranges of pressures listed in the pressure relief capacity factor tables.

Note: In this addendum, changes to the current standard are indicated in the text by underlining (for additions) and (for deletions) unless the instructions specifically mention some other means of indicating the changes.