DIN EN 13648-3:2003-01

Foreword
1 Scope
2 Normative references
3 Calculation of the total quantity of heat transferred
  per unit time from the hot wall (outer jacket) to the
  cold wall (inner vessel)
  3.1 General
  3.2 For conditions other than fire
  3.3 Under fire conditions
4 Calculation of the mass flow Q[m] (kg h[-1]) to be
  relieved by the safety devices
5 Rule for the safety devices
6 Sizing of safety devices
  6.1 Safety valves
  6.2 Bursting disc
  6.3 Sizing of safety valves and bursting discs
Annex ZA (informative) - Clauses of this European Standard
                         addressing essential requirements or other
                         provisions of EU Directives
Bibliography

Gives a separate calculation method for determining the contributing mass flow to be relieved.