ONORM EN ISO 23251 : OCT 2008

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Causes of overpressure
  4.1 General
  4.2 Overpressure protection philosophy
  4.3 Potentials for overpressure
  4.4 Recommended minimum relief system design content
  4.5 List of items required in flare-header calculation
       documentation
  4.6 Guidance on vacuum relief
5 Determination of individual relieving rates
  5.1 Principal sources of overpressure
  5.2 Sources of overpressure
  5.3 Effects of pressure, temperature, and composition
  5.4 Effect of operator response
  5.5 Closed outlets
  5.6 Cooling or reflux failure
  5.7 Absorbent flow failure
  5.8 Accumulation of non-condensables
  5.9 Entrance of volatile material into the system
  5.10 Failure of process stream automatic controls
  5.11 Abnormal process heat input
  5.12 Internal explosion (excluding detonation)
  5.13 Chemical reaction
  5.14 Hydraulic expansion
  5.15 External pool fires
  5.16 Jet fires
  5.17 Opening manual valves
  5.18 Electric power failure
  5.19 Heat-transfer equipment failure
  5.20 Vapour depressuring
  5.21 Special considerations for individual pressure-relief
       devices
  5.22 Dynamic simulation
6 Selection of disposal systems
  6.1 General
  6.2 Fluid properties that influence design
  6.3 Atmospheric discharge
  6.4 Disposal by flaring
  6.5 Disposal to a lower-pressure system
  6.6 Disposal of liquids and condensable vapours
7 Disposal systems
  7.1 Definition of system design load
  7.2 System arrangement
  7.3 Design of disposal system components
  7.4 Flare gas recovery systems
Annex A (informative) Determination of fire relief requirements
Annex B (informative) Special system design considerations
Annex C (informative) Sample calculations for sizing a subsonic
                      flare stack
Annex D (informative) Typical details and sketches
Annex E (informative) High integrity protection systems (HIPS)
Bibliography

Applies to pressure-relieving and vapour-depressuring systems.