NEN EN ISO 4126-5 : 2013 AMD 1 2016

Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and units
5 Design
   5.1 General
   5.2 End connections
   5.3 Minimum requirements for springs
   5.4 Materials
   5.5 Requirements and procedures
6 Production testing
   6.1 Purpose
   6.2 General
   6.3 Hydrostatic testing
   6.4 Pneumatic testing
   6.5 Adjustment of cold differential test pressure
   6.6 Seat leakage test
   6.7 Pressure seals
7 Type testing
   7.1 General
   7.2 Tests to determine operating characteristics
   7.3 Tests to determine flow characteristics
   7.4 Records and test results
   7.5 Determination of the coefficient of discharge
   7.6 Certification of coefficient of discharge
   7.7 Certification of CSPRS
8 Determination of CSPRS performance
   8.1 Determination of coefficient of discharge
   8.2 Critical and subcritical flow
   8.3 Discharge capacity at critical flow
   8.4 Discharge capacity for any gas at subcritical flow
   8.5 Discharge capacity for non-flashing liquid as the
        test medium in the turbulent zone where the Reynolds
        number R[e] is equal to or greater than 80000
9 Sizing of main valves
   9.1 General
   9.2 Valves for gas or vapour relief
   9.3 Calculation of capacity
10 Marking and sealing
   10.1 Marking on the shell of the main valve
   10.2 Marking on an identification plate
   10.3 Sealing of a CSPRS
Annex A (informative) Examples of sizing calculations for
        various fluids
      A.1 Capacity calculations for gaseous media at critical
          flow (see 9.3.3.1)
      A.2 Capacity calculations for gaseous media at
          subcritical flow (see 9.3.3.2)
      A.3 Capacity calculations for liquids (see 9.3.4)
Annex ZA (informative) Relationship between this European
         Standard and the Essential Requirements of
         EU Directive 97/23/EC (PED)

Defines the requirements for controlled safety pressure relief systems (CSPRS) irrespective of the fluid for which they are designed.