NEN EN 331 : 2015

Foreword
1 Scope
2 Normative references
3 Definitions
4 Classification
4.1 Pressure classes
4.2 Temperature classes
5 Construction requirements
5.1 General
5.1.1 Materials
5.1.2 Construction
5.1.3 Connections
5.1.4 Seals
5.2 Operation
5.3 Stops
5.4 High temperature resistance
6 Performance requirements
6.1 General
6.2 Leak-tightness
6.3 Rated flow rate
6.4 Operating torque
6.5 Torque and bending resistance
6.6 Durability
6.6.1 Endurance
6.6.2 Resistance to low temperature
6.7 Stop resistance
7 Test methods
7.1 General
7.1.1 Test conditions
7.1.2 Test sequence
7.2 Leak-tightness
7.2.1 General
7.2.2 Closure parts, external leak-tightness
7.2.3 Internal leak-tightness
7.3 Rated flow rate
7.3.1 Apparatus
7.3.2 Procedure
7.4 Operating torque
7.5 Torque and bending resistance
7.5.1 General
7.5.2 Sequence of torsion and bending moment tests for
       valves
7.5.3 Procedure for valves with flexible connection (see
       Figure 5)
7.6 Durability
7.6.1 Endurance test
7.6.2 Resistance to low temperature
7.6.3 Durability of sealing materials
7.6.4 Protection pf external surfaces
7.6.5 Resistance to humidity
7.7 Angular seal
7.8 Stop resistance
8 Marking, installation and operating instructions
       and packaging
8.1 Marking of the valve
8.2 Installation and servicing operating instructions
8.3 Packaging
Annex A (informative) Leak-tightness test - Volumetric
         method
Annex B (informative) Leak-tightness test - Pressure loss
         method
Annex C (informative) High temperature resistance
Annex D (informative) A-deviations
Annex E (informative) Bibliography

Defines the characteristics for the construction, performance and safety of ball valves and closed bottom taper plug valves. Also details the test methods and marking provisions.