BS 6759-3:1984

Foreword
Committees responsible
Specification
Section one. General
1. Scope
2. Definitions
Section two. Material requirements and limitations
3. Pressure containing components
4. Spring materials
5. Other internal parts
Section three. Design and construction
6. General
7. Springs
Section four. Production testing and inspection
8. General
9. Safety
10. Pressure tests
11. Repairs
12. Test certificate
Section five. Marking and preparation for despatch
13. Body marking
14. Identification plate
15. Preparation for despatch
Section six. Performance testing
16. Type testing of safety valves for operating and
     flow characteristics using steam, air, water or
     other gases or liquids of known characteristics
17. Type tests to determine operating characteristics
18. Type tests to determine flow characteristics
19. Determination of coefficient of discharge and
     certified discharge capacity
20. Equivalent capacity
Appendices
A. Guidance on safety valve types and features
B. Relationship between pressure terms used to
     describe safety valve characteristics and the
     requirements of the system to be protected
C. Flow areas
D. Guidance on safety valve installation
E. Provision of information
F. Preferred connection sizes
G. Derivation of compressibility factor Z
H. Determination of average values of M, gamma, Tc
     and pc for gas mixtures
Tables
1. Materials for pressure containing components
2. Spring materials
3. Stress correction factor for curvature (K)
4. Load/length tolerances
5. Spring rate tolerances
6. Inside diameter tolerances
7. Free length tolerances
8. Minimum duration of pressure test
9. Seat leakage rates
10. Values of C relative to values of k
11. Capacity correction factors for back pressure (kb)
12. Flow areas
13. Valve data for conventional, balanced bellows and
     balanced piston valves
14. Maximum pressure ratings for different temperature
     ranges
15. Properties of gases
Figures
1. Safety valve layout and components
2. Illustration of an end coil
3. Spring plate
4. End-squareness
5. End-parallelism
6. Typical test rig for determination of valve
     leakage rates
7. Compressible factor Z as a function of reduced
     pressure pr and reduced temperature Tr
8. Capacity correction factor for viscosity (f mu)
9. Typical pressure term relationships
10. Illustration of area definitions

Requirements for the design, selection and flow certification of safety valves for use with process fluids.