BS 137-2:1973

Co-operating organizations
Foreword
Specification
1 Scope
2 Definitions
3 Materials, workmanship and finish
4 Design and construction
5 Mechanical loads
6 Ball and socket couplings for string insulator units
7 Screw threads of pin insulators
Appendices
A Selection and application of the line insulators
B Dimensions of pin and line post insulator heads
   reflecting current British practice
C Dimensional and mechanical characteristics of string
   insulator units of the cap and pin type either with
   ball and socket couplings or with clevis and tongue
   couplings
Tables
1 Minimum failing loads
2 Power-frequency and impulse withstand voltages
3 Recommended test voltages and radio interference
   noise limits
4 Specified values of mechanical and dimensional
   characteristics for string insulator units with ball
   and socket couplings
5 Specified values of mechanical and dimensional
   characteristics for string insulator units with
   clevis and tongue couplings
Figures
1 Gauge for screw threads of pin insulators for use
   with pins with small steel heads
2 Gauge for screw threads of pin insulators for use
   with pins with large steel heads
3 Head of porcelain insulator normally used on 11 kV
   lines
4 Head of porcelain insulator normally used on 33 kV
   lines

Materials, workmanship, finish, design and construction. Mechanical loads (minimum failing loads), ball and socket couplings for string insulator units, screw threads for pin insulators. Appendices on selection and application and dimensions of pin and line post insulator heads.