The proportion of the weld shall be as indicated in the Fig. Nos. 28, 29, 30, 30A, 31, 32, 32A, 33, 34, and  34A of the following types:-

Type
1. Welding Neck flange. Figure 28
2. ‘Face and Back’ welded- on flange for metal arc welding Figure 29.
3. ‘Bore and Back’ welded – on flange for metal arc welding. Figure 30 and 30A.
4. ‘Face and Fillet’ welded – on flange for metal arc welding. Figure 31.
5. ‘Bore and Fillet’ welded – on flange for metal arc welding. Figures 32 and 32-A.
6. ‘Slip on’ welded – on flange for metal arc welding. Figure 33
7. ‘Slip on’ welded – on bossed flange for oxy-acetylene welding. Figure 34.
8. 'Socket welded flange Figure 34A.

The flange shall not be a tight fit on the pipe.

The maximum clearance between the bore of the flange and the outside diameter of the pipe shall be 3 mm. (1/8”) at any point, and the sum of clearances diametrically opposite shall not exceed 5 mm (3/16 in).

NOTE:- All dimensions shown in the figures of types 1 to 7 relate to finished sizes.

The design conditions for each type are as follows:-

Type 1,2 and 3 flanges for all design pressure and temperature conditions.

Types 4 and 5 flanges for all pressure conditions up to and including 42 kg/cm² (600 lbs./sq. in.) and design temperature not exceeding 399 °C.(750 °F).

Types 6 and 7 flanges for all pressure conditions up to and including 17.6 kg/cm² (250 lbs. sq. in) and temperature not exceeding 399°C. (750 °F) except that Bossed flanges of type 6 shall not be used on pipes over 304 mm (12”) in nominal bore, nor Bossed flanges of type 7 on pipes over 152 mm. (6”) in nominal bore.

Type 8 flanges for all design pressure and temperature conditions. This type shall be used only for pipes upto and including 51 mm (2 inches) nominal bore. These flanges shall not be used where severe erosion or corrosion is expected to occur.