1. Intended for hydraulic pressures equal to 8.4 N/mm2 and pipe bore as of 50 mm to 175 mm, flanges and pipes are cast integrally as of re melted cast iron. Flanges are prepared oval and protected with two bolts. Proportions of these pipe joints have been standardised as of 50 mm to 175 mm, bore rising with 25 mm. This kind is added split up into two classes:
(i) Class A: For fluid pressure from 5 to 6.3 N/mm2
(ii) Class B: For fluid pressure from 6.3 to 8.4 N/mm2.
Flanges in every of above classes can be of two types. Type 1 is proper for pipes of 50 to 100 mm bore in class A, and for 50 to 175 mm bore in class B. Flanges of type 2 are stronger than those of Type I and are generally set well back on pipe.
2. For pressures over 8.4 N/mm2 with bores of 50 mm or below, pipe is of formed steel, solid drawn, seamless or rolled. Flanges can be of cast iron, steel combination or forged steel. These are screw or weld on to pipe and are square in increase secured through four bolts. These joints are prepared for pipe bores 12.5 mm to 50 mm increasing in addition of 3 mm as of 12.5 to 17.5 mm and by 6 mm from 17.5 to 50 mm. Flanges and pipes in this group are strong enough for service in pressures range able to 47.5 N/mm2. In every above classes, joint is of the spigot and socket type prepared by a jointing ring of gutta-percha. Notes 1. In case of elliptical and rectangle flanged pipe joints, condition of bending is extremely evidently definite due to flanges being set back on pipe and thickness of flange can be precisely determined to endure bending action due to contraction of bolts.
2. Surfaces forming joint make contact just through a gutta-percha ring on small area give by spigot and recess. Tightening up of bolts squeezes ring into a triangular form and makes a entirely tight joint able of withstand pressure equal to 47.5 N/mm2.
3. Flanges use for high pressure hydraulic pipe joints are intense oval or square in shape, They use two or four bolts which is a huge advantage as assembling and disassembling joint particularly in thin space.
4. Bolt holes are prepared square by enough clearance to contain square bolt heads and to allow for small actions due to setting of joint.