Function of Bolt and Nuts

Function of Bolt and Nuts

Application of Bolts

  • For flanged joints in piping system where one or both flanges are of cast iron, bolts / studs conforming to ASTM A307 Gr. B and nuts conforming to A194 Gr. 2 are usually used. Equivalent IS standards for such fasteners is IS 1367 CI. 6.6 / IS 1367 CI. 6.
  • For carbon steel flanges having ASME 150 rating on non-critical services, bolts / studs conforming to ASTM A307 and nuts conforming to ASTM A194 Gr. 2 or fasteners conforming to IS 1367 CI. 6.6 / IS 1367 CI. 6 are usually used.
  • For carbon steel flanges on process and critical services involving medium and moderately high pressures and temperatures, bolts / studs conforming to ASTM A193 Gr. B7 along with heavy hexagonal head nuts conforming to ASTM A194 Gr. 2H are usually used.
  • For very severe service conditions involving high temperatures upto 1100°F bolts /studs conforming to ASTM A193 Gr. B7 along with nuts conforming to ASTM A194 are usually used.
  • For low temperature carbon steel flanges, studs conforming to ASTM A320 Gr. L7 along with nuts conforming to ASTM A194 Gr. 4 are usually used.
  • For all flange joints in plastic piping, low strength bolts / studs are usually acceptable. Use of washers is recommended for joints in plastic piping.
  • Sometimes in plastic piping, handling corrosive fluids, it is recommended that the fasteners are supplied with cadmium plating or galvanized coating. This is in order to have corrosion resistance against spillages, etc.