What Pipe Flange should I use based on Steam pressure according to Indian Boiler Regulation?

Is there any regulation that standardized the pipe diameter and thickness for the steam pressure? Yes, there is a regulation in India called the Indian Boiler Regulation, in short IBR which is created on 15th September 1950 to regularise the manufacturing of boilers, steam generators, and steam distribution piping systems. For the manufacturers and the consumers of boiler or steam distribution piping systems, It is mandatory to follow this regulation and get approval from the concerning authority. In this article, we will understand the 5 classes of pipe flanges in Indian Boiler Regulation (IBR), based on the steam pressure.

Pipe Flanges According to Indian Boiler Regulation (IBR)

Following are the five classes of Indian Boiler Regulation for the pipe dimensions and flange dimensions based on steam pressure inside the pipe.

Class I: This class of pipe flanges is used for the steam pressures up to 0.35 N/mm2 and the pipes used for water pressures up to 1.4 N/mm2. This is not suitable for feed pipes and shocks.

Class II: This class of pipe flanges is used for the steam pressures over 0.35 N/mm² and the steam pressure below 0.7 N/mm².

Class III: This class of pipe flanges is used for the steam pressures over 0.7 N/mm² and the steam pressure below 1.05 N/mm².

Class IV: This class of pipe flanges is used for the steam pressures over 1.05 N/mm² and the steam pressure below 1.75 N/mm².

Class V: This class of pipe flanges is used for the steam pressures from 1.75 N/mm² to 2.45 N/mm².

Following are the important guidelines that we need to follow from the Indian Boiler Regulation

• According to Indian Boiler Regulation (IBR), it is mandatory for classes II, III, IV and V, the diameter of flanges, the diameter of bolt circles and the number of bolts should be identical and that difference should consist in variations of the thickness of flanges and diameter of bolts only.
• The Indian Boiler Regulation also recommends that all nuts should be chamfered on the side bearing on the flange and that the bearing surfaces of the flanges, heads and nuts should be true. The number of bolts in all cases should be a multiple of four.
• The Indian Boiler Regulation recommends that for 12.5 mm and 15 mm bolts, the bolt holes should be 1.5 mm larger and for higher sizes of bolts, the bolt holes should be 3 mm larger.
• All dimensions for pipe flanges having internal diameters 1.25 mm to 600 mm are standardised for the above mentioned classes (I to V). The flanged tees, bends are also standardised.
• As soon as the size of the pipe is determined according to the steam pressure inside the pipe, the rest of the dimensions for the flanges, bolts, bolt holes, thickness of pipe may be fixed from standard tables.

Very important note to use pipe design calculations accoring to IBR

• In practice, dimensions are not calculated on a rational basis. The standards are evolved on the basis of long practical experience, suitability and interchangeability.
• The calculated dimensions as discussed in the previous article do not agree with these standards.
• It is of reader interest only that you should know how to use fundamental principles in determining various dimensions such as wall thickness of pipe, size and number of bolts, flange thickness.
• The rest of the dimensions may be obtained from standard tables or by empirical relations.