Maximum Allowable Working Pressure of Boiler Shell – Indian Boiler Regulations (IBR) 1950
In boiler engineering, the maximum allowable working pressure (MAWP) is one of the most important safety parameters. It defines the highest pressure at which a boiler shell or component can safely operate under the Indian Boiler Regulations (IBR), 1950.
This blog explains the calculation of MAWP for a carbon steel shell plate used in a wet back shell type boiler. The problem is based on a real examination question (CBB Part 2, 2020) and is solved step‑by‑step using IBR Regulation 574.
Problem Statement
A carbon steel plate is used for the fabrication of the shell of a wet back shell type boiler.
- Shell size: 2170 mm OD × 10 mm thickness
- Minimum specified ultimate tensile strength at room temperature: 49 kg/mm²
- Minimum specified yield strength at design temperature: 26 kg/mm²
- Efficiency factor: E = 1.00
Task: Calculate the maximum allowable working pressure (MAWP) of the shell in kg/cm² as per Indian Boiler Regulations, 1950.
Step‑by‑Step Solution
1. Given Data
- Outside Diameter (OD) = 2170 mm
- Thickness (t) = 10 mm
- Ultimate tensile strength (F) = 49 kg/mm²
- Yield strength (Ft) = 26 kg/mm²
- Efficiency factor (E) = 1.00
- Constant (C) = 27 (as per IBR Regulation 574)
- Internal Diameter (ID) = 2150 mm
2. Formula (IBR Regulation 574)
The formula for calculating MAWP of a shell is:
Final Answer
The maximum allowable working pressure (MAWP) of the carbon steel boiler shell is:
7.47 kg/cm² (as per IBR 1950 Regulation 574).
Conclusion
This calculation highlights how boiler engineers apply IBR 1950 rules to determine safe operating pressures. By considering tensile strength, yield strength, efficiency factors, and shell dimensions, engineers ensure compliance with statutory safety codes.
Such problems are frequently asked in boiler certification exams (CBB Part 2) and are highly relevant for professionals working in power plants, refineries, and industrial boiler systems.
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