Introduction
In 1926, committees were formed to develop piping codes aimed at ensuring the safety of operations. These efforts culminated in codes published between 1942 and 1955. Currently, the following codes are enforced under ASME B 31 piping, previously designated by ANSI:
ASME B 31.1: Power Piping
,ASME B 31.3: Process Piping
ASME B 31.4: Liquid Transportation Systems for Hydrocarbon and LPG
ASME B 31.5: Refrigeration Piping
ASME B 31.8: Gas Transmission and Distribution Piping Systems
ASME B 31.9: Building Service Piping
ASME B 31.11: Slurry Piping
ASME B 31.1: Power Piping
Overview
ASME B 31.1 focuses on power piping, encompassing systems for fuel gas, oil, water, and steam in power plants. It provides guidelines for new piping installations and serves as a reference for repairs and replacements. If the limits of B 31.9 are exceeded, the system falls under B 31.1.
Organization of B 31.1
Boiler External and Non-Boiler External Piping
Boiler External Piping: Part of Section I of the B&PV Code; begins at the first weld, flanged face, or threaded joint outside the boiler and extends to required valves.
Non-Boiler External Piping: Entirely within B 31.1.
Systems Covered Under B 31.1
1. Boiler external piping (steam, feedwater, blowoff, drain)
2. Instrument, control, and sampling piping
3. Spray-type desuperheater piping
4. Piping downstream of pressure-reducing valves
5. Pressure-relief piping
6. Piping for flammable and combustible liquids
7. Piping for flammable gases, toxic gases or liquids, or non-flammable non-toxic gases
8. Piping for corrosive liquids and gases
9. Temporary piping systems
10. Steam trap piping
11. Pump-discharge piping
12. District heating and steam distribution systems
Structure of the Code
The code comprises six chapters and 14 appendices, where appendices with letter designations are mandatory, and those with Roman numerals are non-mandatory. All paragraphs fall within the 100 range, with the 100 series outlining B 31.1's sections on pressure piping.
Design Conditions and Criteria
Design Pressure and Temperature
Design conditions must account for the most severe internal pressure conditions, considering factors such as thermal expansion and surge. For boiler external piping, the design pressure must exceed 25% or 225 psi, whichever is lower.
Pressure Design (Internal and External)
Internal Pressure: Design calculations apply to straight pipe and fittings as per specified tables and paragraphs.
External Pressure: Includes checks for membrane stress and buckling.
Pressure Design for Various Components
Welded Branch Connections: Must adhere to reinforcement principles and specified angle requirements.
Bends and Elbows: Must meet minimum wall thickness requirements.
Flanges and Blanks: Follow specific guidelines outlined in relevant paragraphs.
Materials Requirements
Materials must be listed in:
Appendix A
Approved code cases
Referenced standards in Table 126.1
Fabrication, Assembly & Erection
Chapter V outlines rules for welding, including preheating, heat treatment, and types of welded joints. Key points include:
Preheating temperature minimum of 10°C (specific exceptions apply).
Heat treatment must follow prescribed standards.
Examination and Pressure Testing
Non-Destructive Examination
Visual inspection is mandatory, adhering to specific standards.
Types of Pressure Testing
1. Hydrostatic Testing
2. Pneumatic Testing
3. Mass Spectrometer and Halide Testing
4. Initial Service Testing
Hydrostatic testing requires a pressure of 1.5 times the design pressure. Pneumatic testing may substitute hydrostatic testing under specific conditions.
Conclusion
Understanding these codes is crucial for ensuring safe and efficient piping operations across various applications. Compliance with ASME B 31 codes helps maintain high safety and operational standards in piping design and installation.
“The content of this article is taken from web open source. The blogs are intended only to give technical knowledge to young engineers. Any engineering calculators, technical equations and write ups are only for reference and educational purpose.
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