Cracking The Code
Cracking the Code: ASME B31.3 and Piping Integrity
Steven Fuller – July 2023
Introduction:
Since 1922, the American Society of Mechanical Engineers (ASME) has played a pivotal role in ensuring the safety and reliability of piping systems. Among its notable contributions is the ASME B31.3, a code that sets the standards for piping found in various industries. In this blog post, we will delve into the world of ASME B31.3, exploring its scope, key features, and the vital role it plays in ensuring piping safety. So, let’s embark on a journey through time and innovation!
Defining Piping Safety: ASME B31.3 at a Glance:
ASME B31.3 is a comprehensive code that covers a wide range of piping systems commonly found in petroleum refineries, chemical plants, power generation facilities, and more. It sets forth requirements for materials, components, design, fabrication, assembly, erection, examination, inspection, and testing of piping systems.
Piping in a petrochemical plant.
Fluid Flexibility: ASME B31.3’s Reach:
ASME B31.3 embraces the diverse nature of fluid transport, encompassing a broad range of substances. From raw chemicals to petroleum products, from gas and steam to air and water, and from refrigerants to cryogenic fluids, this code provides guidance on safely handling fluids across various industries. It even extends its coverage to piping that interconnects components within packaged equipment assemblies.
Understanding the Fluid Service Types: A Comprehensive Overview:
ASME B31.3 defines several Fluid Service Categories, each with their own sets of guidelines. Among these Fluid Services are:
Category D Fluid Service: Balancing Safety and Practicality
Category D Fluid Service represents a range of fluids that meet specific safety criteria while remaining practical for general applications. These fluids are non-flammable, non-toxic, and pose no harm to human tissues. With a design pressure not exceeding 150 psi and a temperature range between -29°C and 186°C, Category D encompasses utility lines such as water and air. The preferred materials for this category are carbon steel pipes, including ASTM A53 and API 5L GR B, which may be galvanized or painted.
Category M Fluid Service: Navigating Hazardous Territory
Category M Fluid Service is dedicated to highly toxic substances that require utmost caution and specialized safety measures. Even minimal exposure to these fluids can result in permanent harm. Additionally, if the owner of a facility believes that the safety provisions for normal fluid service are insufficient, the fluid may be categorized as Category M. Designing piping systems for Category M Fluid Service necessitates adherence to the guidelines outlined in Chapter VIII of ASME B31.3, ensuring robust safety measures are in place to mitigate potential risks.
High-Pressure Fluid Service: Withstanding Extraordinary Forces:
High-Pressure Fluid Service encompasses piping systems that must withstand exceptional pressures beyond standard operating conditions. A service is classified as high-pressure when the flange class exceeds 2500. Notably, non-metallic or metallic lined piping components are prohibited in this category. Design and construction requirements for high-pressure fluid service are detailed in Chapter IX of ASME B31.3, emphasizing the need for stringent engineering practices to ensure structural integrity and safety under extreme pressure conditions.
Elevated Temperature Fluid Service: Confronting High-Temperature Challenges:
Elevated Temperature Fluid Service pertains to piping systems that are exposed to sustained high temperatures, requiring special consideration due to the potential impact on material properties. ASME B31.3 defines this service as one in which the metal temperature remains equal to or greater than Tcr, a corrected temperature threshold typically 25°C below the temperature at which time-dependent properties, such as creep, become significant. Designing piping for elevated temperature fluid service demands meticulous evaluation of these mechanical properties to ensure reliable and safe performance under elevated temperature conditions.
High Purity Fluid Service: Upholding Stringent Cleanliness Standards:
High Purity Fluid Service is dedicated to industries that necessitate an exceptionally clean environment to prevent any metal-induced impurities. Industries such as pharmaceuticals and food processing rely on high purity piping systems to maintain stringent hygiene and product integrity standards. ASME B31.3 recognizes the unique requirements of high purity fluid service, which often entail alternative fabrication methods, rigorous inspections, examinations, and specialized testing to achieve and maintain a controlled level of cleanness.
Normal Fluid Service: Versatility and Reliability:
Lastly, we have Normal Fluid Service, the versatile workhorse of piping categories. Any fluid service that does not fit into the specialized categories we discussed earlier falls under this category. It encompasses a wide range of applications and provides the fundamental infrastructure for routine operations in various industries. Whether it’s the transportation of common fluids, gases, or substances, normal fluid service piping plays a vital role in keeping operations running smoothly.
When it comes to design and construction, metallic piping for normal fluid service follows the guidelines outlined in Chapters I to VI of ASME B31.3. This includes considerations for material selection, fabrication, assembly, examination, inspection, and testing. On the other hand, non-metallic and lined piping, which are often utilized in specific applications, have their requirements addressed in Chapter VII of the code. Regardless of the specific materials and configurations employed, normal fluid service piping remains the backbone of countless industrial processes.
ASME B31.3 Guide to Classifying Fluid Services
ASME B31.3 Inspection and Testing:
Below is a table for the base inspection and testing requirements for several fluid services. It’s important to keep in mind that the owner may add additional testing at their discretion.
Ultrasonic testing of a pipe weld.
| Type of Examination | Normal Fluid Service | Category D Fluid Service | Severe Cyclic Conditions | ELEVATED TEMPERATURE FLUID SERVICE |
| Visual – Materials | Sufficient to satisfy examiner. | Sufficient to satisfy examiner. | Sufficient to satisfy examiner. | Sufficient to satisfy examiner. |
| Visual – IN PROCESS Fabrication | 5% at random. | Sufficient to satisfy examiner. | 100% | 100% |
| Visual – Welds | 100% | Sufficient to satisfy examiner. | 100% | 100% |
| Visual – Mechanical | Sufficient to satisfy examiner. | Sufficient to satisfy examiner. | 100% | 100% |
| Visual – Alignment & Supports | Selected at random during erection. | Sufficient to satisfy examiner. | 100% | 100% |
| Visual – Erected piping | Selected at random for defects or deviations. | Sufficient to satisfy examiner. | 100% | 100% |
| NDE – Circumferential Butt and Miter Welds | 5% radiography at random per welder. | Sufficient to satisfy examiner. | 100% radiography. | 5% radiography at random per welder. |
| NDE – Longitudinal and spiral welds | N/A | N/A | N/A | 100% radiography or ultrasonic for P-No. 4 and P-No. 5 materials. |
| NDE – Socket and Branch Connection Welds | N/A | N/A | 100% magnetic particle, or liquid penetrant. | 100% magnetic particle or liquid penetrant for P-No. 4 and P-No. 5 materials. |
| Certifications and Records | Sufficient to satisfy examiner. Certification that all quality requirements of the Code and of the engineering design have been carried out. | Sufficient to satisfy examiner. | Sufficient to satisfy examiner. Certification that all quality requirements of the Code and of the engineering design have been carried out. | Sufficient to satisfy examiner. Certification that all quality requirements of the Code and of the engineering design have been carried out. |
Any additional methods of examination may be specified by the engineering design to supplement the examination required above. The extent of supplementary examination to be performed and any acceptance criteria that differ from those defined in ASME B31.3 shall be specified in the engineering design.
An Essential Companion: ASME B31.3 and the B31 Series:
ASME B31.3 serves as a companion code to ASME’s B31.1 Code on Power Piping and complements other codes within the ASME B31 series. These codes collectively form a comprehensive set of references for professionals involved in piping design, fabrication, and maintenance. They serve as indispensable resources for ensuring compliance with regulations and implementing industry best practices.
Conclusion:
ASME B31.3 stands as a testament to ASME’s commitment to defining and maintaining piping safety standards. With its wide-ranging scope, comprehensive guidelines, and evolutionary updates, this code continues to play a vital role in various industries. Manufacturers, constructors, designers, and governing entities rely on ASME B31.3 to ensure the integrity and reliability of piping systems while reaping the operational, cost, and safety benefits that accompany adherence to industry best practices. As we embrace the future, ASME B31.3 remains a beacon of excellence in the pursuit of piping safety and reliability.