ASME B31T

ASME B31T

Standard Toughness Requirements for Piping
Standard Toughness Requirements for Piping

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Scope:
INTRODUCTION

This Code provides requirements for evaluating the suitability of materials used in piping systems for piping that may be subject to brittle failure due to lowtemperature service conditions. While low-temperature service is usually considered to be below ambient temperature, brittle failure can occur at temperatures above ambient temperature for certain combinations of materials, thicknesses, and stress levels. The definition of “lowtemperature service” as used in this Code, therefore, varies widely across the many applications for which piping systems are used. For a building service air line, low temperature may be 0°C (32°F), whereas for a cryogenic piping system, it could easily be −185°C (−300°F).1 However, the principles used to evaluate the suitability of a piping system as related to service temperature by evaluating the toughness of the material can be applied across a wide temperature range, and this Code has been established to provide uniform guidance in this area. This Code may be invoked in whole or in part by various piping codes and/or specifications and is only mandatory when so invoked.

Suitability of piping systems for low-temperature service is a function of several variables, including material properties, design loadings, and fabrication procedures. The three primary factors that generally control the susceptibility for brittle fracture are material toughness, crack size, and tensile stress level. There are a wide variety of services where low-temperature suitability need not even be considered; however, a screening criterion is necessary to determine this.

One objective of this Code is to provide a simple approach to evaluate whether additional consideration is necessary to evaluate suitability for low-temperature service. This is done by establishing a low-temperature service limit for various materials. Services at or warmer than this limit are not considered low temperature, and additional considerations relative to suitability are not required.

For services colder than this limit, various requirements are provided that, when met, qualify the material for low-temperature services. These requirements include impact testing, qualification of welding and other fabrication procedures, and limiting the design loadings.

The low-temperature service limit established herein is based on a reasonable degree of assurance that at this temperature the material will have a ductile failure mode. The actual ductile-to-brittle transition temperature for a given material specification will vary based on actual heat chemistry of the material and subsequent processing. For critical applications, the design engineer can select materials with a lower low-temperature service limit, or require impact testing. On less-critical applications, material with a higher low-temperature service limit may be acceptable. The final selection is left to the referring code and the design engineer (when permitted by the referring code).

To keep the number of sets of requirements to a minimum, material groupings have been established, and a unique set of requirements have been provided for each group. These groups are assigned “T-numbers” for easy reference. Although most materials used in piping systems are listed, some are not, and these unlisted materials are not addressed in this Code. Where permitted by code or specification invoking this Code, these requirements may be used for unlisted materials. The invoking code or specification may establish the correct T-number group for the material or may invoke the testing and other requirements of this Code using the worst-case assumption that the design minimum temperature is colder than the temperatures that would allow exemption from any of the requirements of this Code. The guidelines for establishing the correct T-number group are provided in Nonmandatory Appendix B.

1 For guidance on cryogenic valves, refer to MSS SP-134, Valves for Cryogenic Service Including Requirements for Body/Bonnet Extensions.

NASA Lessons:
This lesson addresses a catastrophic failure of a high pressure (225 psig) steam line strainer largely due to inappropriate use of material and the violation of the maximum allowance stress for the cast iron strainer per ASME B31.1. This lesson is relevant to paragraphs 122.3.1, 122.7.4, and 124.6 of this ASME Prssure Piping code
Organization: ASME International
Document Number: asme b31t
Publish Date: 2015-01-01
Page Count: 54
Change Type: COMPLETE REVISION
Available Languages: EN
DOD Adopted: NO
ANSI Approved: NO
Most Recent Revision: YES
Current Version: YES
Status: Active

Publication Date: 01/01/2015 - Complete Document

Description :

INTRODUCTION

This Code provides requirements for evaluating the suitability of materials used in piping systems for piping that may be subject to brittle failure due to lowtemperature service conditions. While low-temperature service is usually considered to be below ambient temperature, brittle failure can occur at temperatures above ambient temperature for certain combinations of materials, thicknesses, and stress levels. The definition of “lowtemperature service” as used in this Code, therefore, varies widely across the many applications for which piping systems are used. For a building service air line, low temperature may be 0°C (32°F), whereas for a cryogenic piping system, it could easily be −185°C (−300°F).1 However, the principles used to evaluate the suitability of a piping system as related to service temperature by evaluating the toughness of the material can be applied across a wide temperature range, and this Code has been established to provide uniform guidance in this area. This Code may be invoked in whole or in part by various piping codes and/or specifications and is only mandatory when so invoked.

Suitability of piping systems for low-temperature service is a function of several variables, including material properties, design loadings, and fabrication procedures. The three primary factors that generally control the susceptibility for brittle fracture are material toughness, crack size, and tensile stress level. There are a wide variety of services where low-temperature suitability need not even be considered; however, a screening criterion is necessary to determine this.

One objective of this Code is to provide a simple approach to evaluate whether additional consideration is necessary to evaluate suitability for low-temperature service. This is done by establishing a low-temperature service limit for various materials. Services at or warmer than this limit are not considered low temperature, and additional considerations relative to suitability are not required.

For services colder than this limit, various requirements are provided that, when met, qualify the material for low-temperature services. These requirements include impact testing, qualification of welding and other fabrication procedures, and limiting the design loadings.

The low-temperature service limit established herein is based on a reasonable degree of assurance that at this temperature the material will have a ductile failure mode. The actual ductile-to-brittle transition temperature for a given material specification will vary based on actual heat chemistry of the material and subsequent processing. For critical applications, the design engineer can select materials with a lower low-temperature service limit, or require impact testing. On less-critical applications, material with a higher low-temperature service limit may be acceptable. The final selection is left to the referring code and the design engineer (when permitted by the referring code).

To keep the number of sets of requirements to a minimum, material groupings have been established, and a unique set of requirements have been provided for each group. These groups are assigned “T-numbers” for easy reference. Although most materials used in piping systems are listed, some are not, and these unlisted materials are not addressed in this Code. Where permitted by code or specification invoking this Code, these requirements may be used for unlisted materials. The invoking code or specification may establish the correct T-number group for the material or may invoke the testing and other requirements of this Code using the worst-case assumption that the design minimum temperature is colder than the temperatures that would allow exemption from any of the requirements of this Code. The guidelines for establishing the correct T-number group are provided in Nonmandatory Appendix B.

1 For guidance on cryogenic valves, refer to MSS SP-134, Valves for Cryogenic Service Including Requirements for Body/Bonnet Extensions.

Document Type : Complete Document

Language : English

Page Count : 54

Publication Date : 01/01/2015

Revision : 15

Status : Current

Title : Standard Toughness Requirements for Piping

Publication Date: 06/01/2010 - Complete Document

Description :

INTRODUCTION

This Standard provides requirements for evaluating the suitability of materials used in piping systems for piping that may be subject to brittle failure due to lowtemperature service conditions. While low-temperature service is usually considered to be below ambient temperature, brittle failure can occur at temperatures above ambient temperature for certain combinations of materials, thicknesses, and stress levels. The definition of "lowtemperature service" as used in this Standard, therefore, varies widely across the many applications for which piping systems are utilized. For a building service air line, low temperature may be 0°C (32°F), whereas for a cryogenic piping system, it could easily be −185°C (−300°F). However, the principles used to evaluate the suitability of a piping system as related to service temperature by evaluating the toughness of the material can be applied across a wide temperature range, and this Standard has been established to provide uniform guidance in this area. This Standard may be invoked in whole or in part by various piping codes and/or specifications and is only mandatory when so invoked.

Suitability of piping systems for low-temperature service is a function of several variables, including material properties, design loadings, and fabrication procedures. The three primary factors that generally control the susceptibility for brittle fracture are material toughness, crack size, and tensile stress level. There are a wide variety of services where low-temperature suitability need not even be considered; however, a screening criterion is necessary to determine this.

One objective of this Standard is to provide a simple approach to evaluate whether additional consideration is necessary to evaluate suitability for low-temperature service. This is done by establishing a low-temperature service limit for various materials. Services at or warmer than this limit are not considered low temperature, and additional considerations relative to suitability are not required.

For services colder than this limit, various requirements are provided that, when met, qualify the material for low-temperature services. These requirements include impact testing, qualification of welding and other fabrication procedures, and limiting the design loadings.

The low-temperature service limit established herein is based on a reasonable degree of assurance that at this temperature the material will have a ductile failure 1 mode. The actual ductile-to-brittle transition temperature for a given material specification will vary based on actual heat chemistry of the material and subsequent processing. For critical applications, the design engineer can select materials with a lower low-temperature service limit, or require impact testing. On less critical applications, material with a higher low-temperature service limit may be acceptable. The final selection is left to the referring code and the design engineer (when permitted by the referring code).

To keep the number of sets of requirements to a minimum, material groupings have been established, and a unique set of requirements have been provided for each group. These groups are assigned "T-Numbers" for easy reference. Although most materials utilized in piping systems are listed, some are not, and these unlisted materials are not addressed in this Standard. Where permitted by code or specification invoking this Standard, these requirements may be utilized for unlisted materials. The invoking code or specification may establish the correct T-Number group for the material or may invoke the testing and other requirements of this Standard utilizing the worst case assumption that the design minimum temperature is colder than the temperatures that would allow exemption from any of the requirements of this Standard. The guidelines for establishing the correct T-Number group are provided in Nonmandatory Appendix B.

Document Type : Complete Document

Language : English

Page Count : 52

Publication Date : 06/01/2010

Revision : 10

Status : Historical

Title : Standard Toughness Requirements for Piping

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