Methodology is one of the important thing that we have to know in Piping and Fabrication Systems. There is so many thing and knowledge that we can read here only on Piping & Fabrication.
The ASME Boiler and Pressure Vessel, B31.1 and B31.3, require certain NDEs to be performed in accordance with the methods described in ASME Section V Nondestructive Examination. The pipeline codes, B31.4, B31.8, and B31.11, refer to API-1104 for Radiographic Procedures. In some cases, particularly in visual examination, requirements are given but no specific methodology is stated. In others, alternative parameters or qualification requirements are given. The specific requirements of the individual codes should be consulted.
Qualification Requirements. Qualification of procedures and personnel used in NDEs are required by most codes. When ASME Section V orAPI-1104 are invoked by the referencing code, a written procedure is required and it must be demonstrated to the satisfaction of the AI, ANI, owner, or owner’s agent, whichever is applicable.
Similarly personnel who perform NDEs must be trained, qualified, and certified. The most frequently invoked qualification document is SNT-TC-1A; it is also accepted by B31.1 for qualification of personnel performing visual examinations. Some codes permit alternatives, such as AWS-QC-1
Table A
Acceptance Standards for Visual Examination
The following indications are unacceptable:
1. Crack(s) on external surfaces
2. Undercut on surface greater than 1⁄32 in (1.0 mm) deep
3. Weld reinforcement greater than specified in ASME Table 127.4.2
4. Lack of fusion on surface
5. Incomplete penetration (applies only when inside surface is readily accessible)
6. Any other linear indications greater than 3⁄₁₆ in (5.0 mm) long
7. Surface porosity with rounded indications having dimensions greater than 3⁄16 in (5.0 mm) or 4 or more rounded indications separated by 1⁄16 in (2.0 mm) or less edge to edge in any direction. Rounded indications are indications which are circular or elliptical with their length less than 3 times their width
Source: From ASME B31.1 1995 ed.
Extent of Examination. The applicable code will define the extent of examination required for piping systems under its coverage. The degree of examination and the examination method and alternatives are a function of the degree of hazard which might be expected to occur in the event of failure. Pressure, temperature, toxicity of the fluid, and release of radioactive substances are some of the considerations. Added layers of examinations may be required as the perceived hazard increases.
Accept-Reject Criteria. The applicable code will also define the items to be examined and the accept-reject criteria to be applied. Table A shows the acceptance standards applicable to the visual examination of butt welds under B31.1. Other piping codes have similar but not necessarily identical criteria.
Table B shows acceptance standards for radiographic examination. Indications interpreted as cracks, incomplete penetration, or lack of fusion are not permitted. Porosity and elongated indications are kept within certain limits. The acceptance standards for ultrasonic examination are similar.
Table B
Acceptance Standards for Radiography
Welds that are shown by radiography to have any of the following types of discontinuities are unacceptable:
1. Any type of crack or zone of incomplete fusion or penetration
2. Any other elongated indication with a length greater than
a. 1⁄4 in (6.0 mm) for t up to 3⁄₄ in (19.0 mm)
b. 1⁄3 t for t from 3⁄4 in (6.0 mm) to 21⁄4 in (57.0 mm) inclusive
c. 3⁄4 in (19.0 mm) for t over 21⁄4 in (57.0 mm) where t is the thickness of the thinner portion of the weld
3. Any group of indications in a line that have an aggregate length greater than t in a length of 12 t, except where the distance between successive indications exceeds 6L where L is the longest indication in the group
4. Porosity in excess of that shown as acceptable in Appendix A-250 of Section I of the Boiler and Pressure Vessel Code
5. Root concavity when there is an abrupt change in density indicated on the radiograph
Table C
Acceptance Standards for Magnetic Particle and Liquid Penetrant Examinations
The following relevant indications are unacceptable:
1. Any cracks or linear indications
2. Rounded indications with dimensions greater than 3⁄16 in (5.0 mm)
3. Four or more rounded indications in a line separated by 1⁄16 in (2.0 mm) or less edge
to edge
4. Ten or more rounded indications in any 6 in2 (3870 mm2) of surface with the major dimension of this surface not to exceed 6 in (150 mm) with the area taken in the most unfavorable location relative to the indications being evaluated
Both magnetic particle and liquid penetrant examinations have identical limits. See Table C, Other types of NDEs, such as acoustic emission, bubble testing, and mass spectrometer testing, are not required by the various codes. They can be invoked by contract and the acceptance standards must be a matter of agreement between the contracting parties.
Testing. All of the piping codes outline some type of pressure test to determine leak tightness. Since the completed piping system is usually subjected to some type of test in the field after installation, shop testing of subassemblies is infrequent. In those cases where the assembly cannot be field tested, where welds in the assembly will not be exposed for examination during the field test, and in other special situations, shop testing may be required. Shop testing must meet all of the requirements for field testing. See the section ‘‘Installation’’ for particulars.
Quality Assurance and Quality Control. ASME Section III has very specific requirements for QA programs. ASME Section I has requirements for QC programs. The B31 Piping Codes do not require any formal written program at this time. Refer to these codes for detailed information on this subject.
The ASME Boiler and Pressure Vessel, B31.1 and B31.3, require certain NDEs to be performed in accordance with the methods described in ASME Section V Nondestructive Examination. The pipeline codes, B31.4, B31.8, and B31.11, refer to API-1104 for Radiographic Procedures. In some cases, particularly in visual examination, requirements are given but no specific methodology is stated. In others, alternative parameters or qualification requirements are given. The specific requirements of the individual codes should be consulted.
Qualification Requirements. Qualification of procedures and personnel used in NDEs are required by most codes. When ASME Section V orAPI-1104 are invoked by the referencing code, a written procedure is required and it must be demonstrated to the satisfaction of the AI, ANI, owner, or owner’s agent, whichever is applicable.
Similarly personnel who perform NDEs must be trained, qualified, and certified. The most frequently invoked qualification document is SNT-TC-1A; it is also accepted by B31.1 for qualification of personnel performing visual examinations. Some codes permit alternatives, such as AWS-QC-1
Table A
Acceptance Standards for Visual Examination
The following indications are unacceptable:
1. Crack(s) on external surfaces
2. Undercut on surface greater than 1⁄32 in (1.0 mm) deep
3. Weld reinforcement greater than specified in ASME Table 127.4.2
4. Lack of fusion on surface
5. Incomplete penetration (applies only when inside surface is readily accessible)
6. Any other linear indications greater than 3⁄₁₆ in (5.0 mm) long
7. Surface porosity with rounded indications having dimensions greater than 3⁄16 in (5.0 mm) or 4 or more rounded indications separated by 1⁄16 in (2.0 mm) or less edge to edge in any direction. Rounded indications are indications which are circular or elliptical with their length less than 3 times their width
Source: From ASME B31.1 1995 ed.
Extent of Examination. The applicable code will define the extent of examination required for piping systems under its coverage. The degree of examination and the examination method and alternatives are a function of the degree of hazard which might be expected to occur in the event of failure. Pressure, temperature, toxicity of the fluid, and release of radioactive substances are some of the considerations. Added layers of examinations may be required as the perceived hazard increases.
Accept-Reject Criteria. The applicable code will also define the items to be examined and the accept-reject criteria to be applied. Table A shows the acceptance standards applicable to the visual examination of butt welds under B31.1. Other piping codes have similar but not necessarily identical criteria.
Table B shows acceptance standards for radiographic examination. Indications interpreted as cracks, incomplete penetration, or lack of fusion are not permitted. Porosity and elongated indications are kept within certain limits. The acceptance standards for ultrasonic examination are similar.
Table B
Acceptance Standards for Radiography
Welds that are shown by radiography to have any of the following types of discontinuities are unacceptable:
1. Any type of crack or zone of incomplete fusion or penetration
2. Any other elongated indication with a length greater than
a. 1⁄4 in (6.0 mm) for t up to 3⁄₄ in (19.0 mm)
b. 1⁄3 t for t from 3⁄4 in (6.0 mm) to 21⁄4 in (57.0 mm) inclusive
c. 3⁄4 in (19.0 mm) for t over 21⁄4 in (57.0 mm) where t is the thickness of the thinner portion of the weld
3. Any group of indications in a line that have an aggregate length greater than t in a length of 12 t, except where the distance between successive indications exceeds 6L where L is the longest indication in the group
4. Porosity in excess of that shown as acceptable in Appendix A-250 of Section I of the Boiler and Pressure Vessel Code
5. Root concavity when there is an abrupt change in density indicated on the radiograph
Table C
Acceptance Standards for Magnetic Particle and Liquid Penetrant Examinations
The following relevant indications are unacceptable:
1. Any cracks or linear indications
2. Rounded indications with dimensions greater than 3⁄16 in (5.0 mm)
3. Four or more rounded indications in a line separated by 1⁄16 in (2.0 mm) or less edge
to edge
4. Ten or more rounded indications in any 6 in2 (3870 mm2) of surface with the major dimension of this surface not to exceed 6 in (150 mm) with the area taken in the most unfavorable location relative to the indications being evaluated
Both magnetic particle and liquid penetrant examinations have identical limits. See Table C, Other types of NDEs, such as acoustic emission, bubble testing, and mass spectrometer testing, are not required by the various codes. They can be invoked by contract and the acceptance standards must be a matter of agreement between the contracting parties.
Testing. All of the piping codes outline some type of pressure test to determine leak tightness. Since the completed piping system is usually subjected to some type of test in the field after installation, shop testing of subassemblies is infrequent. In those cases where the assembly cannot be field tested, where welds in the assembly will not be exposed for examination during the field test, and in other special situations, shop testing may be required. Shop testing must meet all of the requirements for field testing. See the section ‘‘Installation’’ for particulars.
Quality Assurance and Quality Control. ASME Section III has very specific requirements for QA programs. ASME Section I has requirements for QC programs. The B31 Piping Codes do not require any formal written program at this time. Refer to these codes for detailed information on this subject.
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