Nondestructive testing (NDT) is a type of testing that is used to evaluate the properties of a material, component, or system without causing damage or destruction. NDT methods are used in a variety of industries, including manufacturing, construction, and aviation, to ensure the quality and integrity of materials and components.
- Visual inspection: Defects such as cracks, porosity, and incomplete fusion must not be visible.
- Dye penetrant inspection: The dye must not penetrate into any surface defects.
- Magnetic particle inspection: There must not be any visible indications of surface defects.
- Ultrasonic testing: The weld must be free of defects that are detectable by the specific ultrasonic testing method being used.
- Radiographic testing: The weld must be free of defects that are detectable by the specific radiographic testing method being used.
It is important to follow the specific acceptance standards and procedures outlined in API 1104 for the NDT of production welds. These standards are designed to ensure the quality and integrity of the welded joints being tested.
Radiographic Testing (API 1104)
Radiographic testing (RT) is a nondestructive testing method that uses X-rays or gamma rays to inspect the internal structure of a welded joint. It is commonly used to detect defects such as cracks, porosity, and incomplete fusion that are not visible to the naked eye.
To perform radiographic testing, a source of X-rays or gamma rays is positioned on one side of the welded joint and a film or detector is positioned on the other side. The rays pass through the weld and any defects will be visible on the film or detector as dark or light areas.
For example, consider a welded joint that is being inspected using radiographic testing. If the weld is free of defects, the X-rays or gamma rays will pass through the weld without being absorbed and the film or detector will show a uniform image. If there is a defect in the weld, such as a crack, the rays will be absorbed by the defect and the film or detector will show a dark area at the location of the defect. This indicates that there is a problem with the weld and it may need to be repaired or rejected.
Magnetic Particle Testing (API 1104)
Magnetic particle testing (MT) is a nondestructive testing method that uses a magnetic field to detect surface and slightly subsurface defects in ferromagnetic materials, such as steel. It is commonly used to detect cracks, seams, laps, and other surface defects in welds.
To perform magnetic particle testing, a magnetic field is applied to the surface of the welded joint. Iron oxide or iron oxide-coated plastic particles are then sprinkled over the surface of the weld. If there are any surface defects, such as cracks, the particles will be attracted to the defect and be visible on the surface of the weld.
For example, consider a welded joint that is being inspected using magnetic particle testing. If the weld is free of defects, the magnetic field will not cause any of the iron oxide particles to be attracted to the surface of the weld. If there is a defect in the weld, such as a crack, the magnetic field will cause the iron oxide particles to be attracted to the defect and be visible on the surface of the weld. This indicates that there is a problem with the weld and it may need to be repaired or rejected.
Liquid Penetrant Testing (API 1104)
Liquid penetrant testing (PT) is a nondestructive testing method that uses a liquid dye to detect surface defects in nonporous materials, such as metals. It is commonly used to detect cracks, seams, laps, and other surface defects in welds.
To perform liquid penetrant testing, a liquid dye is applied to the surface of the welded joint. The dye is allowed to penetrate into any surface defects for a specified amount of time, and then the excess dye is removed. A developer solution is then applied to the surface of the weld. Any surface defects that allowed the dye to penetrate will be visible as a colored indication on the surface of the weld when the developer solution is applied.
For example, consider a welded joint that is being inspected using liquid penetrant testing. If the weld is free of defects, the dye will not penetrate into the surface of the weld and no colored indications will be visible when the developer solution is applied. If there is a defect in the weld, such as a crack, the dye will penetrate into the defect and a colored indication will be visible on the surface of the weld when the developer solution is applied. This indicates that there is a problem with the weld and it may need to be repaired or rejected.
Ultrasonic Testing (API 1104)
Ultrasonic testing (UT) is a nondestructive testing method that uses high-frequency sound waves to detect defects in materials, such as welds. It is commonly used to detect cracks, porosity, and other internal defects that are not visible to the naked eye.
To perform ultrasonic testing, a probe is placed on the surface of the welded joint and high-frequency sound waves are transmitted through the weld. Any defects in the weld will cause reflections or echoes of the sound waves, which can be detected and analyzed by the probe.
For example, consider a welded joint that is being inspected using ultrasonic testing. If the weld is free of defects, the sound waves will pass through the weld without being reflected and no echoes will be detected by the probe. If there is a defect in the weld, such as a crack, the sound waves will be reflected by the defect and an echo will be detected by the probe. This indicates that there is a problem with the weld and it may need to be repaired or rejected.
Following is API 1104 Reference document.
Acceptance-Standards-for-Nondestructive-Testing-1Welding of Pipelines and Related Facilities According to API 1104
References and Intranational Standard used in API 1104
DEFINITION OF TERMS USED IN API 1104
QUALIFICATION OF WELDING PROCEDURES FOR WELDS CONTAINING FILLER-METAL ADDITIVES
DESIGN AND PREPARATION OF A JOINT FOR PRODUCTION WELDING
INSPECTION AND TESTING OF PRODUCTION WELDS
ACCEPTANCE STANDARDS FOR NONDESTRUCTIVE TESTING
AUTOMATIC WELDING WITHOUT FILLER-METAL ADDITIONS