What is the testing method for butter weld elbow after corrosion
Butt weld elbows may suffer from corrosion if used improperly. Once corroded, they typically exhibit symptoms such as wall thinning, local pitting, and pit formation.
The magnetic flux leakage method, used to detect corrosion in butt weld elbows, operates on the principle of the high magnetic permeability of ferromagnetic materials. The magnetic permeability at corrosion-induced defects in butt weld elbows is significantly lower than that of the intact elbow. When the elbow is magnetized by an external magnetic field, most magnetic lines of force pass through the steel pipe in a uniform distribution if there are no defects. However, in the presence of internal defects, the magnetic lines of force will bend, with some leaking out of the steel pipe surface. By detecting such leaked magnetic flux from the surface of the magnetized elbow, the presence of defects can be identified.
The ultrasonic testing method utilizes the pulse reflection principle of ultrasonic waves to measure the wall thickness of corroded elbows. During inspection, a probe emits ultrasonic pulses vertically toward the inner wall of the welded elbow. The probe first receives reflected pulses from the inner surface of the pipe wall, followed by those from the outer surface. The interval between these two sets of pulses (relative to the inner surface reflections) indicates the actual wall thickness.
Additional notes on processing:
- Bending: The process of forming butt weld elbows from pipes, typically applied to metal pipes and electrical PVC conduits used in water and electricity industries.
- Bent welded elbows: Primarily refer to metal welded elbows in water supply and drainage systems. Small-diameter welded elbows can be produced through bending processes.