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Quality Inspection Measures for Stainless Steel Elbow Welding

Jul. 23, 2020

Elbow Fitting Supplier shares this article for you.

In piping systems, elbows are pipe fittings that change the direction of the pipe. According to the angle of the elbow, the most commonly used elbows are 45°, 90°, and 180°. Other abnormal bend angles (such as 60°) can also be included according to engineering needs.

Stainless steel elbow welding quality inspection method

1. Non-destructive testing

Detect defects such as inclusions, pores, and cracks in the weld. At present, X-ray inspection, ultrasonic inspection and magnetic inspection are the most commonly used. X-ray inspection is the use of X-ray photography technology of welds to determine whether there are defects, how many defects and types are based on the image of the negative.

Then evaluate whether the weld is qualified according to the technical requirements of the product. The basic principle of ultrasonic flaw detection is that the probe sends out ultrasonic flaw detection and transmits it to the metal. When ultrasonic waves are transmitted to the interface between metal and air, it refracts and passes through the weld.

If the weld is defective, the ultrasonic wave will be reflected on the probe and be accepted, and the reflected wave will appear on the screen. By comparing and identifying these reflected waves and ordinary waves, the size and location of the defect can be determined. Ultrasonic inspection is much simpler than X-ray inspection, so it has been widely used

However, ultrasonic flaw detection can only be judged based on operating experience and cannot leave a basis for inspection. Magnetic force can also be used to detect internal defects and small cracks on the weld surface.

Welded Elbow

Welded Elbow

2. Visual inspection

Generally observe with naked eyes, sometimes with 5-20 times magnifying glass. Through visual inspection, it is possible to find defects on the weld surface of the welded elbow, such as undercuts, weld bead, surface cracks, pores, slag inclusions, and weld penetration.

The shape and size of the weld can also be measured with a weld joint detector or template.

3. Mechanical performance test of elbow

Non-destructive testing can find defects in the weld, but cannot explain the mechanical properties of the metal in the heat-affected zone of the weld. Sometimes it is necessary to perform tensile, impact, and bending tests on the welded joint.

These tests are carried out by test panels. The test plate is best to be welded to the longitudinal joint of the cylinder to ensure consistent construction conditions. Then test the mechanical properties of the test board. In actual production, only the welded joints of New Steel are tested in this area.

4. Water pressure test and air pressure test

For pressure vessels that need to be sealed, water pressure test and/or air pressure test must be carried out to check the sealing and pressure bearing capacity of the weld.

The method is to inject clean water or gas equivalent to the working pressure (mainly air) 1.25 to 1.5 times the working pressure of the container, stay for a period of time, then observe the pressure drop in the container, and observe the external leakage phenomenon, which can be assessed Whether the weld is qualified.