Quality inspection method of SSAW steel pipe

Ensuring the quality of spiral steel pipes (SSAW) is crucial for their reliable performance in various applications. The following methods are employed to inspect the quality of SSAW steel pipes.

Visual Inspection:

This involves examining the surface of the welded joints to identify any visible defects. It is a straightforward yet essential procedure that helps detect surface imperfections and dimensional deviations. Tools such as standard models, gauges, and magnifying glasses are often used in conjunction with the naked eye to carry out this inspection. Surface flaws detected through visual inspection can indicate potential internal defects in the weld.

Physical Inspection Methods:

These methods utilize physical phenomena to inspect or test the materials. Non-destructive testing (NDT) techniques, such as X-ray flaw detection, are commonly used to inspect the internal defects of materials or parts. X-ray inspection provides objective, real-time imaging, allowing software to automatically identify, locate, and measure defects.

Strength Testing for Pressure Vessels:

Pressure vessels undergo strength testing to ensure their weld density. This can be done using hydraulic or pneumatic tests. Hydraulic testing is typically slower and requires draining the tested product, whereas pneumatic testing is faster and more sensitive but carries a higher risk. Safety and technical measures must be strictly observed during pneumatic testing to prevent accidents.

Compaction Test:

This test checks for non-dense defects such as penetrating cracks, pores, slag, and loose organization in welded containers storing liquid or gas. Common methods include kerosene tests, water tests, and other similar procedures.

Hydrostatic Pressure Test:

Each steel pipe undergoes a hydrostatic test to ensure there are no leaks. The test pressure is determined using the formula P = 2ST / D, where S is the hydrostatic test pressure in Mpa, T is the wall thickness, and D is the pipe diameter. The duration of the test pressure varies with the pipe size: pipes with D < 508 mm are tested for at least 5 seconds, while those with D ≥ 508 mm are tested for at least 10 seconds.

Non-Destructive Testing (NDT):

This involves the use of X-ray or ultrasonic testing for inspecting the welds of structural steel pipes, steel head welds, and ring joints. For pipes transporting flammable fluids, 100% of the spiral welds undergo X-ray or ultrasonic testing. Pipes carrying general fluids like water, sewage, air, and heating steam are also inspected using these methods. X-ray inspection is particularly advantageous due to its objective imaging, lower professional requirements, and the ability to store and trace data.