Inspection method of stainless steel elbows

The inspection of stainless steel elbows needs to be carried out from multiple aspects such as appearance, size, material, and performance to ensure that they meet the use requirements and relevant standards (such as GB/T 12459, ASME B16.9, ASTM A403, etc.). The following are detailed inspection methods and steps:

I. Appearance inspection

1. Surface quality

Visual inspection: The surface should be smooth and free of cracks, scratches, oxide scale, depressions, pores, slag inclusions and other defects.

Weld inspection: The weld of the welded elbow should be uniform, without incomplete penetration, undercut or weld nodules.

Polishing: The elbows used in the food or pharmaceutical industry need to check whether the surface polishing reaches Ra≤0.8μm (such as electrolytic polishing or mechanical polishing).

2. Label inspection

Check whether the product label (such as material brand, specification, pressure level, standard number, production batch number, etc.) is clear and complete.

2. Dimension inspection

1. Key dimension measurement

Diameter (DN): Use a vernier caliper or an inside micrometer to measure whether the inside diameter meets the tolerance (usually ±1%).

Wall thickness: Ultrasonic thickness gauge detects the uniformity of wall thickness, and the allowable deviation refers to the standard (such as ±12.5%).

Bending angle and radius: An angle gauge or projector detects whether the bending angle (90°, 45°, etc.) and bending radius meet the requirements of the drawing.

2. End processing

Whether the groove angle and blunt edge size are consistent with the standard (such as welding groove angle 30°~35°).

3. Material verification

1. Chemical composition analysis

Use a spectrometer (such as OES) to detect the material composition (such as whether the Cr, Ni, and Mo content of 304/316 stainless steel meets ASTM A276/A479).

2. Mechanical property test

Tensile test: Detect tensile strength, yield strength, and elongation (such as 304 stainless steel needs to meet ≥515MPa tensile strength).

Hardness test: Brinell hardness (HB) or Rockwell hardness (HRB) test to see if it meets the standard.

IV. Performance test

1. Pressure test

Water pressure test: Fill with water and pressurize to 1.5 times the working pressure, maintain pressure for 10 minutes, no leakage or deformation.

Air pressure test: Applicable to special working conditions, safe operation according to standards.

2. Corrosion resistance test

Salt spray test (ASTM B117): Detect the pitting resistance of materials such as 316L (such as no rust for 48 hours).

Intergranular corrosion test (ASTM A262): Verify whether the material has intergranular corrosion tendency due to improper heat treatment.

3. Nondestructive testing (NDT)

Penetrant testing (PT): Check for tiny cracks on the surface.

Ultrasonic testing (UT): Detect internal pores, inclusions and other defects.

Radiographic testing (RT): X-ray or gamma-ray flaw detection of welds (assessed according to ASME BPVC standards).

V. Additional inspection for special application scenarios

1. Food/pharmaceutical grade elbows

Cleanliness test: Check whether the surface residues (such as grease, particles) meet FDA or GMP standards.

Passivation treatment: Verify the integrity of the passivation film on the stainless steel surface through the blue dot test.

2. High temperature/high pressure working conditions

Metallographic analysis: Observe whether the microstructure is uniform (avoid σ phase embrittlement).

Stress corrosion test: Simulate the stress corrosion resistance under working conditions.

VI. Documents and certifications

1. Quality certification documents

Check whether the material report (MTC), test report (such as UT/RT report), and certificate of conformity meet the procurement requirements.

2. Third-party certification

If CE, PED, API and other certifications are required, the validity of the certificate must be verified.

VII. Common non-conforming items and treatment

Dimensional tolerance: rework or scrap.

Weld defects: retest after repair welding.

Material mismatch: return the entire batch.

Pressure failure: analyze the cause (such as insufficient wall thickness, material defects) and trace the responsibility.

Notes

1. Before inspection, the product implementation standards (such as national standards, American standards, Japanese standards, etc.) must be clarified.

2. For critical occasions (such as nuclear power and chemical industry), it is recommended to entrust a third-party laboratory to conduct full-item testing.

3. Keep inspection records for quality traceability.

Through a systematic inspection process, the reliability and safety of stainless steel elbows can be effectively guaranteed. If further operation details or standard references are required, please provide specific application scenarios!

Cangzhou Aosendik Pipe Fittings Manufacturing Co., Ltd. is a large manufacturer specializing in the production of elbows, tees, reducers, elbows and caps. We can implement ASTM, ANSI, JIS, DIN, GB and other standards, basically covering all types of steel.

If you have any purchasing needs or questions, please contact us.

Mobile: 86-13668807131

Website: https://www.authenticfitting.com/

Address: Mengcun Hui Autonomous County, Cangzhou City, Hebei Province

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