Stainless steel pipe fittings are a type of pipe fittings. They are made of stainless steel and include: stainless steel elbows, stainless steel tees, stainless steel crosses, stainless steel reducers, stainless steel caps, etc. Their connection methods can be divided into four categories: socket-type stainless steel pipe fittings, threaded stainless steel pipe fittings, flanged stainless steel pipe fittings and welded stainless steel pipe fittings.

Main materials of stainless steel pipe fittings: 304, 304L, 316|, 316L

1. Inspection of geometric dimensions and appearance of stainless steel pipes:

① Inspection of stainless steel pipe wall thickness: micrometer, ultrasonic thickness gauge, no less than 8 points at both ends and record.

② Inspection of stainless steel pipe outer diameter and ovality: caliper, vernier caliper, ring gauge, measure the maximum point and minimum point.

③ Inspection of stainless steel pipe length: steel tape measure, manual and automatic length measurement.

④ Inspection of stainless steel pipe curvature: ruler, level ruler (1m), feeler gauge, fine wire to measure curvature per meter and full length curvature.

⑤ Check the bevel angle and blunt edge of the stainless steel pipe end face: angle ruler, card plate.

2. Surface quality inspection of stainless steel pipe: 100%

① Manual visual inspection: lighting conditions, standards, experience, marking, stainless steel pipe rotation.

② Nondestructive testing:

a. Ultrasonic flaw detection UT:

It is sensitive to surface and internal crack defects of uniform materials of various materials.

Standard: GB/T 5777-1996 Level: C5

b. Eddy current flaw detection ET: (electromagnetic induction)

It is mainly sensitive to point-shaped (hole-shaped) defects. Standard: GB/T 7735-2004

Level: B

c. Magnetic powder MT and magnetic leakage flaw detection:

Magnetic flaw detection is suitable for the detection of surface and near-surface defects of ferromagnetic materials.

Standard: GB/T 12606-1999 Level: C4

d. Electromagnetic ultrasonic flaw detection:

No coupling medium is required, and it can be applied to high-temperature, high-speed, rough stainless steel pipe surface flaw detection.

e. Penetrant flaw detection:

Fluorescence, coloring, detection of stainless steel pipe surface defects.

III. Stainless steel management performance inspection

① Tensile test: measure stress and deformation, determine the strength (YS, TS) and plasticity index (A, Z) of the material

Longitudinal, transverse sample pipe sections, arc-shaped, circular samples (￠10, ￠12.5)

Small diameter, thin wall, large diameter, thick wall calibration distance

Note: The elongation after fracture of the sample is related to the size of the sample GB/T 1760

② Impact test: CVN, notch C type, V type, work J value J/cm2

Standard sample 10×10×55 (mm) Non-standard sample 5×10×55 (mm)

③ Hardness test: Brinell hardness HB, Rockwell hardness HRC, Vickers hardness HV, etc.

④ Hydraulic test: test pressure, stabilization time, p=2Sδ/D

IV. Process performance inspection of stainless steel pipes

① Flattening test: round sample C-shaped sample (S/D＞0.15) H=（1+2）S/（∝+S/D）

L=40～100mm Unit length deformation coefficient = 0.07～0.08

② Ring pull test: L=15mm Qualified if there is no crack

③Expansion and curling test: the top taper is 30°, 40°, 60°

④Bending test: can replace the flattening test (for large diameter pipes)