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)

1. Grooved pipe fittings are easy to connect The connection operation of stainless steel grooved pipe fittings is very simple, and no special professional skills are required. Ordinary workers can operate it after simple training. This is because the product has incorporated a large number of fine technical parts into the finished product in a factory-based manner. Pipe fitting connection only takes a few minutes, which greatly simplifies the technical difficulty of on-site operation, saves man-hours, and thus stabilizes the quality of the project and improves work efficiency. This is also the overall direction of the development of installation technology. The traditional welding and flange connection pipeline connection methods not only require welding workers with corresponding skills, but are also time-consuming, difficult for workers to operate, and there is pollution from welding smoke. Due to differences in operating space and welding skills, it is difficult to achieve satisfactory results in welding quality and appearance, which affects the overall quality of the project. In addition, since the grooved pipe fittings are finished parts, the operating space required on site is small, and it can be truly installed against the wall and corners, and the difficulty of operation is greatly reduced, thereby saving floor space and beautifying the effect of pipeline installation. 2. Grooved pipe fittings do not require secondary treatment For stainless steel grooved pipe fittings, only a groove is squeezed out of the outer surface of the connected pipe with a groove rolling machine without damaging the inner wall structure of the pipe. This is a unique technical advantage of grooved pipe fittings. If traditional welding operations are used, many pipes with anti-corrosion layers on the inner wall will be damaged. Therefore, the specification stipulates that galvanized pipes, plastic-lined steel pipes, steel-plastic composite pipes, etc. must not be connected by welding and flanges, otherwise secondary treatment is required. 3. Grooved pipe fittings connection construction safety Using grooved pipe fittings connection technology, only cutting machines, groove rolling machines and wrenches for tightening bolts are required on site, which is convenient for construction organization. However, welding and flange connections require complex power cables, cutting machines, welding machines, oxygen and acetylene cylinders, etc., which brings complexity to the construction organization and also poses a risk of leakage and fire. At the same time, the welding slag produced by welding and gas cutting will inevitably fall into the interior of the pipeline, which is easy to cause pipeline valves and even equipment blockage during use, and also pollute the water quality in the pipe. In addition, welding and flange connection inevitably require long-term high-intensity high-altitude operations, and are prone to production safety accidents. 4. Grooved pipe fittings are easy to maintain The stainless steel grooved pipe fitting connection method has unique flexibility, which makes the pipeline anti-vibration, anti-contraction and anti-expansion. Compared with welding and flange connection, the stability of the pipeline system is increased, which is more suitable for temperature changes, thereby protecting the pipeline valve and reducing the damage of pipeline stress to structural parts. Because the grooved pipe fitting connection operation is simple and the required operating space is smaller, it brings many convenient conditions for future maintenance. When the pipeline needs to be repaired and replaced, just loosen the two clamps to replace, rotate and modify a section of the pipeline at will. There is no need to damage the surrounding walls, which reduces maintenance time and maintenance costs.