How can one determine the quality of these three flanges?
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Third-tier cities in Guangdong (virtually equivalent to fourth-tier cities: L); the stainless steel flanges supplied by local vendors are of DN50 size, and those that meet national standards are of this type – only this standard and the 20592 standard are available. The thickness of the flanges with bosses is 13–14 mm; it is said that **standard ones are not in stock, only these are available**. The local suppliers are all from Fujian; do they look like products from Putian? Wenzhou goods. . . Although the operational requirements are not high, with pipeline pressures generally below 0.5 MPa, this looks really poor quality. . . How do I determine which one of the three is a bit better?
Are flange standards no longer in use, yet are they still being produced?
Lots. . . This is the type of product found almost everywhere in the city. There aren’t many petrochemical companies locally, but there are quite a number of fine chemical enterprises. They are all small factories
Acceptance is carried out in accordance with the standards you require or the supplier’s standards: acceptance of dimensions, and acceptance of the material (through spectroscopy to check whether the content of alloying elements is within acceptable limits)
Just looking at the color and markings, the flange in the middle of the second image is somewhat better: lol
The spacing between the water lines on the sealing surface is way too large
It is sufficient to conduct acceptance checks in accordance with the material specifications specified in the design requirements; thickness cannot be determined by visual inspection – measurements are needed instead. Additionally, for stainless steel, different specifications require retesting of the material at various proportions.
The thicker, the better. You can see that the higher the standard pressure rating of the flange, the thicker it is and the more screw holes it has.
Acceptance is carried out in accordance with the standards you require or the supplier’s standards (for dimensions), as well as through spectral analysis for material inspection
I’ve learned it, thanks for sharing your experience.