Flange manufacturers engage in cheating and cut corners in their work
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The valve manufacturers resorted to trickery by choosing flanges that were small and thin. The flange standards chosen by the pipe fitting manufacturers were acceptable, but they deliberately made the flanges 5 mm thinner. When the valves and flanges from these two manufacturers were brought to our construction site and connected together, their sizes and thicknesses did not match, which gave an awkward appearance. Sadly, this kind of behavior seems to occur in many factories and is widespread. The two matching flanges did not appear to be compatible with each other – can’t work be done more carefully?
Will the inspection pass like this? Is it 5 mm thicker than the standard? They dare to do this now.
It’s all because of the price, I guess; there are many such phenomena in the market. Winning the bid at a low price forces one to use less material during production.
Some companies still inspect the flanges upon receipt, but here we don’t inspect flanges, pipes, or fittings at all before putting them in storage. Besides, even if inspection were carried out, who would measure the thickness and outer diameter of the flanges? If measurement is necessary, one must first check the standards to see what the specified values are. But no one bothers to check the standards; they just use calipers for measurement
It seems we have quite strict acceptance standards. If there are problems with such flanges after they are used, isn’t both Party A and Party B responsible? Does the owner not care either?
Original poster: This is probably due to different standards being used in manufacturing. Generally, qualified manufacturers would not dare to blatantly reduce the size of flanges.
Of course, it’s not certain if products from unqualified manufacturers are purchased. I have also seen flanges made by directly casting crude flange blanks from domestically produced steel, and then machining them. :L
The pursuit of low costs is what leads to the existence of such flanges, which are what are known as non-standard flanges. This term was coined by the industry itself; such flanges are of extremely poor quality. There are also semi-standard flanges, which are only about 3 mm smaller than standard flanges in terms of both thickness and outer diameter. These types of products are manufactured by small workshops. To be honest, the reason such products exist is their low cost – they can be used in situations where there isn’t much pressure involved. But in applications that require higher pressure resistance, no one would dare use them, as it could lead to serious problems
If you take a closer look, 5mm should still be quite obvious