Aren’t there many valves or flow meters that are DN32?

　　It’s not like that. There are still many control valves of DN32. 　　However, WuZhong Instrument Factory introduced the control valve manufacturing technologies of Japanese Yamaki and German ARCA on two occasions, in 1980 and 2002. Its ARCA series products are available in sizes of 2/3 inch, 1 inch, 1.5 inch, and 2 inch; there is no size of 1-1/4 inch, and therefore no corresponding size of 32 mm. 　

DN32 is not commonly used for regular piping, but this doesn’t apply to the outlet flanges of control valves and pumps; the value calculated is what it is. Even on-site, DN125 control valves can be seen.

General pipeline design principles: Try to avoid using sizes such as 1-1/4”, 2-1/2”, and 5”. This also applies to control valves; try to avoid them as well, otherwise the pipeline team will have to purchase pipes and fittings specifically for these sizes of control valves. Since the spool of the control valve can have a reduced diameter, this issue can be addressed in the following way: I can choose a control valve with a full-bore diameter of DN32 (if such a size is available), or I can opt for one with a valve body diameter of DN40 and a spool diameter of DN32; the flow capacity of both options is the same, so I will choose the latter. For special material pipelines with high prices, the diameter of the control valve should be determined in advance. DN32 valves are slightly cheaper than DN40 valves, but the materials used for the pipes and flanges also need to be taken into consideration; such \"rare sizes\" require special orders as well, and a lead time is necessary for their procurement. In the future, there will be a missing flange on site, and no stock is available to replace it. @jiaguoyun

Sizes such as 1-1/4”, 2-1/2”, and 5” are not available on many brands of flowmeters and control valves, as this range of pipe diameters overlaps with those of other commonly used diameters.