Regarding the selection of mating flanges
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I have a question for everyone: There is a furnace used in catalysis; it was originally equipped with an access hatch made of 16Mn material, with an outer diameter of 732 mm and a thickness of 16 mm. There is also an insulating lining inside the flange. Now I want to remove the access hatch cover and install a flange in its place. The thermal engineering team has specified a temperature of around 650 degrees and a pressure of 0.3 MPa. I would like to ask everyone how I should select the appropriate flange for this purpose 1. I originally wanted to cut off the existing flange and install a new pair of DN700 flanges – would 304 work? Another issue is that the original flange used JB4700 standards, with an inner diameter of 700; the 650-degree temperature standard no longer applies in this case. The standard outer diameter for use in the chemical industry is 720 – can it be welded directly using PL? 2. I asked the workshop yesterday; they said that since the original flange cannot be moved, it’s necessary to use one that can withstand high temperatures. One of these flanges is made of low-alloy steel, and the other from high-alloy steel. Won’t the sealing performance of these two types of flanges be poor? It also deforms easily?
In my opinion, if the mating flanges are not lined, and a high-temperature-resistant superalloy stainless steel flange is connected to a low-alloy steel flange, the operating temperature of the 16Mn flange, due to heat transfer, should be relatively high. The operating temperature for low-alloy steel is generally required to be below 425°C; above this temperature, the cementite in the steel undergoes graphitization, which ultimately leads to a reduction in the strength and ductility of 16Mn flanges, resulting in deformation and other issues. . . .
If a complete redesign is needed, can 304 material be used?
4# Grace 304 is certainly an option, but it’s quite expensive. I recommend using 12Cr1MoV, as its temperature properties are just right
I checked, and the maximum heat resistance temperature of 12Cr1MoV is less than 600 degrees