Why are loose-flange types not included in the ASME/ANSI B16.47 standard?
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This issue has been bothering me for a long time: why are there only three types of flanges specified in the large-diameter flange standard B16.47, namely BL, WN, and RJ? We need 60\" 300# loose-flange 304 steel flanges to be used in combination with flanged ends, and the material list indicates that ASME B16.47-B should be referenced. How should we determine the dimensions of these flanges?
Loose-fit connections are commonly used in environments with corrosive media, and the flanges and flanged splices are made of different materials to save costs. There are no large-diameter sizes specified in the standards. I believe the reasons for this are as follows: 1. The flanged joint and the flange itself are not firmly connected to each other, resulting in poor integrity and low rigidity; this makes it easy for uneven stress distribution to occur at larger diameters. 2. Based on the first point, the sealing is poor. 3. Due to the connection of different materials, galvanic corrosion is likely to occur when electrolytes such as water are present. Although this can be resolved by painting, the larger the diameter, the greater the surface area; if there is any corrosion, the remaining part will also be affected. 4. When the temperature of the medium is high, there is also the issue of compositional diffusion between different materials, which may cause changes in the structure and properties of those materials. For example, when a loose-flange made of carbon steel comes into contact with a stainless-steel flanged stub, high temperatures can cause carburization of the stainless steel. It is detrimental to the mechanical properties and corrosion resistance of the material.
The loop flange is not welded on; I think it can be used in applications with low pressure, as ASME B16.47 is a bit conservative
Yes, it’s secured with screws. The question is, how do you determine the size?