Problems with flange connections using different standards
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We have a piece of equipment; the pipeline flanges are of the standard specified by the Ministry of Chemicals, while the valves were purchased according to the standards set by the Ministry of Machinery. These are two different standards, but the pressure rating and nominal diameter are the same. Can they be connected together? Is there any specification or standard that addresses this issue? I’d appreciate advice from those with more experience
This is all **standard, right? I haven’t heard of standards for two departments.** The Ministry of Chemical Industry has been dissolved. You might be referring to standard parts and non-standard parts? If that’s not possible, purchase according to the drawings, indicating the hole spacing, inner and outer diameters and thickness, whether there are raised or recessed surfaces, whether it is a high-neck flange, and the pressure rating and material.
For our pipeline flanges, we use the HG/T20592 standard, while the manufacturers of flange connections for valves follow the JB/T74 standard. Now the owner has raised this issue during the inspection: the thickness of the flange connection differs from the outer diameter, but the diameter of the bolt holes and the hole spacing remain the same. I don’t know how to explain things clearly to the owner now
It’s indeed different; the Mechanical Department doesn’t require us to produce according to the B series. When making purchases, standards are essential, and the more detailed they are, the better. Be sure not to make any mistakes!
The standards are different, so in most cases connection is not possible. Even when a connection can be established, it’s only for certain specific dimensions; by coincidence, the differences are small enough to allow such a connection. Look at the posts I replied to before; they all recommend using the US standard.
When planning a project, the client should establish unified standards for components such as valves and flanges that are used in large quantities. When making purchases, it is essential to pay close attention to all the requirements specified by the client; flanges with different standards cannot be fitted together properly, and if the client checks carefully, he or she will definitely point this out. I think in this situation, it’s still better to purchase flanges according to valve standards, after all, valves are more expensive. :lol
Check whether the flange bolt hole pitches of the two adopted standards are the same
Check the data against two standards. Generally, they can be paired, with an outer diameter difference of up to 5mm
Conversion flanges are used in the oil industry; the two ends can be flanges with different pressures and different diameters.
There are still some differences between the flanges used in the machinery industry and those used in the chemical industry. Piping angle: The flanged piping for JB’s mechanical department consists only of B-series metric pipes. The flanges of the HG Chemicals Department come in two series: A and B. Flange size angles: For some sizes specified in JB, the outer diameter differs by 5 mm from that specified in HG. For example, for a PN1.6 Mpa DN100 flange, the outer diameter according to HG is 220 mm, while according to JB it is 220/215 – meaning that both 220 mm and 215 mm satisfy the requirements.
If the bolt diameters and bolt specifications of the two flanges are the same, as well as the dimensions of their sealing surfaces, then they can be used. If the outer circles of the flanges are not aligned, it may not look good, but it does not affect functionality. Otherwise, flanges of the same standard must be used.