Regarding the flange sealing surface steps
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We are aware of the common RF faces: the national standard generally specifies a 45° angle, while the American standard uses a 90° right angle. However, in actual manufacturing, when a 45° angle is used – especially for flanges of grade PN40 and above – drilling often goes all the way to the flange’s sealing surface. I would like to ask whether, according to the national standard GB/T9113 and the German standard EN1092-1, it is allowed to use a 90° right angle when machining the steps on the flange’s sealing surface
How could it get stuck in the flange seal? They all need to be larger than the diameter of the boss, right?
For PN40 and DN300 and above, you can simulate how drilling is carried out and then you’ll understand. . .
It’s impossible to drill all the way into the hole; there will always be some excess
I don’t see any standard specifying that it’s 45°. . . So, this is not a critical dimension.
According to HG/T20592, for PN40 DN300 RF: the distance from the edge of the bolt hole to the sealing surface is 3.5 mm, and the height of the sealing surface is 2 mm. . For PN40 DN350 RF, the distance from the edge of the bolt hole to the sealing surface is 4.5 mm, and the height of the sealing surface is 2 mm. . For PN40 DN400 RF, the distance from the edge of the bolt hole to the sealing surface is 5.5 mm, and the height of the sealing surface is 2 mm. . If the pressure is even higher and other sealing surfaces are used, you need to set it at 45°, which would then result in it touching the circle of the bolt hole. . So, I’m not sure – where exactly is it mandated that the 45° chamfer on this sealing surface be present?
This post was last edited by COLORZERO on 2017-5-22 09:22. Do you want to see the standard? I’ll give it to you. . I can’t understand German, but it means the same thing
This is acceptable, as it allows manufacturers to produce components from different angles. In actual production, I’ve encountered many cases where the RJ surface of standard flanges came into contact with the sealing surface after drilling; in other cases, there was no such contact. However, when removing burrs from the bolt holes, contact still occurred. The standards still need further refinement
The European system flanges specified in GB/T 911 are identical to those in EN1092; the height of the sealing surface varies as the nominal diameter increases. Regarding the transition of this sealing surface step, the standard specifies that the manufacturer should control it to be at 45°; other angles or arcs can also be used. 1092 states that the transition from the edge of the raised face to the flange shall be: a) a radius, or b) a chamfer, as chosen by the flange manufacturer. Therefore, 45° is not mandatory
I just want to gently point out that it’s not appropriate to use GB/T recommended standards to discuss matters related to mandatory requirements
With 2 heights in the Ministry of Chemical Industry, it’s naturally impossible to collide. . . Take a look at GB/T9113 or EN1092-1