Dimensional requirements for RF flange metal winding gasket selection

Aren’t there standards? Do you want to design something non-standard?

HG/T20592 and NB/T47025 standards have specific dimensions. For non-standard flanges, you can refer to the standard dimensions.

Agree with the point above, look at the standards first

If it is a standard part, it is better to choose it according to the standard. If it is a non-standard part, it is better if the outer ring does not affect the bolt assembly.

I’m not a designer. We have a 30” ASME 900# RF flange. The outer diameter of the metal wound pad positioning ring is very close to the inner diameter of the flange bolt hole. The overall diameter difference is only 0.2mm. I just want to know if this size is reasonable.

These two sizes are very close, and the calculated diameter difference is only 0.2mm.

The ASME flange standard also has size regulations, but the sizes specified in the ASME standard are indeed very different.

You are right that the gap is indeed very small, but the gap does not need to be large, or if it is large, it may affect the sealing performance of the gasket. In theory, it does not affect the bolt assembly. The smaller the gap, the better the gasket centering can be ensured. And the 0.2mm you mentioned is the theoretical gap. In fact, the bolt holes are slightly larger than the bolts, so the assembly must be no problem. Whether from theoretical or practical considerations, this 0.2mm is reasonable.

I'll check if there is a specific standard number.

We checked this problem because the sealing gasket was damaged and the flange leaked. According to theory, there is definitely no problem. As long as the inner diameter of the positioning ring is smaller than the actual bolt hole, the sealing can be achieved without affecting the bolt passing through the bolt hole. However, there are four pipes around our flange. The pipes are equipped with expansion joint sheaths. The space itself is extremely narrow, which makes installation very difficult. In addition, the size is ten If it is very close, the gasket needs to be completely aligned with the flange. Because it is all manually installed, there will inevitably be deviation in the gasket alignment during the installation process. According to this design, as long as a slight unilateral movement of 0.1mm will enter the bolt hole, then there will be a bump on the gasket positioning ring during the bolt perforation process, which will directly affect the positioning and tightening of the outer ring of the gasket, eventually causing failure. So I wanted to consult with experts to see if this design selection is reasonable.