What is the difference between octagonal gaskets and elliptical gaskets?

As long as the passage diameter and pressure rating are the same, the sealing groove will be identical. Elliptical gaskets provide linear sealing, while octagonal gaskets offer surface sealing; in theory, they can be used interchangeably. https://bbs.hcbbs.com/thread-2121495-1-1.html

As the name suggests, an octagonal gasket has eight surfaces. For a certain type of valve whose connection method is RTJ, its sealing groove is trapezoidal in shape; in such cases, an octagonal gasket is required when installing it on the pipeline. Under high temperature and pressure conditions, octagonal gaskets and elliptical belt gaskets can theoretically be used interchangeably, but from a design perspective, it is better not to do so. If an octagonal ring is needed, then using an octagonal ring is the best option, as this can significantly reduce the risk of pipeline leaks.

We have a project that involves high temperatures and pressures. The initial design called for octagonal gaskets, but there were many minor leaks; no matter what measures were taken, these leaks persisted. Eventually, we had to replace the gaskets in the areas where leaks occurred with elliptical gaskets, and that stopped the leaks. However, the sealing surfaces of the flanges were still designed to use octagonal gaskets

This might be because the surface wasn’t properly processed. Ring connections require relatively high standards in terms of processing techniques.

I happened to have also studied this topic*.

One of my high-pressure pipelines used elliptical gaskets, and there was a leak; switching to octagonal gaskets resolved the issue. It’s exactly the opposite of you. .

So, have you analyzed what the reasons are? What is the final conclusion?

The octagonal pad and the elliptical pad can theoretically be interchanged. Some people said that ellipses aren’t suitable, so octagons would be a better choice; others said that octagons aren’t suitable either, so ellipses would be a better option. In fact, whether the sealing meets the requirements depends mainly on two aspects: 1. The finish of the sealing surface – whether it’s an octagonal gasket or an elliptical gasket, standards specify certain requirements regarding the finish of the sealing surface; if it’s too rough, it is not conducive to effective sealing ； 2. Material hardness: The sealing standards specify a range for the hardness of metal gasket materials; if the hardness is too high, the gasket does not deform easily, resulting in poor sealing performance. So, it’s not that octagonal pads are better or elliptical pads are better; as long as the surface finish is well controlled during processing and the hardness of the material is properly managed, both types are good.