Bolt torque calculation in flanges with spiral wound gaskets

[antopax]

Hi, I am calculating the correct bolt torque for some flanges with stainless steel spiral wound gaskets, graphite filled, but I cannot find the modulus of elasticity of the gasket itself. I found values of m and Y, but Y is the seating stress, which is the initial value before to apply the correct torque value to have the correct sealing. I'm looking for the "spring costant" for these gaskets.
Suppliers don't give so much infos.
Any help is really appreciated.
Ciao
Antonio

 

[TGS4]

You need to apply sufficient bolt load in order to seat the gasket and maintain sufficient gasket contact pressure to withstand the internal pressure and any imposed external loads such as piping-induced bending moments and axial forces as well as those loads due to flange misalignment.

Also, the elastic modulus is not a constant value like you would find for typical metals. It is different in loading compared to unloading - often very different. That's why the gasket manufacturers won't give you a "number", it's because there is no one number.

What about following the "guidance" found in ASME PCC-1 and use their torque charts?

 

[JJPellin]

Spiral wound gaskets that I am familiar with have a metal ring on the OD (and sometimes the ID). The flange face bears down on the metal ring which assures that the spiral wound portion is compressed properly. The spring constant of the spiral wound portion of the gasket is not key to determining the torque. The clamping force of the studs needs to keep the flange faces in contact with the metal ring under all pressure or temperature conditions. If the flange faces always stay in contact with the metal ring, the comprssion of the spiral wraps never changes.

Johnny Pellin

 

[antopax]

Thank you for the information given. It is the first time I am facing this subject, and I will analyse it deeply in the next two weeks of my holidays!!
See you on next thread.
Antonio

 

[MJCronin]

antopax....

It is my understanding that for piping systems, spiral wound gaskets are simply torqued to nominal values based on the bolt size and material.

Flexitallic and other manufacturers offer bolt torque tables in thier sales literature.

Why are you calculating bolt torques ?

-MJC