Effect of Temperature on Bolted Flange Assemblies

Bolted flange assemblies are helpful to connect widely with different elements of the pipelines and pressure vessels. They carry process media at temperatures that vary from cryogenic to more than 1000°C. Thermal transitions and high temperatures play a vital role in the tightness of bolted flange assemblies. We can quickly encounter the unfulfilled tightness that may occur due to thermal effects. It becomes easier if the assembled components (gaskets, bolts, and flanges) are in limits, and do not undergo mechanical failure.

Characterize the temperature effects

The temperature during the process is bound to rise. It demands the improvement in the chemical efficiency that drives the process. It is why; components like gaskets must be able to withstand the increase very quickly.

Characterizing the temperature effects on the flange bolting assemblies will always remain a crucial issue. Not only for the end-users but also for the designers as it involves complex physical laws. The reason is that the temperature directly impacts all the different elements of the bolted assemblies. The impact can split into two different perspectives:

1. Modification of flanges / bolts elastic interactions.

2. Modification of the gasket’s properties

Another temperature effect is the oxidization of the gaskets based on graphite. Gaskets that successfully prove the effectiveness of a flange fitting for a given period; need careful examination for oxidation. It must happen before their use.

Address the effects

The effects on the flanges and bolts assembly are not addressed by the traditional ‘Taylor Forge’ calculations, apart from the impact on the material stress limit. EN1591 has made a significant improvement with the introduction in the assessment of differential axial thermal expansions between the flanges and bolts.

The differential axial thermal expansion is said negligible and unaddressed if:

1. The difference in the thermal expansion coefficient of the different components of the bolt joint doesn’t exceed 10% if the temperature of the vessel design is above 120°C.

 2. The temperature difference between the bolt and flange is within 50°C.

Conclusion

The temperature plays a crucial influence on the tightness of flange connection and assemblies and must be considered carefully by the designers and end-users. If you have any questions about the effect of temperature on bolted flange assemblies, let us know in the comment section.