Expansion joint installation issues

Some expansion joints require pre-stretching (at high temperatures) or pre-compression (at low temperatures) during installation.

It’s definitely different; consulting the manufacturer will give the most accurate answer

Pre-stretch and pre-compress according to the design temperature and expansion/contraction requirements

@Shuguang bellows, please help solve this!

This post was last edited by Dawn Bellows on 2015-8-12 at 17:02. The greater the temperature difference, the greater the amount of expansion (displacement)； Before manufacturing, the manufacturer must consult with the user to understand and clarify the maximum temperature, minimum temperature, and installation temperature, as well as the areas where significant changes may occur during pipeline installation. Pre-positioning may be necessary when installing expansion joints, and it is also important to determine whether insulation layers are required in order to enable proper design of the expansion joint components. In general, expansion joints that are subject to internal pressure at high temperatures need to be pre-deformed before installation (since the pipelines expand significantly under high temperatures, causing the expansion joints to be compressed) in order to reduce their elastic force ； Low temperatures mainly cause cold shrinkage; pre-stretching is required during installation ； High temperature is mainly due to thermal expansion; pre-compression is required during installation ； The bellows materials used in high-temperature and low-temperature conditions are different, as the allowable stress of materials varies at different temperatures; thus, rigid connections are replaced with flexible connections ； In applications with high operating temperatures, in order to reduce the temperature of the bellows and maintain its mechanical properties, thermal-insulating ceramic fibers can be filled between the bellows and the inner cylinder, or a purge pipe can be installed to use air flow to lower the actual temperature of the bellows.

Thank you so much; it was a highly professional answer – I’ve learned a lot

Today’s expansion joints are pre-stretched or pre-compressed, and they all have positioning bolts to hold them in place. Depending on the direction and magnitude of displacement, the limiting bolts on the expansion joint are loosened

Install it as specified in the technical documents; don’t overthink it.

Expansion joints should be used for high-temperature pipes, while flexible metal hoses should be used for low-temperature pipes.

I hadn’t noticed that before; I need to go to the site and investigate how the expansion joints were installed at that time