Why is heat tightening required for the connection of carbon steel graphite gaskets?

It mainly depends on the operating temperature; if it exceeds 200°, thermal tightening is required, while if the temperature is below 200°, tightening it properly during installation is sufficient.

I’ve never heard that heating is necessary for tightening; if there are such regulations, I’d like to know about them as well

I don’t know; I’ve never heard of it. Does anyone who knows know how to explain it?

1. Not all gasketing materials need to be heat-shrunk. Generally, heat tightening is required when the operating temperature is above 200°C. Some factories are quite strict with themselves; to prevent leaks, they tighten the connections even at 150°C. Generally, heat tightening is performed once at temperatures below 350°C; for temperatures above 350°C, a second heat tightening is required after the working temperature is reached. Thermal tightening is particularly important when the unit is started and stopped frequently or immediately after an emergency stop. Thermal tightening is necessary not only for carbon steel graphite gaskets, but also for stainless steel graphite gaskets, octagonal gaskets, and similar ones when the temperature is above 200°C. 2. Reason for thermal tightening: Bolts deform at high temperatures, and due to the tensile forces applied, they experience microscopic growth. And the increase in the length of the gasket is very small. Therefore, the flange connection becomes loose at this point, and the bolt preload decreases. To ensure sufficient bolt pre-tension and prevent leakage of the flange in the event of fluctuations in operating parameters, thermal tightening is required. What I’ve said might not be comprehensive, but I hope it can help you!