Why must cold exchange equipment be heat-tightened during startup?

At the start of operation of the unit, the main components and accessories of the heat exchanger equipment are connected by flanges and bolts, with gaskets used for sealing. Due to the difference in materials between them, during the heating process, especially in the area with hot oil (above 200°C), uneven expansion of various parts leads to flange relaxation and a decrease in the pressure on the sealing surfaces. At high temperatures, the elastic modulus of the materials decreases, causing deformation and a reduction in mechanical strength; this results in excessively high local stresses in the flange, leading to plastic deformation and the loss of elasticity. At this point, the pressure-seepage material has a significant impact; it may cause the gasket to move along the flange surface, resulting in leaks. The purpose of thermal tightening is to eliminate any slack in the flange, thereby ensuring that there is sufficient pressure on the sealing surfaces and thus maintaining the effectiveness of the static seal.

Maintaining a constant temperature of 250 degrees is very important for heat setting.