Is the thermal tightening of catalytic hydrogenation units carried out in a hydrogen environment or a nitrogen environment?

Then perform heat tightening at 250 under a hydrogen environment

1. Whether in hydrogenation units or other environments with high temperature and pressure, heat-tightening of flange bolts is generally practiced; indeed, some companies have systems or regulations that specify the requirements for such heat-tightening. One might ask: why is thermal fastening necessary, and what is the evidence supporting this approach? 2. From the installed state to the operating state, the stresses on flanges, bolts, and gaskets change as the pressure and temperature of the medium vary. These stresses are also affected by the uniformity of the bolt loads and their initial values, as well as by the compatibility of the materials used for the flange bolts. It is a complex system with numerous variables that influence one another. 3. As another example illustrating a different perspective, a simplified model with certain variables already determined is used for ease of explanation: for instance, the coefficients of thermal expansion of the flange bolts are assumed to be the same, the loading on the bolts is uniform, deformation due to the thickness of the flange under stress is ignored, and the creep effect of the bolts is also neglected. Only the metal temperature of the flange bolts and the increase in pressure of the medium are taken as variables to examine the ability of the gasket to withstand internal pressure, with two simplified curves used for comparison. 3.1. When there is a certain temperature difference between the flange and the bolts, when the medium temperature reaches 350°C, the actual load on the bolts is less than the required load, resulting in leakage from the gasket. 3.2. Under the same temperature difference between the flange and the bolts, by increasing the pre-tightening load of the bolts, the actual load on them becomes less than the required load only when the medium temperature reaches 490°C. 4. It can be seen from this simplified model that, provided the material properties of the bolts permit it, increasing the pre-tightening load of the bolts can achieve the same effect as thermal tightening. The zero-leakage installation method currently being adopted in refineries often relies on increasing the pre-tightening load, thereby achieving a uniform bolt load during cold-installation, and thus avoiding the risky practice of hot tightening under pressure when the system is heated. 5. The above description does not negate the need for hot tightening; each method has its advantages and disadvantages, and different users have varying opinions on this matter. Our criterion for judgment is to choose the lesser of two evils.

Thank you; this reply is perfect

Thank you; this reply is perfect

Thank you; this reply is perfect

Two heat sets at 150 degrees and 250 degrees.