1. The cylinder is cast, and the cylinder must undergo aging treatment after leaving the factory, so that the internal stress generated by the cylinder during the casting process can be completely eliminated. If the aging time is short, the processed cylinder will be deformed in the future operation.
2. The force on the cylinder during operation is very complicated. In addition to the static load such as the pressure difference between the inside and outside of the cylinder and the weight of the parts installed in it, it also bears the reaction force on the static part when the steam flows out of the stator. And the force on the cylinder under the cold and hot conditions of various connecting pipes. Under the interaction of these forces, the cylinder is prone to plastic deformation and leakage.
3. The load of the cylinder increases or decreases too fast, especially when the temperature changes greatly during rapid start-up, shutdown and working conditions, the way of warming the cylinder is incorrect, and the insulation layer is opened too early when the shutdown is overhauled, etc., in the cylinder and on the flange Generate a lot of thermal stress and thermal deformation.
4. The cylinder produces stress during machining or after repair welding, but the cylinder is not tempered to eliminate it, resulting in a large residual stress in the cylinder and permanent deformation during operation.
5. In the process of installation or maintenance, due to the maintenance process and maintenance technology, the expansion gap of the inner cylinder, cylinder partition, partition sleeve and air seal sleeve is not suitable, or the expansion gap of the lug pressure plate is not suitable, After operation, a huge expansion force is generated to deform the cylinder.
6. The quality of the cylinder sealant used is not good, there are too many impurities or the model is wrong; if there are hard impurity particles in the cylinder sealant, it will make it difficult for the sealing surface to be tightly combined.
7. The tightening force of the cylinder bolts is insufficient or the material of the bolts is unqualified. The tightness of the cylinder joint surface is mainly realized by the tightening force of the bolts. The thermal stress and high temperature generated when the unit starts and stops or when the load is increased or decreased will cause the stress relaxation of the bolts. If the stress is insufficient, the pre-tightening force of the bolts will gradually decrease. If the bolt material of the cylinder is not good, the bolt will be elongated under the action of thermal stress and cylinder expansion force during long-term operation, and will be plastically deformed or broken, and the tightening force will be insufficient, causing the cylinder to leak.
8. The sequence of tightening the cylinder bolts is incorrect. Generally, the cylinder bolts are tightened from the middle to both sides at the same time, that is, from the place where the vertical arc is the largest or the place where the force and deformation are the largest, so that the gap at the most deformed place will be tightened to the free front and rear of the cylinder. The end shifts, and finally the gap gradually disappears. If it is tightened from both sides to the middle, the gap will be concentrated in the middle, and the joint surface of the cylinder will form a bow-shaped gap, causing steam leakage.