The cylinder is made of casting, and the cylinder must undergo aging treatment after leaving the factory, so that the internal stress generated by the cylinder during the casting process is completely eliminated. If the aging time is short, the machined cylinder will be deformed in the subsequent operation.
In addition to the static load such as the pressure difference of the gas inside and outside the cylinder and the weight of the various parts installed in the cylinder, it also bears the reaction force on the static part when the steam flows out of the stator, and the various Under the interaction of these forces, the cylinder is prone to plastic deformation and leakage.
The load of the cylinder increases or decreases too quickly, especially when the temperature changes rapidly during rapid start-up, shutdown and working condition changes, the method of warming up the cylinder is incorrect, and the insulation layer is opened too early during shutdown and maintenance, etc. Large thermal stress and thermal deformation.
Stress is generated in the cylinder during machining or after repair welding, but the cylinder is not tempered to eliminate it, resulting in large residual stress in the cylinder and permanent deformation during operation.
In the process of installation or maintenance, due to the maintenance process and maintenance technology, the expansion gap of the inner cylinder, the cylinder diaphragm, the diaphragm sleeve and the steam seal sleeve is not suitable, or the expansion gap of the hanging lug pressure plate is not suitable. A huge expansion force is generated to deform the cylinder.
The quality of the cylinder sealant used is not good, there are too many impurities or the wrong type; if there are hard foreign particles in the cylinder sealant, it will be difficult for the sealing surface to be tightly combined.
The tightening force of the cylinder bolts is insufficient or the material of the bolts is not qualified. The tightness of the cylinder joint surface is mainly achieved by the tightening force of the bolts. The thermal stress and high temperature generated when the unit starts and stops or increases or decreases the load will cause the stress relaxation of the bolts. If the stress is insufficient, the preload 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, plastic deformation or fracture will occur, the tightening force will be insufficient, and the cylinder will leak.
The cylinder bolts are tightened in the incorrect order. 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 place with the largest deformation will be adjusted to the freedom of the front and rear of the cylinder. End transfer, and finally the gap gradually disappears. If it is tight 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.
