Analysis Of The Cause Of Cylinder Failure

1. The cylinder is casting, and the cylinder must undergo aging treatment after leaving the factory, that is, it must be stored for some time to completely eliminate the internal stress generated by the cylinder in the process of casting. If the aging time is short, the processed cylinder will be deformed in later runs, which is why some cylinders will leak steam in later runs after the first leakage treatment. Because the cylinder is still constantly deforming.

2. The force of the cylinder during operation is very complicated, in addition to the static load such as the pressure difference of the gas inside and outside the cylinder and the weight of the parts installed in it, it is also subject to the reaction force of the static part when the steam flows out of the static blade, and the force on the cylinder under the cold and hot state of various connecting pipelines, under the interaction of these forces, the plastic deformation of the cylinder causes leakage.

3. The load of the cylinder increases and decreases too quickly, especially the rapid start, shutdown and temperature change during the change of working conditions, the way of warming the cylinder is incorrect, and the insulation layer is opened too early during shutdown and maintenance, etc., which produces great thermal stress and thermal deformation in the cylinder and on the flange.

4. The cylinder is stressed in the process of 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 in 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 separator, separator sleeve and steam seal sleeve is not suitable, or the expansion gap of the hanging ear pressure plate is not suitable, and the huge expansion force is generated after operation 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 to tightly bond the sealing surface. VIF900 high temperature cylinder sealant is the latest turbine cylinder sealing material, high, medium and low pressure cylinders can be universal, avoiding cylinder leakage caused by improper model selection.

7. The tightness of the cylinder bolt is insufficient or the material of the bolt is unqualified. The tightness of the cylinder joint surface is mainly achieved by the tightening force of the bolt. The thermal stress and high temperature generated when the unit starts and stops or increases or decreases the load will cause the stress of the bolt to relax, and if the stress is insufficient, the preload of the bolt will gradually decrease. If the bolt material of the cylinder is not good, the bolt is elongated under the action of thermal stress and cylinder expansion force during long-term operation, and plastic deformation or fracture occurs, and the tightness will be insufficient, so that the cylinder leaks.

8. The order of cylinder bolt tightening is incorrect. The general cylinder bolt is tightened from the middle to both sides at the same time when tightening, that is, from the largest vertical arc or the place with the largest force deformation, so that the gap at the largest deformation will be transferred to the free end before and after the cylinder, 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 cylinder joint surface will form a bow-shaped gap, causing steam leakage.