Causes of Air Leakage in Steam Turbine Cylinders

1. The cylinder is made of casting. After leaving the factory, the cylinder must undergo aging treatment, that is, it must be stored for some time to eliminate the internal stress ## generated by the cylinder during the casting process. If the aging time is short, the processed cylinder will be deformed in the future operation, which is why some cylinders will leak steam in the future operation after the ## 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 between the inside and outside of the cylinder and the weight of the parts installed in the cylinder, it also bears the reaction force of 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, plastic deformation of the cylinder causes leakage.

3. The load of the cylinder increases or decreases too fast, especially when the temperature changes greatly during rapid startup, shutdown and working conditions, the method of heating the cylinder is incorrect, the insulation layer is opened too early during the shutdown and maintenance, etc., in the cylinder and on the flange Produce great thermal stress and thermal deformation.

4. The cylinder produced stress during the machining process or after repair welding, but the cylinder was not tempered to eliminate it, resulting in large residual stress in the cylinder and ## 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 diaphragm, diaphragm sleeve and steam envelope sleeve is inappropriate, or the expansion gap of the lug pressure plate is inappropriate. After running, a huge expansion force is generated to deform the cylinder.

6. The cylinder sealant used is of poor quality, excessive impurities or the wrong model; if there are hard particles of impurity in the cylinder sealant, it will be difficult for the sealing surface to be tightly combined. VIF900 high temperature cylinder sealant is ##turbine cylinder sealing material, high, medium and low pressure cylinders can be used universally, avoiding cylinder leakage caused by improper model selection.

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 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 pre-tightening force of the bolts will gradually decrease. If the material of the cylinder bolt is not good, the bolt will be stretched under the action of thermal stress and cylinder expansion force during long-term operation, and plastic deformation or fracture will occur, and the tightening force will be insufficient, causing the cylinder to leak.

8. The tightening sequence of cylinder bolts is incorrect. Generally, cylinder bolts are tightened from the middle to both sides at the same time when tightening, that is, tighten from the vertical arc ## or the place where the force is deformed ##, so that the gap at the deformation ## will be toward the cylinder. The free ends before and after transfer, 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.