The thermal efficiency (especially the thermal efficiency of each cylinder) of the steam turbine unit in a large thermal power plant plays a decisive role in the safe production, economic operation and safe and civilized production of the unit, which is directly related to the economic benefits of the power plant and the safe operation of the unit. In this regard, power plants attach great importance to the maintenance of units, and have high requirements for the quality control of turbine maintenance, especially in turbine maintenance, the adjustment of steam gap should be more cautious, and the adjustment of flow gap determines the maintenance quality and improves the operation efficiency.

Keywords: steam turbine; Deformation measurement technology; Wo Wo deformation

Due to structural reasons, manufacturing reasons and thermal stress reasons, the cylinder of the unit has great deformation after operation. When the unit is overhauled, the deformation should be measured and analyzed first, and the reason of seal friction should be judged according to the analysis results, so as to narrow and correct the gap during overhaul. The dimple deformation technology is developed on the basis of accumulating a lot of experience in the transformation of the whole machine. We have noticed that cylinder deformation and diaphragm deformation are common in domestic units, which leads to the difference in the center of diaphragm pit between full cylinder and half cylinder, which not only affects the efficiency of gland clearance adjustment during unit maintenance, but also affects the concentricity of diaphragm static cascade and rotor moving cascade during operation, which affects the steam flow and reduces the thermal efficiency of the unit. In view of this situation, we have developed a measuring instrument for the deformation of clapboard pits, which has been successfully applied to hundreds of power plants and achieved remarkable results. Measuring the change of the pit relative to the whole cylinder in the state of half cylinder is the most critical link for us to really adjust the sealing gap. Only by truly mastering the deformation can the sealing gap be optimized and adjusted. Measuring the disintegration pits and ovality of the high-pressure steam inlet balance ring sleeve, then measuring the ovality of the seal after installation, and combining with the clearance standard of the last overhaul, determining the maximum elliptical trajectory of the rotor after operation is the basis for us to judge the installation clearance and optimize the seal clearance when the maximum deflection is achieved.

Deformation measurement of 1 sag

This work is generally carried out after measuring the joint clearance with an empty cylinder. If there is a large opening on the joint surface that needs to be repaired, the deformation of the pit needs to be measured after repair. In the overhaul unit, after the centers of all solid cylinders are qualified, the center of the static part should be statically calibrated. Static centering includes positioning ring, diaphragm sleeve, diaphragm, shaft sleeve and other components. In general, the dynamic and static center of the lower semi-solid cylinder shall prevail. In fact, the deformation of the high-pressure and low-pressure outer cylinders of the units that have been running is very large. In general, there is a large gap between the center of the dynamic and static depression of the lower semi-solid cylinder and the center of the dynamic and static depression under the fully solid cylinder. Regardless of the dynamic and static concentricity under the all-solid cylinder, the overhauled unit often has dynamic and static rubbing noise when starting, and the full-speed start is not smooth. When the friction sound is small, the unit also reaches full speed, with load efficiency (heat consumption, steam consumption, coal consumption) In order to improve efficiency, it is considered that:

1) The false shaft shall be subject to the qualified oil retaining socket in the rotor center. Find and record the dynamic and static centers of the middle and lower real cylinders, including retaining ring, diaphragm sleeve, diaphragm and shaft sleeve. Then begin to measure and record the dynamic and static centers of the lower half cylinder (retaining ring, diaphragm sleeve, diaphragm, shaft sleeve, etc.). ). There is a gap between the centers of dynamic and static depressions under the full-scale cylinder and those under the half-scale cylinder. In the process of maintenance, the actual dynamic and static hollow under the full-size cylinder should be corrected to the dynamic and static hollow of the half-full cylinder. Then adjust the gland clearance on the full-size cylinder. After the gland clearance is adjusted to be qualified, it will start smoothly, there will be no static and dynamic friction, and the load efficiency will be greatly improved (turbine installation and maintenance), which is actually the process of adjusting the static and dynamic center under full cylinder. Especially in units that have already undergone surgery. The metal material of the equipment has solidified after a long time of stress failure.

2) The high and low pressure outer cylinders are not adjustable, and the dynamic and static center under the whole cylinder should be considered for the overhaul unit.

2 Probe arrangement of dent deformation measuring instrument

Before measurement, the measuring points of each depression should be marked (measuring 3 points, namely, left A, right B and lower C), so as to measure at the same position every time and improve the measurement accuracy. Tighten the diaphragm and the inner cylinder of the semi-clamping ring, and re-measure the plane clearance of the cylinder in the natural state. If it is the first overhaul, it is recommended to measure the center of each part again before tightening the bolts. (Let's measure the next three points) As we all know, in the semi-cylindrical state, the stiffness of a cylinder is lower than that of a full cylinder. Especially the rigidity of the cylinder closing machine is poor. After hanging the upper snap ring and the inner cylinder, the cylinder will deform downward under the action of the upper weight. This number should be a measured value, and the measured result can be used as a reference for future maintenance at any time. Tighten 1/3 bolts according to the plane clearance distribution. After the bolts are tightened, the maximum clearance of flange plane should be less than 0.05 mm ... If the clearance exceeds the standard, tighten all bolts; If the clearance still exceeds the standard after all bolts are tightened, tighten the bolts until the maximum clearance on the flange plane should be less than 0.05 mm. (Except a few edges) After tightening the bolts, measure the hollow center of the retaining ring and the inner cylinder. When measuring the inner cylinder, we require the measurement technology and measurement requirements to be completely consistent with the measurement of the outer cylinder. When we fasten the inner and outer cylinders, we will measure the hollow center through the upper measuring point, the lower measuring point, the left measuring point and the right measuring point. In this measurement process, it should be analyzed according to the center change of the measurement of the inner cylinder and the outer cylinder. Usually, the center change of the inner cylinder and the outer cylinder is caused by the problems of the open flange and bolt fasteners. Therefore, when we deal with it, we should check the rigidity and verticality of bolt fasteners, because once there is a problem with the strength and verticality of bolt fasteners, it will affect the fulcrum elevation of inner and outer cylinders. Through the measurement of the cylinder block, it can be analyzed from the measurement results that the real center between the inner and outer rings of the cylinder and the partition plate is the real center position of the pit. Like the previous measurement operation, the outer cylinder should be buckled when measuring, but the bolt and flange cannot be connected in this process, so the change of the center of the ring and the center of the inner cylinder can be measured by the gravity of the outer cylinder itself. After opening the cylinder, we need to recheck all kinds of center change data, and then compare the recheck results with the last measured data. If the second measurement data does not change much, we think that the deformation of the cylinder is relatively stable. If the second measurement data changes greatly, it means that the center of the cylinder changes greatly. We need to analyze this change, find out the reason of the center change, and ensure the reliability of the measurement results. By comparing the measurement results, the change of the center of each gland sleeve after the cylinder bolt is tightened is calculated. When the cylinder is open, adjust the hollow center of the retaining ring and the baffle according to the actual deviation and change, so that it is concentric with the rotor after the cylinder is closed. In other words, the dimple in the full cylinder state is equal to the left and the upper is equal to the lower.

Considering the actual situation on site, the inner diameter of some channels is small. In most cases, people can't enter after the upper holding ring is locked with the inner cylinder, and only three points can be measured after the outer cylinder is closed. Therefore, it is necessary to measure the ovality of each retaining ring and inner cylinder in the natural state and after tightening the flange bolts, and consider this part when calculating the change of the concave center of each gland after tightening the cylinder bolts. Through accurate deformation measurement, we can better grasp the actual changes of half-cylinder and full-scale cylinder, more accurately grasp the value of sealing adjustment gap, ensure that the adjusted sealing gap is more real and reliable, and realize the optimal adjustment of sealing gap. In the process of steam turbine application, the application efficiency has a great influence on the whole unit, which is directly related to the normal operation and economic benefits of the unit. It is for this reason that during the normal operation of the unit, it is necessary to conduct a comprehensive inspection of the steam turbine, especially the deformation of the cylinder. In the process of cylinder deformation detection, the cylinder clearance should be mainly checked. Only in this way can the use effect and performance index of the cylinder be effectively checked. In order to effectively reduce the huge workload brought by the cylinder inspection process, the radial clearance of the cylinder should be adjusted as much as possible during normal inspection to ensure that the cylinder clearance meets the application standards.

3 Conclusion

Through the application of this technology, it provides basic data for the adjustment of steam seal gap and the scraping technology of steam barrier with cylinder during maintenance, thus achieving the ultimate goal of optimizing steam turbine flow gap, providing a strong technical guarantee for improving steam turbine cylinder efficiency and thermal efficiency of the unit, thus reducing the coal consumption value of the unit and providing a feasible solution for reliably reducing the power generation cost of the power plant.

refer to

[1] National Energy Administration. DL/T869—2065438+02dl/T753—20065438+0, Technical Specification for Welding of Thermal Power Plants [S]. Beijing: China Electric Power Press, 20 12.

[2] State Economic and Trade Commission. DL/T753—200 1, Technical Conditions for Repair Welding of Steel Castings of Steam Turbine [S]. Beijing: China Electric Power Press, 200 1.

National Energy Administration. DL/T8 19—20 10, Technical Specification for Welding Heat Treatment of Thermal Power Plants [S]. Beijing: China Electric Power Press, 20 10.

;