1. For the joint surface with large cylinder deformation or serious air leakage, use the method of grinding and scraping the joint surface
If the deformation of the joint surface of the upper cylinder is within 0.05mm, use the joint surface of the upper cylinder as the reference surface, paint red red or embossed blue paper on the joint surface of the lower cylinder, and scrape the lower cylinder according to the traces. If the deformation of the joint surface of the upper vat is large, apply red lead to the upper vat, use a large flat ruler to make traces, and grind the upper vat flat. Or take the method of mechanical processing to level the joint surface of the upper cylinder, and then grind and scrape the joint surface of the lower cylinder based on the upper cylinder. There are generally two methods for grinding and scraping the joint surface of the cylinder:
⑴It is the bolt that is not tight on the joint surface. Use a jack to slightly push the upper cylinder to move back and forth, and grind and scrape according to the coloring of the red lead on the joint surface of the lower cylinder. This method is suitable for high-pressure cylinders with strong structural rigidity.
(2) It is the bolt on the tight joint surface. Check the tightness of the joint surface according to the feeler gauge, measure the value and the traces of extrusion, and repair and scrape the joint surface. This method can eliminate the influence of the vertical arc of the cylinder on the gap.
2. Use proper cylinder seal material
Because there is no unified national standard and industry standard for steam turbine cylinder sealant, the raw materials and formulas are also different, and the product quality is uneven; Guaranteed regular manufacturers to ensure the tightness of the cylinder after maintenance.
3. Local repair welding method
Since the joint surface of the cylinder is scoured or corroded by steam to form groove marks, choose an appropriate welding rod to fill the groove marks, use a flat plate or a flat ruler to grind out the marks, and scrape the weld bead and the joint surface in the same plane. When the deformation of the joint surface of the cylinder is large or the steam leakage is serious, repair one or two 10-20mm wide sealing strips to eliminate the gap on the joint surface of the lower cylinder, then use a ruler or buckle the upper cylinder to measure, and apply red red to grind and scrape , until the gap is eliminated. The process of this operation is also very simple. Preheat the cylinder to 150°C before welding, and then perform segmental desoldering or skip welding at room temperature. Use austenitic electrodes, such as A407 and A412, and cover them with asbestos cloth to keep warm and cool slowly after welding. After cooling to room temperature, perform grinding and scraping.
4. Coating or spraying of the joint surface of the cylinder
When there is a large area of air leakage on the joint surface of the cylinder, and the gap is about 0.50mm, in order to reduce the workload of grinding and scraping, the coating process can be used. Use the cylinder as the anode, and the coating tool as the cathode, and repeatedly brush the electrolytic solution on the joint surface of the cylinder. The thickness of the coating depends on the size of the gap between the cylinder joint surface, and the type of coating depends on the material of the cylinder and the repairing method. Depending on the process. Spraying is to use a special high-temperature flame spray gun to heat the metal powder to melt or reach a plastic state, and then spray it on the surface of the treated cylinder to form a layer of coating with the required properties. It is characterized by simple equipment, convenient operation and firm coating. After spraying, the cylinder temperature is only 70°C-80°C, which will not cause deformation of the cylinder, and can obtain heat-resistant, wear-resistant, and corrosion-resistant coatings. It should be noted that the cylinder surface must be polished, degreased and roughened before coating and spraying, and the coating should be scraped after coating and spraying to ensure the tightness of the bonding surface.
5. The method of padding the joint surface
If the local gap leakage of the joint surface is not very large, 80-100 mesh copper mesh can be used to reduce the hardness after heat treatment, then cut into an appropriate shape, spread on the air leakage of the joint surface, and then add cylinder sealant. If the gap between the joint surface is large and the leakage is serious, a groove with a width of 50 mm and a depth of 5 mm can be opened on the upper and lower joint surfaces, and an IGr18Ni9Ti tooth-shaped pad is inlaid in the middle. The thickness of the tooth-shaped pad is generally 0.05-0.08 mm larger than the depth of the groove. It can be adjusted with stainless steel shims of the same shape.
6. Methods of controlling bolt stress
If the deformation of the joint surface of the cylinder is small and uniform, replace with new bolts where there is a gap, or properly increase the pre-tightening force of the bolts. Tighten from the middle to both sides at the same time, that is, tighten the bolts from the place where the vertical arc is the largest or where the force and deformation are the largest. Theoretically speaking, the pretightening force of the control bolt can be calculated by the formula d/L≤A, but because the calculation data and measurement methods are still under study, it has not been promoted, and it is mostly within the maximum allowable stress of the bolt according to experience. depends.
7. The polymer material method adopted in the new era
With the further development of technology, polymer composite materials have gradually been successfully applied in cylinder maintenance. Compared with traditional methods, polymer composite materials have excellent temperature resistance, good pressure resistance, and better sealing performance, and have good plasticity, will not cure when heated, and the sealing film will not be damaged. damage, thus ensuring the sealing of the sealing surface of the machine parts; in addition to being easy to remove, the used sealing surface can be easily wiped off with absolute ethanol or acetone without adhering to the sealing surface; More and more cylinder enterprises of all ages.