**1. Surface Scraping Method for Large Deformations or Steam Leaks in the Cylinder Joint**
If the bonding surface of the cylinder is deformed by more than 0.05mm, use the cylinder surface as a reference and apply red lead or blue paper on the adjacent cylinder. Then, scrape the next cylinder according to the marks left. If the upper part of the cylinder is significantly deformed, apply red lead on the upper cylinder and use a straightedge to remove the high spots and level the surface. Alternatively, machine the upper cylinder joint surface to make it flat, then use it as a reference to scrape the lower one.
There are two common methods for scraping the cylinder joint surface:
(1) For bolts that are not tightly fastened, use jacks to slightly move the upper and lower cylinders forward and backward, then scrape based on the red lead markings from the lower cylinder. This method works well for high-pressure, rigid cylinders.
(2) For bolts with tight joints, check the tightness using a feeler gauge and measure the pressure marks. This approach helps eliminate the influence of the cylinder's curvature on the clearance.
**2. Use of Appropriate Cylinder Seal Materials**
Since there is no unified national or industry standard for turbine sealants, materials and formulations vary widely, leading to inconsistent quality. When selecting sealants, choose those from reputable manufacturers known for reliable product quality to ensure proper sealing after maintenance.
**3. Local Welding Method**
When the cylinder joint surface is severely worn or has deep grooves, select an appropriate electrode and weld a small bead along the gap. After welding, grind and scrape the surface to align it with the surrounding area. If the deformation is large or leakage is severe, weld one or two 10–20 mm wide seals on the lower cylinder joint. Use a straightedge or a dial indicator to check and paint with red sand until the gap is eliminated. The process is simple: preheat the cylinder to 150°C before welding, perform segmented or back welding at room temperature, use austenitic electrodes like A407 or A412, and cover with asbestos cloth for slow cooling. After cooling, polish and scrape the surface.
**4. Coating or Spraying the Cylinder Bonding Surface**
When there is a large steam leakage area and a 0.50 mm gap, coating can reduce scraping workload. Electroplating involves using the cylinder as the anode and applying electrolyte solution repeatedly on the joint surface. The coating thickness depends on the gap size, and the material should match the cylinder’s composition and scraping process. Spraying uses a high-temperature flame gun to melt metal powder and spray it onto the treated surface, forming a durable coating without causing deformation. The temperature after spraying remains around 70–80°C, making it ideal for heat-resistant, wear-resistant, and corrosion-resistant applications. Before coating, the surface must be cleaned, degreased, and abraded. After application, scratch the coating to ensure tightness.
**5. Bonding Method**
For small gaps, use 80–100 mesh copper mesh, heat-treat it to reduce hardness, cut it to shape, and place it on the leak area with a sealant. For larger gaps, cut 50 mm deep and 5 mm wide grooves on both the upper and lower surfaces, insert an IGr18Ni9Ti toothed mat, and adjust with a stainless steel gasket.
**6. Bolt Stress Control Method**
If the deformation caused by bolt stress is small and even, replace the bolts or increase the preload. Tighten from the center outward, starting from the highest point of the vertical arc or the area with maximum deformation. Although theoretical calculations exist (d/L ≤ A), they are still under study and not widely used. Most rely on experience based on the bolt’s allowable stress.
**7. Modern Polymer Material Application**
With technological advancements, polymer composites are increasingly used in cylinder maintenance. Compared to traditional methods, they offer excellent thermal resistance, pressure resistance, and sealing performance. They remain pliable, do not cure when heated, and their sealing film doesn’t degrade. They are easy to remove using alcohol or acetone, leaving no residue. Due to these advantages, more companies are adopting them for cylinder sealing.
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