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Release time :
Jan 22,2026
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First, understand a key fluid dynamics concept—the boundary layer. According to Prandtl's boundary layer theory, when viscous steam flows over a blade surface, an extremely thin fluid layer forms near the wall.
First, understand a key fluid dynamics concept—the boundary layer. According to Prandtl's boundary layer theory, when viscous steam flows over a blade surface, an extremely thin fluid layer forms near the wall. This is the boundary layer. Within this layer, steam velocity gradually increases from zero at the wall surface to the main flow velocity. This velocity difference generates internal friction forces, causing energy loss. The thicker the boundary layer, the greater the loss.
Turbine blades are precision-polished at the factory to achieve an extremely high surface finish, effectively suppressing boundary layer thickening. However, during actual operation, salts and impurities carried by the steam deposit on the blade surface, forming scale. Simultaneously, steam impact and foreign object friction damage the surface smoothness. These changes cause the boundary layer to thicken rapidly and may trigger secondary flow losses, forming tip vortices that further consume unit energy.
I. Significance of Blade Cleaning
The surface condition of blades directly impacts the unit's economic efficiency and safety. Neglecting cleaning can lead to a series of problems:
In terms of efficiency, scaling and rough surfaces increase steam flow resistance and reduce the flow area. Data indicates severe blade scaling can cause up to 10% energy loss, significantly increasing thermal consumption rates and markedly reducing high-pressure cylinder efficiency.
Regarding safety, uneven salt accumulation causes blade weight imbalance, triggering rotor vibration. Acidic substances and dissolved oxygen beneath deposits corrode blades, while droplet erosion in wet steam zones damages blade bodies. Over time, this may lead to blade cracking, fracture, and severe accidents. Some power plants abandon cleaning based on visual assessments of minor scaling or resort to manual sandpaper cleaning. These methods fail to ensure adequate cleanliness and may scratch blades, creating latent hazards.
II. Cleaning Methods
The three mainstream blade cleaning methods—high-pressure water jetting, sandblasting, and shot blasting—each have distinct advantages and disadvantages. Selection should be based on operational conditions and scaling characteristics.
1. High-Pressure Water Jetting
Utilizes 20-28MPa high-pressure water jets to impact blade surfaces, removing deposits through stripping and shearing action. Advantages include no mechanical damage, access to hard-to-reach areas, and zero dust pollution. However, limitations are significant: metal surfaces are prone to rust post-cleaning, surface finish cannot be improved, and it is only effective for water-soluble salt deposits, offering limited results against stubborn contaminants.
2. Sandblasting Cleaning
High-pressure gas propels abrasives like sand to impact blades, offering high cleaning efficiency. However, the irregular edges of sand particles cause surface scratches during high-speed impact, damaging the metal microstructure. This process also generates significant dust, leading to secondary pollution. Furthermore, sandblasting provides only cleaning functionality without surface strengthening, gradually being replaced by shot blasting technology.
3. Shot Blasting
Similar in principle to sandblasting, but the core difference lies in the abrasive—shot blasting uses rounded glass beads (primarily silica) with no sharp edges. These beads have a controlled diameter of 0.25–0.35 mm and a hardness of 45–55 Mohs. When these spherical abrasives impact blades, they cause no scratches. Instead, they refine the surface microstructure through plastic deformation, enhancing surface finish and fatigue strength. This process improves corrosion and fatigue resistance by approximately 10%. Blades treated with shot peening achieve higher flow efficiency, offering a solution that combines cleaning with strengthening.
III. Common Misconceptions to Avoid
1. Reject “Visual Inspection Only”: Minor scaling is often invisible to the naked eye yet causes energy loss. Comprehensive inspection and cleaning are mandatory during overhauls; never omit steps based on experience.
2. Standardize Process Parameters: Strictly adhere to specifications for abrasive particle size, pressure, and angle during shot peening to prevent performance degradation from improper settings.
3. Implement post-treatment protection: After high-pressure water rinsing, use compressed air to dry blades to prevent rust. Promptly clean the work area after shot blasting and recover glass beads to eliminate safety hazards.
Though turbine blade cleaning may seem like a minor step in maintenance, it bears significant responsibility for ensuring efficient and safe unit operation. Selecting the right method and adhering to standardized procedures not only reduces energy loss but also extends blade lifespan, delivering substantial economic and safety benefits to power plants.
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