Surface coating Technologies

Erosion-Major problem faced by Hydro Powder Industries.
Erosion and cavitation is the most critical problem effecting under water parts of Francis, Pelton and Kaplan turbines installed in hydro plants. Components other than turbine located under water are also affected. Erosion is caused by the silt load that passes through the underwater parts and components. The severity of erosion is dependent on the geographical location of the power plant. The fragile geographical conditions and steep mountain slopes add to the constant erosion and land slide. The mountain scape contributes to the heavy silt load that passes through the underwater turbine parts and components creating substantial surface damage. During monsoon the silt concentration is compounded and adds to the damage of the under water parts. A large part of the silt load consists of hard particles like silica & quartz.

Turbine Parts and other underwater components affected by erosion.
The result of heavy silt related damage in the form of erosion and cavitation is found in the following turbine parts.

• Runners
• Cheek Plates
• Guide vane bushes
• Guide vanes
• Labyrinth seals
• Guide vane sleeves.

In addition to turbine parts other components vulnerable to silt damage are seals of the gates.

• Inlet gates
• Sft gates
• Radial gates
• Draft tube gates.

Damage to seals is very prominent and regular replacements/refurbishments are required. Lip of radial gates and sft gates are also affected by silt load especially after snow melt and high flow season.

Role of ATS in Hydro Power.
ATS obtained ISO 9001 – 2000 certification and all aspects of Thermal Spray coating business operate under ISO accreditation.
Full fledged workshop with setup of advance HVOF system, Vacuum Blasting machines, latest turn table for job mounting, the coating is done by ROBOT in specially designed spray chamber for better coating quality.
Our technical staff is well trained and experienced to provide services at site, in-situ and at our job shop in Ahmedabad.

Reduced Efficiency of Hydro Power Plants
The erosion caused by the heavy silt load that presses through the underwater components of hydro plants results in reducing the working efficiency of turbine parts and components. This leads to reduction in productivity of the power plants. Silt Erosion also leads to heavy repair cost, machine down time and decrease in overall productivity of the plant. Turbine parts can be easily inspected for damage when required, however there are other components like silt beam for the gates, discs for the B/F valves, pressure shafts which are also prone to damage by silt conditions.
These components can only be inspected by making elaborate arrangement which require long period of shutdown, leading to heavy cost and reduced efficiency of the power plant. Hence there is a serious need to find methods for protecting and enhancing the life of underwater parts.

Research and development by ATS to prevent erosion.
To combat the problem of surface damage silt resistant protective coatings have to be applied to turbine parts. Our research team has developed specially formulated coating materials and coating processes for surface coatings of turbine parts and extending their working life. Several Thermal Spray methods has been considered for surface coatings and HVOF (High velocity Oxyfuel) process has proved to be appropriate and most successful. Many samples of turbine parts and components were coated by HVOF with different process parameters to arrive at the right solution. Combination of tungsten carbide powder are used in HVOF as these powders are characterized by high hardness, excellent bond strength and wear resistance properties.