Case Study: Yazd Power Plant Inner Casing Refurbishment
In today’s world, where the demand for electricity is constantly increasing, power plants play a key role in meeting this need. Proper maintenance of these facilities is essential to ensure their stable and optimal performance. One of the critical components of gas turbines is the inner casing, whose repair and reconstruction are of great importance. This report provides a detailed overview of the key stages involved in the reconstruction of this component at the Yazd power plant, carried out by the technical team of Paya Mavad Company.
What Is the Inner Casing and Why Is Its Reconstruction Important?
The inner casing is one of the vital components of gas turbines, operating under extreme conditions such as high temperatures, severe mechanical stresses, and corrosive environments. This part has a direct impact on the safe and efficient performance of turbines. Therefore, regular inspections and specialized repairs are essential to enhance its lifespan and functionality.
Stages of Inner Casing Reconstruction – From Evaluation to Delivery
1. Initial Inspection and Assessment
The reconstruction process began with a thorough examination of the component. During this stage:
- Damages such as cracks, corrosion, and other signs of degradation were identified.
- Compliance with design standards and technical specifications was checked.
This step served as the foundation for deciding the appropriate reconstruction strategy.
2. Identification of Degradation Mechanisms
The operational degradation mechanisms affecting the component were analyzed, including:
- Creep and oxidation
- Hot corrosion and thermal fatigue
These analyses played a crucial role in selecting the most effective restoration methods.
3. Material Examination
The alloy used in the component, Incoloy 800, was carefully evaluated. Key properties of this alloy include:
- High resistance to elevated temperatures
- Excellent corrosion resistance
Understanding these properties enabled the implementation of optimized repair techniques.
4. Repair and Reconstruction
Following the assessments, the reconstruction phase began:
- Surface cleaning using techniques such as sandblasting
- Specialized welding to repair cracks and ensure structural integrity
- Dimensional correction based on the component’s technical specifications
- Heat treatment to relieve stress and enhance mechanical properties
5. Quality Control
Multiple tests were carried out to ensure the quality of the reconstruction:
- Thickness testing using ultrasonic methods
- Mechanical tests such as tensile and creep tests
- Non-destructive testing (NDT) including dye penetrant inspection
6. Evaluation and Remaining Life Estimation
After reconstruction, a detailed analysis was conducted to estimate the component’s remaining service life. This was achieved through computational models and performance testing.
7. Delivery and Warranty
Upon completion of all steps, the refurbished component was delivered with a warranty, which included:
- Defined duration: 12 months
- Equivalent operating hours: 8,000 hours
Technologies Used in the Reconstruction of the Inner Casing
Effective reconstruction of the inner casing requires the use of advanced technologies and specialized equipment in the fields of surface engineering, industrial welding, precision machining, and quality inspection. At Paya Mavad, the process is carried out with a high level of precision and quality, backed by up-to-date engineering expertise and modern equipment.
1. Specialized Welding with Heat- and Corrosion-Resistant Alloys
One of the critical stages of reconstruction involves repairing cracks, erosion, and damaged areas using welding techniques with electrodes or filler wires compatible with the base alloy. In this project, TIG and SMAW welding technologies were used, with controlled pre-heating and post-heating to prevent residual stress formation.
2. Precision CNC Machining After Reconstruction
After the welding and repair operations were completed, all critical surfaces of the inner casing were precisely machined using CNC equipment to restore the component’s geometry to its original or design-standard specifications.
3. Metallurgical Analysis and Non-Destructive Testing (NDT)
To evaluate the repair quality and ensure the structural integrity of the component, several tests were conducted, including:
- Penetrant Testing (PT)
- Magnetic Particle Testing (MT)
- Ultrasonic Testing (UT)
- Radiographic Testing (RT) (in critical areas)
In addition, samples were prepared for microstructural analysis to inspect weld quality and detect any cracks or discontinuities.
4. Static and Dynamic Balancing
For parts of the inner casing that involve rotational movement or directly affect the turbine’s balance, balancing operations were carried out using dedicated equipment. This prevents excessive vibration and premature wear of the components.
5. Reverse Engineering and 3D Modeling Software
In cases where engineering drawings were not available, the technical team at Paya Mavad used 3D scanning and CAD/CAM software to recreate the engineering model of the component and design the reconstruction process accordingly.
High-Quality Materials in the Inner Casing Reconstruction Process
The use of high-grade materials is a key factor in the success of the reconstruction process. In industrial applications—especially in gas turbines—the inner casing is subjected to extreme heat, mechanical stress, and corrosion from harsh operational conditions. Therefore, selecting the right material ensures durability, safety, and high performance after repair.
Key Characteristics of the Materials Used:
- High resistance to heat and oxidation
- Full compatibility with the base alloy
- Excellent weldability and minimal residual stress
- High durability in power plant working conditions
At Paya Mavad, the materials used for welding, coating, and repairing the inner casing are selected based on detailed metallurgical analysis and in compliance with international standards. This engineered selection ensures that the reconstruction restores not only the appearance but also the performance of the component.
Advantages of Inner Casing Reconstruction by Paya Mavad
Reconstruction of the inner casing by Paya Mavad’s specialized team provides a valuable and professional solution for power plants and turbine-based industries for several technical, economic, and operational reasons.
Main Advantages:
- Reduced Capital Costs:
Professional reconstruction instead of purchasing new parts leads to significant cost savings. - Extended Service Life:
High-quality materials and rigorous quality controls guarantee a renewed lifespan for the inner casing. - Minimized Downtime:
The reconstruction process is completed in a shorter time compared to sourcing new components from abroad, thus reducing power plant outages. - Localization of Technical Knowledge and After-Sales Services:
Paya Mavad leverages skilled local engineers and offers ongoing technical support after delivery. - Compliance with International Standards:
All reconstruction steps—from inspection to final quality control—are conducted according to internationally recognized standards such as ASME and API.
Conclusion
Reconstruction and optimization of power plant components play a vital role in ensuring the stable and efficient operation of energy systems. The inner casing reconstruction project by Paya Mavad is a clear example of commitment to quality and the effective use of advanced technologies. This process not only serves as a model for similar projects but also highlights the importance of effective management and utilization of existing resources.
