Introduction
The transformer tank, as the core protective structure of a power transformer, not only provides mechanical support, cooling, and insulation but also directly impacts the operational lifespan and safety of the transformer through its manufacturing precision and reliability. With the evolution of power systems toward higher voltage, larger capacity, and smarter functionality, the design and manufacturing of transformer tanks face increasingly stringent technical requirements, such as lightweight construction, corrosion resistance, and enhanced sealing performance. This article systematically analyzes the material selection, structural design, and detailed manufacturing processes (including key steps such as cutting, welding, and leak testing) of transformer tanks, while also exploring the latest industry trends to serve as a reference for transformer manufacturing and maintenance.
Functions of the Transformer Tank
The transformer tank is the primary external structure of a transformer, serving several critical functions:
1. Containment and Protection: Houses the transformer core (iron core, windings, etc.) and insulating oil, shielding them from external contaminants (dust, moisture).
2. Cooling and Insulation: Facilitates oil circulation for heat dissipation through tank walls and radiators (or corrugated panels); the insulating oil also provides electrical insulation.
3. Mechanical Support: Bears the weight of the internal components and electromagnetic forces during short-circuit events.
4. Safety Measures: Features a sealed design to prevent oil leakage, with some tanks incorporating explosion-proof devices (e.g., pressure relief valves).
Additional Insight: Modern transformer tanks must also meet environmental requirements, such as fully sealed designs to minimize oil-air contact and slow oil degradation.
Materials for Transformer Tanks
The choice of materials for transformer tanks depends on factors such as operating environment, durability, and cost. Below are the most commonly used options and their characteristics:
Mild steel
Mild steel is the most widely used material due to its high strength, affordability, and ease of fabrication. It can withstand the internal pressure caused by thermal expansion of insulating oil. Surface treatments (e.g., painting or coatings) are often applied to enhance weather resistance, making it suitable for outdoor installations.
Stainless Steel
In corrosive environments (e.g., coastal areas, chemical plants, or high-humidity regions), stainless steel tanks are preferred. Their superior rust resistance extends service life and reduces maintenance needs, though at a higher cost.
Alternative Materials
- Galvanized Steel: Offers improved corrosion resistance through zinc coating, balancing weight and cost.
- Aluminum: A lightweight option, but requires careful consideration of strength and oil compatibility.
Additional protective layers or insulation may be applied to tanks for extreme weather or chemical exposure.
Typical Tank Structures
1. Tank Body Designs:
o Flat-Top Tanks: Used in small transformers for simplicity.
o Arched-Top Tanks: Common in medium/large transformers, with a curved top for enhanced pressure resistance.
o Corrugated Tanks: Feature wave-like walls to adjust oil volume via thermal expansion (maintenance-free design).
2. Attachments:
o Cooling Systems: Welded cooling pipes, detachable radiators, or corrugated panels.
o Flanges and Sealing Surfaces: For mounting bushings, oil gauges, and valves.
o Reinforcing Ribs: Prevent deformation, usually on sidewalls and base.
o Lifting Lugs and Trailers: Aid transportation and installation.
SCOTECH – Professional Manufacturer of power Transformer oil tanks
SCOTECH is a professional manufacturer of high-quality transformer tanks, offering a comprehensive range of solutions for various transformer applications. Our product lineup includes:
Designed for compact, ground-mounted single-phase transformers, ensuring durability and efficient heat dissipation.
Robust construction for three-phase pad-mounted units, suitable for utility and industrial use.
Lightweight yet sturdy tanks optimized for overhead pole-mounted single-phase transformers.
Engineered for reliability in three-phase pole-mounted applications, with excellent weather resistance.
Heavy-duty tanks built to withstand high-capacity substation demands, ensuring long-term performance.
Efficient and cost-effective designs for reliable power distribution networks.
Heavy-duty design for large-capacity, high-voltage transformers, featuring robust construction, superior cooling performance, and long-term reliability. Customizable to meet specific insulation and cooling requirements.
Tailored solutions for unique or specialized transformer requirements. (traction transformer, furnace transformer, rectifier transformer, earthing transformer).
SCOTECH’s transformer tanks are manufactured with precision, using high-grade materials to ensure superior corrosion resistance, structural integrity, and optimal thermal management. Whether for standard or custom applications, we deliver tanks that meet global certifications and customer-specific needs.
Detailed Manufacturing Process
1. Cutting
o Laser/Plasma Cutting: High-precision steel plate cutting with welded edge beveling (e.g., V-grooves).
o Quality Control: Inspect for burrs and flatness to avoid welding defects.
2. Drilling
o CNC Drilling: For flange and fastener holes (tolerance ≤0.5 mm to ensure sealing).
o Deburring: Remove sharp edges post-drilling.
3. Bending and Rolling
o Press Brake: Forms right-angle bends (e.g., side panels); bend radius ≥2× material thickness to prevent cracks.
o Rolling Machine: Shapes arcs for arched/corrugated tanks, ensuring circularity accuracy.
4.Cylinder Rolling Process
Utilizes high-precision plate rolling equipment and strict curvature control to ensure tank roundness error <0.2%.
5.Welding
o Methods: Submerged arc welding (long seams), CO₂ gas-shielded welding (complex joints).
o Inspection: X-ray or ultrasonic testing for critical welds.
6.Grinding and Slag Removal
o Angle Grinding: Smooth welds flush with the base metal.
o Sandblasting: Cleans oxidization (Sa2.5 standard) for coating adhesion.
7.Comprehensive Slag Removal Process
• Multi-stage cleaning system (mechanical + chemical)
• 100% weld seam inspection and slag removal
• Ultrasonic testing for hidden defects
8. Leak Testing
o Pressure Test: 0.03–0.05 MPa for 24 hours; detect leaks with soap solution or helium.
o Vacuum Test: Evacuate to <133 Pa to verify sealing.
9.Surface Treatment
a) Powder Coating/Painting: Epoxy resin (80–120 μm), baked; UV-resistant coatings for outdoor use.
b) Interior Treatment: Insulating varnish or passivation to prevent oil contamination.
Advanced Techniques and Trends
1. Corrugated Tank Innovations:
o Hydroforming: Molds steel into waves, optimizing depth/spacing for cooling.
o Fatigue Testing: Simulates thermal cycles (≥100,000) for durability.
2. Eco-Designs:
o Coating-Free Options: Weather-resistant steels (e.g., Corten).
o Modular Tanks: Disassemblable for recycling.
3. Smart Manufacturing:
o Robotic Welding: Vision-guided for precision.
o Digital Twins: Simulate strength and thermal performance.
Design Requirements for Transformer Tank
1. Material and Shielding: The tank shall be constructed from high-strength steel plates through welding, with internal magnetic shielding to reduce stray losses. The magnetic shielding must be securely installed and well-insulated to prevent overheating or discharge caused by poor contact. All electric shields shall exhibit excellent conductivity and reliable grounding to avoid floating discharges or impacts on the dielectric loss factor of windings.
2. Top Structure: The tank top shall be sloped to facilitate drainage and direct gas accumulation toward the gas relay. All openings on the top shall be equipped with raised flanges. Vent plugs shall be installed at the highest points of any potential air pockets, connected via a common pipeline to the gas relay. Additional collector pipes shall be added to the high- and medium-voltage bushing risers, linking to the pipeline between the tank and the gas relay. The pipeline to the gas relay shall have a 1.5% slope. The gas relay must include rainproof measures, with its sampling pipe extended to the ground.
3. Base Design: The exterior of the tank bottom shall feature a channel steel base frame, enabling the transformer to be dragged along its longitudinal and transverse axes. The base shall include towing devices and anchoring systems with foundation bolts to secure it to a concrete base, capable of withstanding inertial forces from the equipment’s weight and seismic displacements. The manufacturer shall submit bolt and fixing details for approval by the operating entity.
4. Segmented Construction: The tank shall adopt a two-section assembly design. If welded, reusable flanges and sealing gaskets must be employed to ensure airtightness.
5. Grounding Measures: Two grounding terminals shall be installed diagonally at the tank bottom. The primary purpose of tank grounding is personnel safety-should transformer insulation fail, leakage current will be diverted to the ground via the grounding system, preventing electric shock hazards.
Requirements for Transformer Tank Grounding System
1. Grounding Terminals
o At least two grounding terminals shall be installed diagonally at the tank bottom.
o Terminals should be made of galvanized steel or copper to prevent corrosion.
2. Grounding Conductor
o Use multi-strand copper cable or galvanized flat steel with sufficient cross-section to withstand fault currents.
o Minimum cross-section: 50mm² (copper) or 100mm² (steel) per national standards (e.g., GB/T 50065).
3. Grounding Resistance
o Grounding resistance must be ≤4Ω (per power system regulations).
o In high-resistivity soil, use ground enhancement materials, deep electrodes, or additional rods to reduce resistance.
4. Connection Method
o Terminals and conductors should be bolted or welded for low-impedance contact.
o If bolted, lock washers must be used to prevent loosening due to vibration.
5. Corrosion & Mechanical Protection
o Grounding components should be hot-dip galvanized or painted for corrosion resistance.
o Buried electrodes should be protected by PVC pipes or angle steel if exposed to mechanical stress.
6. Connection to Main Ground Grid
o The tank must be directly connected to the main grounding grid (no series connections).
o Grounding path should be short and straight to minimize impedance.
7. Inspection & Maintenance
o Regularly measure grounding resistance to ensure compliance.
o Check for loose, corroded, or broken connections and repair promptly.
