Common Oil Leakage Faults and Professional Treatment Solutions for Oil-Immersed Transformers
Oil leakage is one of the most common operational faults of oil-immersed transformers. Long-term oil leakage will lead to insufficient internal oil volume, reduced insulation performance, accelerated equipment aging, and even trigger safety hazards such as partial discharge and overheating. Combined with on-site operation experience, this chapter systematically sorts out seven typical oil leakage locations, analyzes root causes, and provides standardized professional maintenance and repair solutions.
1. Welding Point Oil Leakage
Fault Cause: The core cause of welding leakage is substandard welding quality. Defects such as false welding, desoldering, tiny pinholes and sand holes easily exist at the weld joints. During factory production, weld surfaces are covered with flux and paint, which conceal inherent welding defects. These hidden dangers gradually expose after long-term equipment operation. In addition, continuous electromagnetic vibration during transformer operation will cause secondary vibration and micro-cracking at weak welding positions, eventually resulting in oil seepage and obvious leakage.
Treatment Solution: First, comprehensively inspect all welding seams to locate all leakage points without omission. For severe and obvious leakage points, use flat shovels, sharp punches and other professional metal tools for local riveting to quickly reduce and control the oil seepage rate. After the leakage is temporarily controlled, thoroughly clean and polish the repair surface to remove oil stains, rust and impurities. Finally, adopt high-performance polymer composite materials for integral coating and curing. After complete curing, a dense protective sealing layer is formed to achieve long-term anti-leakage effect.
2. Structural Seal Oil Leakage
Fault Cause: The junction between the transformer tank body and tank cover relies on oil-resistant rubber strips or rubber gaskets for sealing. Poor construction and irregular joint treatment during assembly are the main causes of seal failure. Some on-site constructions adopt irregular fixing methods such as plastic tape binding or direct crimping of two joints. Due to uneven extrusion and incomplete fitting during installation, the sealing gasket cannot form effective compression and sealing force. Gaps appear at the joints after operation, leading to persistent oil leakage.
Treatment Solution: Adopt Fushi Blue special sealing material for joint bonding treatment to integrate the split joints into an integral sealed structure, which greatly eliminates gap leakage. For operating conditions with convenient construction space, synchronously bond and fix the metal shell joints to enhance overall structural tightness, completely solve seal failure leakage, and improve the long-term sealing stability of the tank body.
3. Flange Connection Oil Leakage
Fault Cause: Flange leakage is mainly caused by three abnormal factors: uneven flange surface flatness, loose fastening bolts, and non-standard installation procedures. Uneven flange planes lead to inconsistent stress on the sealing surface; incomplete bolt tightening and loose fastening force result in poor fitting of flange joints. All these defects will form tiny gaps on the sealing surface, causing slow oil seepage and continuous leakage.
Treatment Solution: Follow standardized operation procedures for maintenance. Firstly, uniformly tighten all loose flange bolts with standard torque to ensure balanced stress and complete fitting of the flange surface. After eliminating bolt looseness, perform overall sealing treatment on the flange joints. Meanwhile, conduct anti-leakage reinforcement on all bolt holes and potential leakage positions to achieve comprehensive and thorough leakage control and avoid repeated faults.
4. Bolt and Thread Interface Oil Leakage
Fault Cause: It is mainly derived from rough factory thread processing and insufficient initial sealing precision. After a period of sealed operation, the thread fitting gap changes due to vibration and temperature cycling, resulting in aging and failure of the original sealing layer, and finally causing oil leakage at bolts and pipe thread interfaces.
Treatment Solution: Two mature and reliable maintenance methods are adopted. The first method is to directly use high-performance polymer sealing materials for integral coating and sealing of bolt thread parts to block tiny gaps. The second method is to disassemble the bolts and nuts completely, evenly coat the thread surface with Fushi Blue release agent, then apply special sealing materials, reinstall and fasten them. After the materials are fully cured, stable and long-term thread sealing performance can be formed.
5. Cast Iron Component Oil Leakage
Fault Cause: Cast iron structural components of transformers are prone to inherent casting defects, including internal sand holes, trachoma gaps and microscopic cracks. Under long-term oil pressure and vibration, these tiny defects gradually expand and penetrate, resulting in oil seepage and leakage at cast iron parts.
Treatment Solution: Targeted treatment according to different defect types. For crack leakage, drill crack-stop holes first to release internal structural stress, prevent crack expansion and eliminate hidden dangers fundamentally. For on-site repair of cracks, embed lead wires or perform local hammer riveting at leakage points to block seepage gaps. All repair positions need to be thoroughly cleaned with acetone to remove oil stains and impurities, then sealed and repaired with special polymer materials. For independent sand hole defects in castings, direct material filling and sealing can be adopted to complete leakage treatment.
6. Radiator Oil Leakage
Fault Cause: Transformer radiator cooling pipes are manufactured by flattening and stamping seamed steel pipes. During the stamping and forming process, the pipe outer wall bears tensile force while the inner wall bears compressive force, resulting in residual internal stress. Bending sections and welding joints of cooling pipes are stress-concentrated areas, which are prone to micro-cracks and structural gaps under long-term oil pressure and vibration, causing radiator oil leakage.
Treatment Solution: Firstly, close the upper and lower butterfly valves of the radiator to isolate the internal oil circuit of the radiator from the transformer tank body, reduce internal pressure, and avoid oil overflow during construction. After accurately locating the leakage points, conduct professional surface polishing and decontamination treatment. Finally, use Fushi Blue high-strength sealing materials for targeted coating and curing to repair micro-defects and form a pressure-resistant and anti-leakage protective layer, realizing stable operation of the radiator.
7. Porcelain Bushing & Glass Oil Level Gauge Oil Leakage
Fault Cause: This type of leakage is mainly caused by non-standard installation technology and aging failure of sealing gaskets. The mismatched assembly gap and aging sealing materials lead to poor tightness between metal joints and porcelain/glass components, resulting in oil seepage at the interface.
Treatment Solution: Adopt high-performance polymer composite materials for repair. The materials have excellent bonding adaptability for metal, ceramic, glass and other heterogeneous materials, which can completely fit the interface gaps, form an integral sealed structure, fundamentally solve the leakage problem of porcelain bottles and glass oil markers, and ensure long-term stable sealing performance.
About us
Zhejiang Lvma Electric Co., Ltd. (founded 2018) leverages 17 years of electrical manufacturing know-how with ISO 9001:2015 certification. Our product portfolio centers on intelligent switchgear systems and extends to oil-immersed and dry-type distribution transformers. We export globally to Europe, the Middle East, South America, Southeast Asia, and Africa.
With over 40 patents, our R&D team is driving the company's transformation into a provider of smart, sustainable power solutions. Digital production processes and real-time condition monitoring ensure that every piece of equipment meets the highest standards of safety, reliability, and operational efficiency.