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The Reasons & Prevention Methods of Oil Leakage in Oil-immersed Transformer Oil Tank

April 16, 2019

Oil-immersed Distribution Transformer Oil Tank leaks oil affect the using of power transformer. This Article stated: Why the Oil-immersed Transformer Tank leaks oil? How to prevent transformer tank leaks oil?

Why the Oil-immersed Transformer Oil Tank leaks oil?

Distribution Transformer Oil tank and parts mostly use 4-12 mm steel plate. Such as the wall, bottom, hand hole, elevator, oil storage tank, some Transformer Tank Manufacturers use double-sided welding (no groove or no groove), so that there is a gap between the inside and outside welds of the tank.

Sometimes this gap extends very long, and there is a micro-pore or other defect leakage point on the inside and outside welds. Some of the two holes are far apart, so it is difficult to find them by using the existing leak test methods. When transformer oil is filled, a narrow and long oil passage is formed, which is difficult to find.

In theory, transformer oil tank leakage detection methods include:air pressure, water pressure, oil pressure leakage test, coloring test, fluorescence test, ultrasonic test and so on. However, for large transformers with many welds and large volume, many methods have limitations in use, considering the limitations of equipment, site, cost and so on.

Air pressure leakage test advantages:

Comparing comprehensively, (Air pressure)pneumatic leak test is the most effective and widely used method. It is easy to operate, leak detection is convenient and practical, and low cost. Therefore, this method is widely used by most manufacturers. But for the narrow and long passages between the internal and external welds mentioned above, it is very difficult to detect the leakage by air pressure test (the same is true for water pressure and oil pressure test).

Transformer Tank Corrugated Finwall is adopt Air pressure /Pneumatic leak test method by JTFY corrugated fins wall leakage test machine.

corrugated fins wall leakage testing machine

corrugated fins wall leakage testing machine

For corrugated wall structure transformer oil tank, because the
cold rolled plate is thin. If the manufacturing process is not well mastered, it will increase the leakage point. Especially the fin height of corrugated fins and the fixed circular steel can not exist stress, otherwise it will cause jump cracks in transportation.

As the development of Welding technology, Automatic Welding machine is designed and used in the manufacturing of Corrugated Fins Wall Seam Welding. JTFY PLC Automatic Corrugated Fins Wall Welding Machine, is the best quality welding machine. Corrugated Fins height, Welding seam length can be set by PLC. Whole welding process is full automatic. Welded Fins Wall seam is smooth,quality is good.

automatic transformer radiator corrugated fins welding machine

automatic transformer radiator corrugated fins welding machine

good welded Corrugated fins wall

good welded Corrugated fins wall

The latent oil leakage means that it is difficult to check the leakage defects under the usual leak test methods. In fact, there is a leakage source in the weld, which leads to the leakage of transformer after a period of time. The leakage exposure time depends on the size of the defect, the width of the oil pipeline and the oil pressure in the tank. Some may be found half a month or a month later, and some may be found half a year or a year later. If there are many latent oil channels, it will appear at different times, and it is difficult to repair welding at one time.

How to prevent transformer tank leaks oil?

1.Improving Welding Quality of Transformer Oil Tank

Oil tank manufacturer should select some employees with good welding skills and responsible old staff to engage in welding work. The leakage points of weld seam of corrugated oil tank mainly occur in:

  • Bottom of corrugated wing side wall
  • Corruagted Fin Wall and Transformer tank Bottom
  • The Joint of Welding Seam

In addition, there are three reasons for transformer tank leakage:

1. Because the plasma welding seam on the wavy wing side is not welded to the end or there is a big gap in the bottom of the welding seam.

2. The coverage width and height of the weld seam on the wave wall side are insufficient.

3. This position is the fulcrum of the wave-wing cantilever, and the stress is large. When the transportation condition is poor and the weld strength is insufficient, it is easy to crack and leak.

Generally speaking, the main reasons are low welding level and low sense of responsibility. It is suggested that oil tank manufacturers order vibration aging equipment to ensure that the post-weld aging process of oil tank will be increased in the manufacturing process, and that vibration welding process should be adopted in the welding process to increase the welding quality. Vibration stress relief instrument is used to improve the welding quality of oil tank after welding.

2.Improving the quality of leak test

Oil tank leakage test determines the quality of transformer, so oil tank leakage test is the key.

Preparations before leak test: cleaning welding slag

Vertical welding or up welding of arc welding is difficult to clean because of slag inclusion. Therefore, special attention should be paid to cleaning up carefully. A weld slag of 0.5mm_may cause a defect to be missed due to blocking the gas holes. Soap water with 8% concentration can be used as leak detection material. In this way, leakage can be found more clearly.

Whole transformer tank leak test:

transformer tank leakage test

transformer tank leakage test

After sealing the transformer tank, pressurize it to the standard pressure (the pressure of corrugated plate tank is less than 30 kP; the pressure of sheet radiator tank is less than 55 kP). After holding pressure for 30 minutes, soap water is used for the first leak test. After the inspection of all welds, if there are leaks, the gas is released to repair the welding, and then the pressure is re-pressurized to the original pressure, holding pressure for more than 12 hours, so that the high-pressure gas can fully penetrate into the narrow and long gap, and then conduct a second leak test, so that the leakage source can be more thoroughly detected.

Transformer Corrugated Cooler Wall Manufacturing Related Machines:

Automatic Corrugated Fins Wall Manufacturing Line

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Corrugated Fins Wall Forming Machine

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corrugated fins wall making machine

corrugated fins wall making machine

Full-auto PLC Corrugated Fins Seam Welding Machine

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corrugated fins wall seam welding machine

corrugated fins wall seam welding machine

Hydraulic Decoiler

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steel roll feeding machine

steel roll feeding machine

Corrugated Fins Wall Leak Testing Machine

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corrugated fin wall leakage test machine

corrugated fin wall leakage test machine

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