What Are Hermetically Sealed Oil Transformers?
Hermetically sealed oil transformers are static electrical machines designed without a conservator tank, ensuring the dielectric insulating oil is completely isolated from the atmosphere. This sealed architecture prevents oil oxidation and moisture absorption, preserving insulation properties. The design accommodates oil expansion and contraction through the elasticity of the corrugated tank fins. These units provide superior reliability and require virtually zero maintenance compared to conventional breathing transformers.
Comparing Hermetically Sealed vs. Conventional Transformers
Oil Preservation
- Hermetically Sealed: The oil never comes into contact with the atmosphere, preventing oxidation and sludge formation. The dielectric strength remains high indefinitely.
- Conventional: The oil “breathes” through a conservator, leading to moisture intake and oxidation, which degrades insulation over time.
Maintenance Requirements
- Hermetically Sealed: Virtually maintenance-free. No need to monitor oil levels, change desiccants, or test oil quality regularly.
- Conventional: Requires regular inspection of the breather (silica gel), frequent oil sampling, and potential oil filtration or replacement.
Safety and Installation
- Hermetically Sealed: Safer for hazardous locations due to the sealed tank. The corrugated fins provide efficient cooling and flexibility.
- Conventional: Higher risk of leaks and requires more vertical clearance due to the conservator tank assembly.
Technical Specifications of Hermetically Sealed Oil Transformers
| Feature | Specification |
|---|---|
| Rated Power | 50 kVA up to 5,000 kVA |
| Primary Voltage | Up to 36 kV |
| Secondary Voltage | 400V - 433V (Customizable) |
| Frequency | 50 Hz / 60 Hz |
| Cooling Method | ONAN (Oil Natural Air Natural) |
| Vector Group | Dyn11, Yyn0 (Others on request) |
| Tap Changer | Off-circuit tap changer (±2 x 2.5%) |
| Insulation Liquid | Mineral Oil (PCB free) or Ester Oil |
| Ambient Temperature | -25°C to +40°C |
| Corrosion Protection | C3, C4, or C5-M coating classes available |
Why Choose Our Hermetically Sealed Oil Transformers
Extended Equipment Lifespan
By completely preventing contact between air and oil, we eliminate oxidation and sludge formation, significantly prolonging the transformer’s operational life.
Minimized Maintenance Costs
With no breather, silica gel, or conservator tank to maintain, our units offer a “fit and forget” solution that drastically reduces O&M budgets.
Enhanced Safety Features
Our robust sealing technology reduces the risk of leaks and includes integrated protection devices to monitor pressure and temperature for safe operation.
Eco-Friendly Design
The sealed tank prevents oil leakage into the environment, and our efficient core designs reduce energy losses, lowering your carbon footprint.
Tailored Customization
We don’t believe in one-size-fits-all. We engineer solutions to meet specific voltage, power, and dimensional requirements for your unique project.
Compact Footprint
The absence of a conservator tank allows for a lower profile and more compact design, making these units ideal for indoor substations or space-constrained areas.
Applications of Hermetically Sealed Oil Transformers
Industrial Manufacturing
Perfect for harsh industrial environments involving dust, humidity, or chemical exposure.
Indoor & Underground Substations
Their compact height and high safety profile make them the preferred choice for basement or limited-space installations.
Oil & Gas Platforms
Designed to withstand hazardous zones with robust sealing that prevents combustible gas interaction.
What Our Clients Say
“We switched to these hermetically sealed units for our offshore facility. We haven’t had to touch them since. The reduction in maintenance hours has been a massive cost-saver for our operations.”
David Chen
Operations Director
“The customization options were exactly what we needed. We had a very tight space in an urban substation, and their engineering team designed a unit that fit perfectly without compromising on power rating.”
Sarah Jenkins
Project Engineer
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Frequently Asked Questions (FAQs)
The tank walls are constructed with corrugated flexible fins. As the transformer heats up and the oil expands, these fins flex outwards to increase the tank’s internal volume. When the oil cools and contracts, the fins return to their original position, keeping the system balanced without external air.
Due to the prevention of oil degradation (oxidation) and the exclusion of moisture, these transformers typically last significantly longer than conventional types. You can expect an operational lifespan of 30+ years with proper loading and environmental conditions.
Yes, but it requires specialized handling. Since the unit is sealed under vacuum or with a gas cushion, any repair involving the tank wall usually requires the unit to be taken to a workshop where it can be properly drained, repaired, refilled, and resealed to ensure the hermetic integrity is restored.
Absolutely. They are actually preferred for indoor use. Because they lack a conservator tank, they are shorter, fitting easily into rooms with lower ceilings. Additionally, the sealed design reduces the risk of oil leaks and fire hazards, making it safer for enclosed spaces.
Safety is paramount. Every unit is fitted with a pressure relief valve. In the unlikely event of a massive internal fault causing a rapid pressure spike, this valve opens to release the pressure safely, preventing the tank from rupturing.
Yes. We offer customization options, including special paint finishes (C4/C5 corrosion protection) for marine environments, high-temperature fluids for hot climates, and specific terminal box arrangements to suit existing cabling infrastructure.
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