Vacuum Nitrogen Drying Equipment: Nitrogen instead of Air

The new process of HEDRICH uses nitrogen instead of air for the drying operation. Thus, higher drying temperatures can be reached. Your benefit: The drying times are significantly reduced. The conventional technology using air as heat transferring medium has the disadvantage that the drying temperature needs to be limited because of the existing atmospheric oxygen in order to avoid excessive depolymerization.

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Through the use of nitrogen as heat transferring medium, the process happens without exposure to oxygen. This allows higher temperatures, faster heating times and a significant reduction of the depolymerization rate of the insulation.

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Higher Temperatures

The use of nitrogen allows to increase the drying temperature by 20°C so that the drying times can be significantly reduced. The effectivity and productivity of the equipment can be considerably increased.


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Auto-Adaptation of Process

Thanks to the optimized process steps, the drying time is reduced. After the specific transformer data have been entered, the process control unit selects the optimum program and, by means of different sensors, optimizes the duration of the intermediate pressure reductions, the exchange of the nitrogen saturated with water vapour as well as the fine vacuum phase.


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Ideal for Retrofit

Not only new drying systems can be equipped with the innovative drying by nitrogen, a retrofit is also possible on existing vacuum hot air drying systems. A modular concept guarantees fast retrofitting including optimization of the control with auto-adaptation of the process.


Advantages of vacuum nitrogen drying equipment

• 30 -40% shorter drying times compared with the vacuum hot air drying equipment
• 15-20% higher drying temperatures
• Optimization of existing conventional HEDRICH vacuum hot air drying equipment
• Minor depolymerization of the insulation paper
• Energy-efficient equipment concept
• Auto-adaptation to optimally adjust the drying process to the batch size
• Minimization of the nitrogen to be exchanged to save energy
• Online registration of dew point and water rate during the fine vacuum phase


• Distribution transformers
• Power transformers
• High-voltage instrument transformers
• High-voltage bushings
• Components for transformers
• Transformer windings
• Traction transformers

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