Vacuum Transformer Drying Ovens

The HERING Drying Series vacuum transformer drying ovens focus on bringing down the drying time of your transformers by combining the best state-of-the-art technologies for the benefit of your operations.
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HERING has specialized in improving the life cycle of transformers. This starts during the transformer manufacturing process. The right transformer drying solution provides a low process time, but also protects the equipment from high internal stresses. Here, the HERING Drying Series product line offers state-of-the-art technology to speed up your transformer manufacturing operations.

During the later life cycle of the transformer, not only drying the insulating oil extends the lifetime, but also drying the insulating material has a significant positive impact. For the latter, the HERING Drying Series – our product line of state-of-the-art vacuum transformer drying ovens – is your ideal choice.

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HERING VPT offers the right equipment for every application, in order to ensure an optimal price-performance ratio. There are generally three types of transformer drying systems depending on the process used:

≤ 100 MVA: Hot-Air Drying Plant for easy setup

> 100 MVA: Vapour-Phase Drying Plant for reduced process duration

Low frequency electric heating vacuum transformer drying technology

In any case, HERING VPT will help you to choose the right process for your specific application.

HERING Systems are remarkable for their compact and robust design, as well as their ease of operation and maintenance.

The complete drying plants are divided in sub modules. Each module, e.g. heating station or kerosene station, is completely piped, wired and pre-tested in our workshop. This concept convinces with a fast, easy and safe installation of the plant. Additionally, the customers have the opportunity to set up the complete plant by themselves.

Are you rather interested in transformer oil purification plants for a maintenance oriented treatment of your transformer? Then, our Hering EOK Series Vacuum oil purification plants might be the right choice for you.

Do you want an even more advanced overhaul of your transformer oil? Then, our HERING EOK-TORS Transformer oil regeneration systems are the best solution for you. These systems combine the strengths of our EOK Series transformer oil purification plants with the added functionality of an oil polishing system.

Still not found what you were looking for? Take a look at our products page for our most popular products or get in touch for customized solutions. We will build the right product for you!

Vacuum Transformer Drying Ovens

The complete drying plants are divided in sub modules. Each module, e.g. heating station or kerosene station, is completely piped, wired and pre-tested in our workshop. This concept convinces with a fast, easy and safe installation of the plant. Additionally, the customers have the opportunity to set up the complete plant by themselves.

The complete drying plants are divided in sub modules. Each module, e.g. heating station or kerosene station, is completely piped, wired and pre-tested in our workshop. This concept convinces with a fast, easy and safe installation of the plant. Additionally, the customers have the opportunity to set up the complete plant by themselves.

General Specification

The system is designed for drying of transformer active parts

Engineering

  • Foundation plan
  • Main oven drawing
  • General floor plan

Chamber - Usable Inner Dimensions.

The vacuum chamber is a welded design. The vacuum-tight, rigid and smooth inner wall is made of plate. The plate walls are reinforced at the outside by attached and welded profiles. The vacuum chamber is designed for a temperature of 200°C. Working temperature: 20-120 ° C. One side of the chamber is equipped with a door flange. The support frame of the Viton door sealing is welded onto the flange.

Door

The vacuum chamber is equipped with one large door. The door opening cycle begins with door lifting and after it the door makes a rotating movement. The fixation enables an elliptic movement to reduce the required space. The lifting of the door is insured by a hydraulic jack working with a hydraulic central. The rotating movement is automatic

Or

The vacuum chamber is equipped with one large door. The doors will be opened side wards with trolley system which are installed at a stable horizontal beam. The closed doors pushed against the chamber by hydraulic cylinders. End switches controls the closing way of these cylinders. The necessary hydraulic aggregates are included in the scope of delivery. The door is equipped with an operating board with push buttons and signals for the activation of the door. Additionally, the operating board is equipped with an emergency switch and a key switch.

Technique Platform Delivery

All followed mentioned items will be delivered assembled on one base plate, piped, wired, isolated and tested in our work shop in Germany

Heating of Camber

Heating by electric energy

Wall Heating - The inside walls of the chamber are equipped with a heating system of tubes. The heating system is covered by detachable steel sheet panel which will be also used for air guiding during circulation.

  • Electrical oil heater will be delivered
  • Heating capacity about 200 KW
  • Heat transfer oil circulating pump station
  • Air cooled including motor and base plate.
  • Pumping head: 4,5 bar
  • Door heating
  • Electrical heating elements will be installed.

Heat Insulation

On the outside the chamber is surrounded by a heat insulation out of rock wool. The insulation plates are 120 mm thick and are covered by galvanised sheeting. The bottom of the oven is insulated by a plate 25 mm thick of compressed rock wool plates The doors are insulated also with insulation plates, 120 mm thick

Hot Air Circulation System

In the cover of chamber exhausters are installed. The motors are outside and con-nected to the impellers by vacuum tide feed through to the inner side of chamber. The feed through and shaft of exhauster are water cooled. Inside the chamber is the roof and all side are designed as an optimized air channel system. In side of air channel heating pipes are installed. During heating process the air will circulated from impeller pass air channel systems where heating pipes are installed and will be heated up. When this hot air is passing the active part it will transfer the heat to the active part in order to heat it up and air will be cool down.

Fresh Air Inlet

The system is equipped with a pneumatically operated fresh and waste air motor valve for the hot circulation in the chamber. The fresh and waste our valve are opened automatically, when the ventilators for the air circulation are switched on. The outer piping leading to the fresh air inlet and outlet valve is not included in the scope of delivery.

Temperature measurement

Thermo elements inside the chamber are measuring the temperature directly at the transformer (one piece per transformer). The control and regulating of the temperature is done by the PLC which is built in the switch cabinet. The figures and values will be shown and controlled by the Con-trol program of the PC.

Vacuum equipment

The vacuum system is installed beside the chamber. The vacuum system is connected to the chamber by a tube system. The connection flange to the pumping unit is located at the chamber side wall. The chamber is separated from the pumping unit by an automatic activated valve.

Vacuum pumping station consisting of:
For smaller oven

  • 1 roots pump, 2.000 m³/h
  • Measuring tube for measuring the vacuum
  • 2 single stage air cooled rotary vane pump with gas ballast, air cooled motor, 300 m³/h
  • Condenser, water-cooled, with solenoid valve for condense, inspection glass and level limiter
  • spring buffer
  • oil filter
  • sturdy platform for the whole vacuum station
  • All necessary valves, pipes and control devices.
  • Connecting pipe with compensator and flanges, connecting vacuum pumping station and oven

Cold water aggregate

In order to prevent the vacuum pumps for damage from hot air of oven, a cold water aggregate will be delivered in order to supply cold water to the condenser of vacuum pumps.

ambient temperature: max. 50° C
including, buffer tank and circulating pump with motor.

Control Cabinet

The control system of the plant consists of the electrical control cabinet with all required contactors, switches, relays and fuse protections. The process control is done automatically by means of a freely programmable PLC system. The plant comes with a PLC and a 17” HMI” for visualisation. There are some programs pre-installed. All process parameter can be adjusted via this system. In automatic operation the pro-cess with all its steps like heating, pressure reduction and fine vacuum are per-formed automatically after input of transformer data via HMI.

The construction of the control cabinet is according to the relevant recommendations of VDE, DIN and VBG. The chamber door will be operated by a separate control panel.

In addition it is intended that the process runs automatically after applying „Process Start“, but also a semi-automatic operation shall be possible by selecting the individual parts of the process as heating phase, stop phase, drying phase and fine drying.

A manual process control is intended too, with which, however, all safety interlocks will be active.

HERING offers the right equipment for every application, in order to ensure an optimal price-performance ratio. There are generally two types of systems depending on the process used:

100 MVA: Hot-Air Drying Plant Easy setup

100 MVA Vapor-Phase Drying Plant Reduced process duration

In any case, HERING will help you to choose the right process for your specific application.

The Hot-Air Drying Plant and the VaporPhase Drying Plant are generally based on the same principle. Reducing the pressure leads to a lower boiling point, which causes the dissolved water in the transformer’s active part to vaporize. Generally there are three steps to the process: the heating-up phase, the evacuation of the autoclave and cooling.

The two methods only differ in the heating up phase (hot air and vapor-phase). Due to different magnitudes of heat transfer, the vapor-phase drying process allows for faster drying, whereas the hot-air process is easier to implement.

Work Operation

The complete drying plants are divided in sub modules. Each module, e.g. heating station or kerosene station, is completely piped, wired and pre-tested in our workshop.

This concept convinces with a fast, easy and safe installation of the plant. Additionally, the customers have the opportunity to set up the complete plant by themselves.

The complete drying plants are divided in sub modules. Each module, e.g. heating station or kerosene station, is completely piped, wired and pre-tested in our workshop.

This concept convinces with a fast, easy and safe installation of the plant. Additionally, the customers have the opportunity to set up the complete plant by themselves.

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