Description
Kerosene vapor-phase drying equipment (KVPD) is mainly suitable for drying transformer bodies in super-high voltage than 110kV and big capacity.
Working Principle
Under heating and vacuum condition, liquid kerosene will become vapor in high temperature. When vapor meets workpieces in less temperature, it will condense and release latent heat of condensation (about 306.6kJ/kg) which will heat workpieces. Condensed kerosene will be collected and re-transmitted to the evaporator to be heated again. In this way, under several cycles, temperature of workpiece increases continuously and moisture inside the workpieces evaporate to water vapor, to be taken out by vacuum and thus achieve complete drying on the workpieces.
Process Features
- Take kerosene as heating media which can carry heat and release heat by condensation. Kerosene condenses more acutely when there temperature is low. And so transformer body heating is more even.
- After kerosene vapor become liquid on the surface of workpiece, kerosene will also exchange heat with workpiece. And so the heat exchanging efficiency is higher than any other methods.
- Due to saturation pressure of kerosene is far less than that of water but higher than transformer oil, kerosene can be evaporated very quickly without effecting diffusion coefficient of water at high vacuum phase.
- Since heating is under vacuum without oxygen, when temperature raised from 110℃ to 130℃, insulation materials will not age; On the same time, the partial pressure of water vapor will be increased to 9.8×104Pa, which quickens moisture evaporating speed.
- Condensed kerosene is very easily infiltrated into the surface and internal of insulation material to accelerate its own thermal conductivity and to make deep temperature of insulation material is distributed uniformly (which is very important for drying)
- Condensed kerosene is also a very good cleaning solvent. It can wash out dust and dirt on the workpiece. This is very special feature only available on the KVPD drying. And so this kind of KVPD drying equipment is especially suitable for treating repairing transformers.
Technical features of VPD
- It is equipped with build-in cascade evaporator, which can carry out distillation between two heating phases.
- There is an individual heat recovery device outside of tank, saving energy
- Water extraction quantity in each phase and total extraction amount can be recorded on time and displayed on computer screen. Water extraction curve of each intermediate pressure reduction phase and total water extraction amount curve can be drawn instantaneously. And water extraction rate of each intermediate pressure reduction phase can be calculated automatically.
- The flow of kerosene in the mixture of kerosene & water can be measured instantaneously and so the opening rate of the main control valve can be controlled accurately, but not only rely on tank pressure control.
- The end point can be measured automatically by computer. The process will be cut off automatically when the temperature of workpieces reaches 120℃±5℃, and tank pressure is less than 0.2mbar and water extraction rate is less than the set value.
- The whole process can be fully controlled automatically, and even can be operated unattended. The computer can monitor the process of product and display process parameters and curve of each phase. Various process curve and reports can be printed timely and backup automatically.
- Visible & audible alarm can be done automatically. And usual troubleshooting methods can be provided. Malfunction point and time can be recorded timely.
- Various parameters and the implementation state of program can be saved when power failure suddenly.
- Process parameters can be displayed and revised.
Specifications
-Tank size: 7000 x 4500 x 4500mm~16000 x 6000 x 7000mm (as required)
- Heating power: 250kW~600kW (based on tank size)
- Max. working temperature: 135 ± 5℃
- Temperature controlling precision: ± 5℃
- Ultimate vacuity: ≤ 10MPa (non-load) |
