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PRODUCTS |
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KVPD-series Vapor Phase Drying Equipment |
| Vapor Phase Drying Equipment (VPD) is mainly suitable for drying active parts of supervoltage and high-capacity transformers up to 110kV or above, instrument transformer and etc. |
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1、Working principle:
The basic principle of VPD equipment: kerosene is heated and evaporated under vacuum state to become high-temp. kerosene vapor that will be condensed when meeting the lower temperature work pieces so as to release latent heat (about 306.6kJ/kg) to heat the active parts. After heat exchanging the condensed kerosene is collected and returned to evaporator again to be heated and evaporated through kerosene transportation system, so the temperature of drying work pieces is rising continuously. At the same time, the moisture in work pieces are evaporated into vapor continuously and be pumped out of autoclave to achieve completely drying.
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2、Process flow of VPD
①Preparation phase:
Put transformers into autoclave and evacuate the autoclave up to 700Pa. Meanwhile autoclave is heated, insulated and kerosene is preheated by evaporator to make outlet temperature of kerosene vapor rise from 98℃ to 130℃ gradually, kerosene changes from liquid into vapor and begins to diffuse in the autoclave and exchange heat with work pieces.
②Heating phase:
Vacuum system is operated by process pump. The vacuum degree of autoclave and condensation collecting tank are maintained within the vacuum that process required. Evaporated kerosene vapor exchanges heat with transformers and condensed kerosene vapor is drained out from the bottom of autoclave, finally returns to evaporator to form a cycle. With the continuous rising of autoclave temperature, the pressure of autoclave rises gradually due to kerosene vapor, water vapor of insulation material evaporated and leakage rate. At this moment the above mixed vapor is pumped into condensation recovery system to be condensed and separated through process pump. Condensed kerosene liquid is delivered to evaporator again to be heated and evaporated. The above process will continue until the temperature of work pieces reaches that of process required and then be ready to enter pressure reduction phase.
③Pressure reduction phase (or low vacuum phase):
It is stopped to delivery kerosene to autoclave. The kerosene and mixed vapor are pumped out of autoclave and the residual kerosene on insulation material is re-evaporated to facilitate condensation recovery. Intermediate pressure reduction phase and heating phase can alternate for several times in order to achieve the best drying effect.
④High vacuum phase:
The autoclave is evacuated by main vacuum system and the final pressure should reach 10Pa below. 95% moisture of insulation material has already been drained out before high vacuum phase. So it would not take a long time to reach high vacuum phase. The end of drying process can be determined when the work pieces reach the set temperature and the water extraction rate of insulation material is less than 10g/hour per ton. |
3、Process features of VPD:
●Take the kerosene as the heating medium to achieve heating under vacuum. Due to saturation pressure of kerosene is far less than that of water but higher than transformer oil, moisture can be smoothly discharged out during heating phase. After heating, kerosene is evaporated quickly without effecting diffusion coefficient of water at high vacuum phase. Use the condensed heat of kerosene vapor to heat work pieces, the lower temperature the more condensation, that is, the more released heat. So the temperature of work pieces is uniformity.
●Transformers are heated from 110℃ to 130℃ under vacuum, without worrying about aging of insulation material. Although the heating temperature is increased more than 10 ℃, the partial pressure of water vapor will be increased to 9.8×104Pa, it is very helpful for moisture evaporation. In addition to convection heat transfer mode, insulation material is heated by condensation heat transfer. And condensed kerosene exchanges heat on the surface of insulation material. This kind of heat exchange efficiency is higher than any of others, so the hating speed is very fast. Due to work pieces are under vacuum during kerosene vapor drying process, water extraction process runs through the whole drying cycle. At the same time, diffusion coefficient of moisture inside of insulation material is increased due to the rising temperature of work pieces, so as to shorten the drying cycle.
●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. Uniform temperature is very important for drying.
●Taking condensed kerosene on the transformers as a good cleanser, the dust can be washed out. It is the special feature of VPD plant and this is the main reason why VPD plant is most suitable for repairing transformer handling. After processed, the surface of work pieces is clean, stainless. |
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Technical features of VPD:
1、Introducing and absorbing the latest technology of MICAFIL and combining with more than 20 years’ design and manufacture experiences in vacuum equipments, our equipments are characterized by stable control system, reliable operation, high efficiency, reasonable layout, modular design, and convenient maintenance with our independent research, development and innovation.
2、It is equipped with build-in cascade evaporator, which can carry out distillation between two heating phases, meanwhile which also can heat the work pieces during distillation. It is characterized by energy saving and safety.
3、Individual heat recovery system installed at outside of autoclave can maximize to recover heat energy and save energy.
4、Water extraction quantity of each intermediate pressure reduction phase and total water extraction amount can be recorded in time and displayed on computer screen. Water extraction curve of each intermediate pressure reduction phase and total water extraction amount curve can be drawn. And water extraction rate of each intermediate pressure reduction phase can be calculated automatically.
5、The condensation flow of mixed kerosene & water can be measured real timely so that the returning mixed kerosene & water can be controlled, rather than totally dependent on the control of autoclave’s pressure. In this way the control will be much more scientific and reasonable.
6、The end point can be measured automatically by computer. The process will be cut off automatically when the temperature of work pieces reaches 120℃±5℃, pressure of autoclave is up to ≤0.2mbar and water extraction rate is less than the set value.
7、We choose famous products both at home and aboard as accessories, and choose imported famous product as key elements. Work pieces are designed, manufactured and inspected according to standards and specification of vacuum industry, and relevant standards of national machinery manufacturing industry. They are of parts standardization and interchangeability.
8、The whole process can be fully controlled automatically, and even can be operated unattended. The computer can monitor the technics process of product and display technics parameter and curve of each phase. Various technics curve and reports can be printed timely and automatic technics data backup.
9、Control system interface is characterized by humanization. It can reflect the running status of equipment and process of products timely.
10、Visible & audible alarm can be done automatically. And usual troubleshooting methods can be provided. Malfunction point and time can be recorded timely.
11、Various parameters and the implementation state of program can be saved when power failure suddenly.
12、Technics parameters can be displayed and revised.
13、It has the function of distribution and restricting of user’s rights. The prior user can distribute and restrict the less prior user and make sure the system operation in order.
14、Our patented product can be used as drying end point measurement: drying end point detector with accuracy, high automation and reliable measurement for dew point. |
Specifications of VPD
Above specification is for reference only, autoclave size can be designed according to the requirement of customer. |
| Structure： |
1、Autoclave one set
2、Vacuum system one set
3、Condensation system one set
4、Kerosene evaporation and distillation system one set
5、Kerosene storage and transportation system one set
6、Heating system one set
7、Hydraulic system one set
8、Pneumatic system one set
9、Cooling water system one set
10、Control system one set
11、Explosion-proof ventilation system one set
12、Spare parts one set |
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| Applications: |
| AREVA T&D India Ltd, Baroda - 300KW |
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| AREVA T&D India Ltd, Baroda - 500KW |
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| Ningbo Transformer Manufacture Co., Ltd. - 300KW |
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| Xian Transformer Manufacture Co., Ltd. - 400KW |
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| ALSTOM South Africa - 300KW |
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| (Taiwan) Yung Heng Machinery & Electric Industry Co., Ltd - 250KW |
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| AREVA T&D India Ltd, Naini - 250KW |
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| AREVA Wuhan Transformer Plant - 300KW |
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| Guanggao H.V. Electric Apparatus Co., LTD - 300KW |
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The computer-controlled interface --- Schematic diagram
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The computer-controlled interface --- Processing curve
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