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Hedrich vacuum systems
Drying technology for oil/paper insulated products
Presented by Gerhard K. Mais
Hedrich Group
Member of the Board
Sales & Engineering
www.hedrich.comThe Products…
Drying of distribution and power transformers
Drying of X-ray transformers
www.hedrich.comThe Products.,.
Drying of high voltage bushings
and instrument transformers
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Drying of :
Motors and stators
High voltage capacitors
High ang highest voltage cable
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1. Conventional drying process with hot air/vacuum
2. Advanced drying according to the vapour-phase process
3. Drying with low-frequency heating
4. Drying of capacitors/cables/motors/stators
5. Summary
Content of presentation
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Conventional heating process for transformer coils and active parts
conventional drying process
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Conventional heating process for transformer coils and active parts
conventional drying process
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Conventional heating process for transformer coils and active parts
conventional drying process
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Conventional heating process for transformer coils and active parts
conventional drying process
www.hedrich.comconventional drying process
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www.hedrich.comconventional drying process
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Drying time of transformerwindings by hot air/vacuumcirculation processversus voltage and power
conventional drying process
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Distribution transformer drying and filling plant
conventional drying process
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Hot air circulation vacuumdrying equipment
conventional drying process
www.hedrich.comConventional drying process
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1. Conventional drying process with hot air/vacuum
2. Advanced drying according to thevapour-phase process
3. Drying with low-frequency heating
4. Drying of capacitors/cables/motors/stators
5. Summary
Content of presentation
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Historic development of the
vapour phase drying equipment
Vapour phase drying process
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Generation V, Expansion Evaporation System2003
Generation IV b, Thin film evaporator system in compact design2004
Generation IV a, Thin film evaporator system in modular design1995
Generation II, Circulation evaporator
Generation III, Cascade evaporator
1973
1992
Generation I, Immersion-tube evaporator1970
Generation 0, “Westinghouse” System< 1950
Development over 60 years…
Vapour phase drying process
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Generation 0
Vapour phase drying process
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Generation I
1. storage vessel for solvent
2. Immersion-tube evaporator
3. main condenser
4. water/solvent separating vessel
5. autoclave
6. condensate collection vessel
7. leakage air vacuum pump
8. solvent feeder pump
9. filter
10. heat exchanger
11. vacuum pump unit
Vapour phase drying process
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Generation I
Immersion Tube Evaporator
This type is designed in such way that a sufficient quantity of kerosene maintains the relative oil concentration in evaporator 2 at low level (even with oil dilution). Thus, a heating process is completed in most cases, without interruption during intermediate distillation. Compared to other evaporator systems, the energy requirement is higher as well as the kerosene quantity.
Vapour phase drying process
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Generation II - Circulation evaporator
Vapour phase drying process
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Generation II
Circulation Evaporator
This evaporator type is the basic evaporator system and has so far been installed in older HEDRICH vapour-phase plants. It is suitable for installations where normal oil quantities are expected. Kerosinequantity in the evaporator is much less than in immersion tube evaporator.
Vapour phase drying process
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Generation III - Cascade evaporator
1. autoclave with cascade evaporator
2. condensation device
3. vacuum pump unit
4. storage vessel kerosene
5. feeder pump for kerosene
Vapour phase drying process
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Generation IV - Thin film evaporator
Vapour phase drying process
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Generation IV - Thin film evaporatorThis type of evaporator represents the technology which is presently used in all pieces of standard Hedrich vapour phase equipment.
An essential advantage of this evaporator is that it is arranged outside, but very close to the vacuum drying tank. Thus, the useful area provided in the drying tank is not limited. An explosion proof evaporator room does not need to be provided in the workshop as for the other evaporator systems described before.
Vapour phase drying process
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• No explosion-proof evaporator room necessary
• Exact temperature regulation without delays,
• Less energy consumption due to considerably reduced quantities ofkerosene
• Evaporator outside of drying tank. Thus, no limitation of useful areain the drying tank
• After the feeder pump is switched off, the evaporator is immediately freefrom kerosene. This means a considerable increase of safety
• Continuous separation of transformer oil during pressure reducing phasesand during fine drying, independent of the drying tank
• Excellent separation of the oil and almost complete recovery of thekerosene.
Advantages of thin-film evaporator design
Vapour phase drying process
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Generation IV a
Wall of the autoclave is used for the assembly of the equipment
Thin film evaporator attached directly to the walls of the autoclave.
Vapour phase drying process
Thin film evaporator system
in modular design
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Generation IV b
Recently more and more customers ask forTurn Key – delivery making it necessary to develop a compact design.
Advantages:
• Standardization of the design.
• Assembled and tested in Hedrich work shop.
• reduction of assembly and commissioning time on site.
Disadvantages:
• Higher costs because of transport and the frame.
Thin film evaporator system in compact design
Vapour phase drying process
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Generation V
Mobile system for drying repair power transformers on site. First system tested in Germany in 2003.
Evaporation based on the expansion of pressure charged solvent via expansion valves.
Complete equipment size reduced to assemble it in “one” frame.
Stationary system developed as a “low cost – easy to install” system
First stationary system in operation in Turkey since 2007.
Expansion Evaporation System in compact design
Vapour phase drying process
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Generation V 1 autoclave2 transformer3 main condenser4 valve5 water/solvent
separating vessel6-7 valve8 Condenser9 cooling water 10 Vacuum pump11-12 valvesLS13 level sensor14 solvent pump15 filter16 heat exchanger17 heating device18 expansion valves19 feeder pump20-23 valves24 storage vessel
Expansion Evaporation System
Vapour phase drying process
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Expansion Evaporation System
Vapour phase drying process
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Expansion Evaporation System
Vapour phase drying process
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More details about the
Vapour phase process..
Vapour phase drying process
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Process sequence of vapour phase
Vapour phase drying process
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For the different heating processes, the following approximate typical
figures of heat transfer can be estimated:
Radiation - abt. 8 kJ/h m² K = 2,2 W / m² x K
Convection - abt. 80 kJ/h m² K = 22 W / m² x K
Oil Spray - abt. 600 kJ/h m² K = 167 W / m² x K
Vapour-Phase - abt. 4500 kJ/h m² K = 1250 W / m² x K
Vapour phase drying process
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max. limit
VP-process
conventional-process
Vapour phase drying process
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• 20° C higher drying temperatures are possible due to process under vacuum
• Optimum heat transfer, mainly due to droplet and film condensation
• Local overheating of insulation is avoided.
• the insulation is less stressed by approx. 15 %.
• Interval pressure reductions for more effective removal of water
• Optimally short drying times until residual moisture of 0.3 % is reached.
• 50 – 70 % reduction of drying times
• energy saving drying process
• no oil contamination of production area
• higher production capacity with the same floor space requirements
Advantages of the vapour phase process
Vapour phase drying process
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Vapour phase drying process
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The Hedrich vacuum pumping unitoffers the following advantages
• non-polluting because of kerosene recovery• robust stainless steel design• unlimited water vapour capacity• insensitive to vapours• almost maintenance-free.• designed to handle acid that is performed at the pump exit• The final vacuum of this vacuum pumping unit is in the range
of 10-3 mbar
Vapour phase drying process
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• in-line measuring system• determination of exact drying end• time and cost saving automatic method• continuous measuring of partial water vapour pressure
1
2
3
4
PROBE CONSTRUCTION
Three Major Components
1. Thin film aluminum oxide sensor
2. Sensor’s probe mount
3. Protective shield
4.Thermistor
Automatic determination of drying end
Vapour phase drying process
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modern controlcabinet with :
- PLC- PC- automatic datamanagement
- remote service viainternet
Vapour phase drying process
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Vapour Phase equipment pre assembled in Hedrich work shop before insulation
evaporator (item 2.1)
kerosene collecting vessel(item 6.1)
vacuum pumping unit(assembly 4)
kerosene pumps(item 6.7, 6.7.1, 1.7)
kerosene/water separating vessel(item 3.8)
kerosene vapour to the autoclave
kerosene/water vapour from the autoclave
secondary heating circuit evaporator(item 2.9, 2.10)
main condenser (item 3.1)
inlet port for evacuating the autoclave
condensate collecting vessel (item 4.19)
secondary heating circuit autoclave(item 5.11-5.13)
Vapour phase drying process
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Essential advantages in summary of the Hedrich vapour phase systems• Thinfilm-evaporator with minimum amount of kerosene – safety !
• Patented condensation device with minimum energy needed
• No overheat-radiation in the autoclave (evaporator outside)
• Best oil/kerosene separation available worldwide (during pressurereduction and fine-vacuum phase) - best quality - time saving
• Most robust design with liquid ring pumps(kerosene as operating liquid)
• Liquid ring pumps in stainless steel design – acid resistant
Vapour phase drying process
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• Energy saving design
• No cooling water re-cooling necessary forpumping unit - energy saving
• Minimum maintenance designed equipment – worldwide
• Most modern plant control
• Most accurate online specific waterrrate - measurementsaving of actual process time
• Hedrich is the only supplier in the world that developeda mobil/staionary vapor-phase plant concept in compactdesign
Vapour phase drying process
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Hedrich`s strength for the customer
• more than 40 years experience in oil/paper insulation business
• strong technical background
• innovative in the most important field „vapour phase drying“
• exceptional growth of the company with more than250 employees in the meantime
• manufacturing locations in germany, switzerland and china
• service from the above mentioned locations
• further extension on all 3 manufacturing locations alreadystarted to be finished within the next 10 month
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Isostatic Pressing Equipment
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Hydraulic Equipment for cold pressing
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Hydraulic Equipment for hot pressing, 200 bars, 10 connections
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Pressing of 9 Windingssimultaneously
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hydraulic connections in drying tank
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hydraulic pressing tools
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Thank you for your attention
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