CONVETT OIL - AIR COOLERS

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2 Cooling way the srl is a company founded in 1981 by Mrs. Margherita Carta Veller and it is a worldwide recognized as a manufacturer of cooling systems for power and distribution transformers. Our mission is the continuous improvement in all our strengths which are the innovation, the quality, the flexibility and the service, with a particular attention to the competitiveness. A short description of our milestones shows how we follow the mission since 1981: the company was founded first radiators automatic line second radiators automatic line start up of production of corrugated walls with the 2nd worldwide LAE complete machine certified as meeting the ISO requirements built a brand new plant of 3500 m with 400 m of offices second corrugated walls automatic lines water based painting process change from solvent base start up of production of OFAF systems and new company new painting equipment with a water base technology by immersion new LAE corrugated walls press and seam welder third radiators automatic line with Robot technology new LAE spot welding and strip welding machine new automatic line for welding the radiators elements new equipment for finned tubes for heat exchangers expansion of 500 m of building for OFAF-OFWF systems first prototype of OFWF coolers During the last two years srl restructure the company in a major way and invested in new equipments and automatic assembly lines (in all the three products) human resources (recruiting and training), safety and quality. We now offer the entire range of cooling systems from the corrugated walls, the radiators and the oil forced-air forced heat exchangers. These products are successfully exported to East and West Europe, North and South Africa, the far East and South America. R&D is also developing the Oil Forced Water Forced (OFWF systems ) heat exchangers to complete the cooling transformers product offer to our customers.

3 The Oil forced - Air forced heat exchangers manufactured by Oil Forced are designed for the cooling of the power trasformers. The heat exchanger is divided in five components: 1 - Cooling element exchange area 2 - External carpentry 3 - Air fan section 4 - Oil pump section 5 - Accessories COOLING ELEMENT EXCHANGE AREA The cooling element exchange area represents the cooling area of the exchangers and it is made by finned tubes in aluminium without turbolators. The tubes are connected at both ends with tube sheets. The tube sheets are made of steel (Fe 360) or of aluminium. In order to avoid any micro leakage and above all the protect the tube sheets from the corrosion we apply a special resin on the top of the external part of it. The cooling element exchange area is tested 100% at 5.5 bar, it is also equipped with oil headers for oil collecting and guiding to the transformers oil circuit. This oil headers has standard air vent and oil drain plugs, but any specific requirement can be satisfied. The oil headers are mounted to the cooling element with bolts and the oil tightness is guaranteed by a sealing gasket. This mechanical design allows an easier maintenance or cleaning of the cooling element if necessary. The entire cooling element goes through a cleaning process of 8 hours with a specific transformer oil forced system equipped with 20 microns filters. At request the cooling element can also be made of stainless steel or other special materials. The cooling element is over dimensioned by a minimum of 10% in order to allow the plugging of 1-2 tubes if requested for maintenance.

4 EXTERNAL CARPENTRY The external carpentry is the mechanical interface between the cooling element and the power transformer. It is made entirely in steel (Fe 360), and completely painted following the painting cycle requested. The flanges are DN100 PN10. If requested the carpentry can also be made of stainless steel, or can be hot dip galvanized. AIRFAN SECTION The front side of the Oil Forced cooler has between one to three axial fans, with air direction in both sides ( forced or induced draft type) following the customer request, and the fans have a variable number of blades made of steel, light alloy, or composite material (for low sound pressure devices). The motor are three-phase AC, and has different number of poles, depending on the customer needs.

5 OIL PUMP SECTION The electrical pump is necessary for the oil circulation inside the heat exchanger and the transformer. The loss reserved to the transformer circuit is approximately 1 meter of water column. Convett oil forced has decided to offer a reliable pump from a worldwide pump manufacturer leader to offer to our customer the best quality and technology available in the market. There are two different pump types that can be mounted to the heat echnagers: a) roto-dynamic pumps driven by a squirrel cage induction motor which is immersed in the insulating oil b) roto-dinamyc pumps with external motor, and a mechanical special construction to guarantee the oil function HEAT EXCHANGER The heat exchanger Oil Forced does not need special maintenance. For the air side is recommended for normal atmospheric condition, not particularly polluted, an yearly cleaning of the finned tubes, external side. This operation can be made with pressurized air (max 5 bar) and air direction parallel to the thin at a distance minimum of 100mm, without touching the thins. The oil side, internally, can be cleaned with metallic brushes, or can be cleaned with some special dedicated liquid. SPECIAL ACCESSORIES It is possible supply the cooler with special accessories in both the air and the oil side, such as manometer, thermometer, oil-air circulation sensor.

6 OIL - AIR COOLER 1 A C B E G H FLANGE DN100 VENT PLUG DIN F OIL IN I AIR FLOW D TERMINAL BOX OUTLET VALVE 1/2" G OIL OUT FLANGE DN100 measures shown in mm A B C D E F G H I 1-D 1-E OIL - AIR COOLER 2 B E G H FLANGE DN100 VENT PLUG DIN OIL IN I A C AIR FLOW D AIR FLOW TERMINAL BOX OUTLET VALVE 1/2" G FLANGE DN100 OIL OUT measures shown in mm 2-C 2-D 2-E 2-F 2-G A B C D E F G H I

7 C B E G H FLANGE DN100 VENT PLUG DIN OIL - AIR COOLER 3 I OIL IN AIR FLOW AIR FLOW D A AIR FLOW TERMINAL BOX OUTLET VALVE 1/2" G FLANGE DN100 OIL OUT measures shown in mm A B C D E F G H I 3-D 3-E 3-F 3-G

8 CHARACTERISTICS CHART 1-D 1-E 2-C 2-D 2-E 2-F 2-G 3-D 3-E 3-F 3-G POWER LOSS [kw] 75 OIL FLOW [l/min] 600 PUMP FAN WEIGHT [kg] OIL [kg] 0,9 kw = PRI09A 1,1 kw (1,5 HP) = VA11A ,9 kw = PRI09A 1,1 kw (1,5 HP) = VA11A ,1 kw = PRI11A 1,1 kw (1,5 HP) = VA11B ,1 kw = PRI11B 1,1 kw (1,5 HP) = VA11B ,1 kw = PRI11B 1,1 kw (1,5 HP) = VA11B ,5 kw = PRI15A 1,5 kw (2,0 HP) = VA15A ,5 kw = PRI15A 1,5 kw (2,0 HP) = VA15A ,5 kw = PRI15B 1,5 kw (2,0 HP) = VA15A STANDARD PARAMETERS In temperature oil: 90 C Ambient air temperature: 40 C; ,0 kw = PRI20A 1,5 kw (2,0 HP) = VA15A ,0 kw = PRI20A 1,5 kw (2,0 HP) = VA15A ,0 kw = PRI20A 1,5 kw (2,0 HP) = VA15A Fan with six poles motors 50 Hz; Trafo oil loss 1 m.c. H MOUNTING TYPES HEADER POSITION HEADER TYPE A A B C PIANO DI RIFERIMENTO A B C B AUXILIARES OIL CIRCULATION PUMP Two pump types per customer request Roto-dynamic pumps driven by a squirrel cage induction motor which is immersed in the insulating oil Roto-dinamyc pumps with external motor, and a mechanical special construction to guarantee the oil function Our standard is with power supply from 220V to 600V, frequency from 50Hz to 60Hz. For electrical characteristics please read the pumps manufacturer catalogue FANS Axial fans: our standard is with 6 poles motors (70 2m), with protection grid and the air is drawn through the cooling element, fan draw hot air ( forced draft type). But it is also possible to provide fans which supply cold air to the cooling element (induced draft type). OPTIONAL ACCESSORIES Tube sheet in aluminium Oil circulation sensor Air flow sensors Oil Inlet or outlet manometer Air Inlet or Outlet thermometer Top cover to protect from the rain in cooler position C SPECIALS Stainless Steel heat exchangers suitable for aggressive atmospheres Hot dip galvanized carpentry heat exchangers Low temperature (-50 C) resistant heat exchangers High temperature resistant heat exchangers Special design heat exchangers for functioning systems such as 2 + (1) or 1 + (2) Low sound level heat exchangers with poles fan motors and special blades construction Other special constructions, per customer demand, to be agreed with our technical department.

9 Measures, parameters and design, are for reference only and those have to be always verified with our technical office. srl and Oil Forced, might change some of them without notice. DTml [K] 60,0 50,0 40,0 30,0 20,0 10,0 0, POWER [kw] On our website you can download the enquiry form with an example of how to calculate wich cooler size to use. To decide the right dimension of the cooling unit read carefully and follow the steps below: a) Gather all relevant data such as : Tio, inlet oil temperature Tuo, outlet oil temperature Tia, inlet air temperature Q, power to dissipate b) Calculate the medium logarithmic temperature drop DTml with the following formula: Tua = Tia + (15/25) C (we suggest to use the 16C value) = Tia + 16C Dtml = (D1-D2)/ LN (D1/D2) where D1 = Tio - Tua and D2 = Tuo - Tia c) See in the chart above characteristics dissipation for a Convett Oil Forced Cooler and draw two lines in correspondence of the values of Dtml and of Q. d) The cross of this two values gives the right oil Forced cooler to use. It will be used the cooler identified by the line right below the crosspoint of Dtml and q. See example below. Example: a) Initial data: Tio, inlet oil temperature = 90C Tuo, outlet oil temperature = 83C Tia, inlet air temperature = 40C Q, power to dissipate = 315 KW CHARACTERISTICS DISSIPATION CURVES FOR A COOLER DTml [K] 1-D 1-E 2-C 2-D 2-E 2-F 2-G 3-D 3-E 3-F 3-G b) Outlet air temperature Tua = Tia + 16 = = 56 C c) Calculation of the medium logarithmic temperature drop DTml D1 = Tio Tua = = 34C D2 = Tuo Tia = = 43C Dtml = (D1-D2)/LN (D1/D2) = (34-43) / LN (34/43) = d) Cross the two lines of Dtml and q in the dissipation chart e) The nearest and lower line to the cross point between the two lines (the one for q = 315 Kw and the one for Dtml = 38,32 C is the black which correspond to the 3E Oil Forced cooler CHARACTERISTICS DISSIPATION CURVES FOR A COOLER 60,0 50,0 40,0 30,0 20,0 10,0 0, POWER [kw] 1-D 1-E 2-C 2-D 2-E 2-F 2-G 3-D 3-E 3-F 3-G

10 SOME PROJECTS REALIZED WITH OUR

11 NOTE Measures, parameters and design, are for reference only and those have to be always verified with our technical office. srl and Oil Forced, might change some of them without notice.

12 Oil Forced s.r.l Bressanvido (VI) Via S. Benedetto,14/Q - ITALY Ph: Fax: sales@convett.it