The Oil forced Air forced heat exchangers manufactured by CONVETT Oil Forced srl are designed for the cooling of the power trasformers.
The heat exchanger is divided in five components:
- cooling element exchange area
- external carpentry
- air fan section
- oil pump section
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.
The front side of the 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.
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.
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.
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
The heat exchanger Convett 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.
Please find all the technical details in the below links: