To process the windings of transformers, electrical parts and apparatuses, a special electrically insulating varnish is used. Such funds can be of three types:
- Impregnating agents that are used to improve electrical conductivity. They fill with themselves all the free space between the wires, connecting them together.
- Coverslips that are used as additional protection for already treated surfaces.
- Adhesive. Connect several electrical insulating elements.
One of the impregnating agents for electrical insulation is the varnish ML-92.
Characteristics and basic properties
This tool due to its electrical insulating properties withstands the effects of current, electric arc, electrical voltage. The varnish has good insulating characteristics, which do not change in any way when exposed to moisture or steam.
Features of the film formed on the surface after using varnish:
- Oil resistant.
- It has good electrical strength at various temperatures.
- Heat resistant
- Thermoplastic (can withstand more than two days at a temperature of 148-152 degrees).
Under normal conditions (temperature 20 degrees) conditional viscosity 25-50 s. The hardness of the film under the same conditions is more than 0.4 srvc.
After drying, the ML-92 varnish forms a protective coating on the surface of the winding, which is resistant to various weather conditions. The product can withstand temperatures up to plus 130 degrees. According to GOST-8865, this tool belongs to the class "B" for heat resistance.
Apply varnish outdoors in the open air or under a canopy. In enclosed spaces, where the conditions are similar to the street ones in temperature and humidity, an influx of fresh air is provided, exhaust ventilation works, it is also permissible to use ML-92 varnish.
The price of the product is 100-600 rubles per 1 kilogram. The cost varies depending on the manufacturer, class, packaging.
Insulating varnish is a homogeneous liquid without mechanical impurities, consisting of glyptal varnish and melamine-formaldehyde resins. Dilute the varnish with organic solvents (toluene, xylene or a mixture thereof with white spirit). The content of non-volatiles is 50-55%.
The surface varnished becomes homogeneous, glossy, smooth, brown (the shade can vary from light to dark).
The consumption of funds is estimated as 40-50 g / m 2 when applying one layer with a thickness of 20-30 microns.
The electric strength of the product depends on the temperature. Under normal conditions (18-22 degrees with a plus sign), this value is 70 MW / m. As the temperature rises to 130 degrees, the electric strength decreases to 40 MV / m. When the varnish is in a humid environment for 24 hours at a temperature of 20 degrees, the electric strength will be 30 MV / m.
Application
It is necessary to apply the insulation composition on a dry, dust-free surface.
Before use, the varnish is thoroughly mixed. It is used at air temperatures from minus 60 to plus 130 degrees.
Varnish ML-92 is applied by two methods:
The varnish layer should be uniform, without drips.
It is recommended to apply in 1-2 layers. Between application stand for 15-20 minutes (at 20 degrees). The same interval is maintained between the last layer and hot drying. Dry for one hour at 105-110 degrees. With multi-layer application, the varnish ML-92 is dried at a temperature of 120 degrees for about 16 hours.
Packing and storage
Insulating varnish ML-92 is available in industrial containers weighing 15 (flask), 25 (drum), 57 kg (barrel).
It is allowed to store the product in tightly closed packaging in places where moisture does not penetrate, direct sunlight and there is no exposure to high temperatures. Subject to the necessary conditions, the shelf life is one year from the date of production.
Safety precautions
Varnish ML-92 releases into the air the volatile chemicals present in its composition. Therefore, when used indoors, good ventilation should be provided. Upon completion of work, the room must be thoroughly ventilated.
When working with an electrical insulating agent, personal protective equipment (rubber gloves) must be used.
Do not use near an open flame. Observe fire safety regulations.