All power transformers have a conservator part, which holds the insulating oil for the transformer. The purpose of the insulation oil is to safeguard all parts of the transformer from current surges. The oil runs through the length and breadth of the transformer.
When the current through the transformer increases, the heat dissipated is more. The increased heat gets into the insulating oil, reducing its density and increasing the volume. Thus the air from the insulating oil gets trapped in the conservator top section. When the temperature decreases, the volume is increased, and the trapped air flows back into the insulation oil. The presence of moisture in the air causes the oil to be impure, and the impure insulation oil may damage the insulation parts, which will result in dangerous current leaks from the transformer.
Silica gel breathers are employed in transformers to avoid such situations. The crystals act as an adsorbent and adsorb the moisture content from the oil into its pores.
Silica gel breather Design
A silica gel breather design is simple and easy to install. The arrangement is placed inside the transformer conservator and includes a pot or tube filled with fresh silica gel. This is placed above the oil level, to remove maximum moisture from the air. By protecting the insulating oil, silica gel assures insulation to the entire transformer parts.
The working principle behind Silica gel Breather
Silica gel is the amorphous silicon dioxide in its crystal form. The porous silica gel, in beaded form, has a high adsorption rate and traps water or moisture content in its surroundings. It is thus used as a desiccant or drying agent in many scenarios. By adsorbing the moisture content from its surroundings, these desiccant crystals help to keep the medium dry. Few of its routine applications include the silica gel sachets in electronics packets, shoe bags, medicine boxes, etc.
Here, as the silica gel bed acts as a drying agent for the transformer insulation oil, it traps the moisture from the air released as a result of the transformer breathing. Silica gel blue and orange are the best choices for this purpose.
Regeneration of silica gel beads & crystals
Moisture from the insulation oil can make the crystal bed saturated. But one most valuable advantage of silica gel is that it is reversible. The crystal bed can be processed to remove water molecules and thus reused multiple times.
Silica gel adsorb moisture from their medium and nearby substances by trapping the water molecules in their pores. Studies show that about thirty percent of its weight of water vapor is adsorbed by silica gel. Thus it is considered one of the best desiccants in the market.
To reactivate, silica gel is heated to 120 degrees Celsius for a minimum of 1-2 hours. Silica gel desiccants used in power transformers might be highly saturated and may require thorough reactivation. It is thus advised to process the desiccant bed for 4-6 hours at a temperature between 105-110 degrees Celsius. This process will reactivate the entire silica gel bed by reducing moisture to below 2% by weight.
In their pure form, silica gel beads & crystals are transparent and slightly whitish. But the desiccants are processed by impregnation to impart color-changing properties. Thus there are majorly two types of silica gel desiccants, indicating and non-indicating. The indicating silica gel will turn color depending upon the percent of moisture adsorbed. Color-changing silica gel make it easier to detect the saturation percentage and decide upon the necessity of dehydration.
Features of silica gel crystals
Many features of silica gel account for this application. They are:
- High adsorption capacity - up to 40% of its weight
- High efficiency
- Can be purged to remove water, once saturated
- Can be reused
- Easily available
- Safe to use
- Leaves no chemical residue
- Stable and reliable performance
- Inert property - will not corrode or disrupt the medium
- High shelf life
Sorbead India is one of the leading producers of silica gel beads & crystals. The indicating desiccant beads & crystals are widely used in breather transformers. We supply customized quantities of the silica gel, all across India. The affordable rates and quality products make us the most trusted store for silica gel beads & crystals, over the last years. With various levels of quality and security checks, the desiccants are made to perfectly suit every application as the breather transformers.