7 - The dehydrating breather

 The dehydrating breather is provided at the entrance of the conservator of oil immersed equipment such as Transformers and reactors.

The conservator governs the breathing action of the oil system on forming to the temperature change of the equipment, and the dehydrating breather removes the moisture and dust in the air inhaled and prevents the deterioration of the Transformer oil due to moisture absorption.

Construction and Operation

See Fig. (20) The dehydrating breather uses silica - gel as the desiccating

Agent and is provided with an oil pot at the bottom to filtrate the inhaled air.  The specifications of the dehydrating breather are shown in Table (1) and the operation of the component parts in Table (2).

 Fig. (20)  Dehydrating breather

1. Case

2. Peep window

3. Flange

4. Oil pot

5. Oil pot  holder 

6. Breathing pipe 


8. silica-gel


10. Oil (Transformer oil)

11. Wing nut

13. Suppression screw

14. Set screw 
15. Oil level line (Red


Table - 1



Weight of




Desiccating agent


4.5 kg

Material --- Silica-gel (Main component SiO2)

Shape, Size --- spherical, approx. 4 5

Mixed ratio --- white silica-gel  75%

                         blue silica-gel    25%


Table - 2






Removes moisture in the air inhaled by the Transformer Or reactor.

Blue silica


In addition to the removal of moisture, indicates the Extent of moisture absorption by discoloration.

(Dry condition) (Wet condition )

Blue ------ Light purple ----- Light pink

    Oil pot

Oil and filter

Removes moisture and dust in the air inhaled by: the Transformer or reactor. In addition, while it is not performing breathing action, it seals the desiccating agent from the outer air to prevent unnecessary moisture Absorption of the desiccating agent.




Absorbs dust and deteriorated matter in the oil pot, to Maintain the oil pot in a good operating condition.