SILICA GEL AIR BREATHERS
FOR OIL FILLED TRANSFORMERS
General specifications
Humidity and impurities reduce the dielectric rigidity of the transformer insulating oil and contribute towards the forming
process of smudges thus impairing the correct operation of the transformer itself.
The intake air of transformers should therefore be filtered and dried that is dehumidified by means of an equipment
specially designed for the purpose and called Silica Gel Air Breathers.
Characteristics of Silica Gel
The above mentioned chemical agent for this equipment
is practically chemically pure (99,70% SiO2) silica gel.
The quantity of water vapour adsorbed by the above gel
rests on various factors among which the most important
one are: ambient air temperature and the relative
humidity of the former. At 100% relative humidity at the
temperature of 25°C (77°F) the gel adsorbs a water
vapour quantity up to 40% of its own weight, and above
these parameters the silica gel possesses no further
adsorption possibilities. The saturation thus reached is
evidenced by the colour change taking place in the gel
during the adsorption process. From the original blue
when the gel is dry, it turns pink when it is saturated.
When saturated silica gel may be reactivated by
submitting it to a drying at 150-200°C until blue colour
is reached.
Description of the Air Breather
This equipment consists of a hollow, medium thick plate
transparent cylinder which contains the silica gel, of a
stainless steel housing, flanged at its top and bottom ends
with anticorrodal blank flanges provided with
appropriate, threaded openings and connected among
them by means of screw bolts. The bottom flange is
fitted with a removable tank which is filled, when ready
for operation, with transformer oil up to about half the
height of the oil level check glass. In this tank there is a
hollow aluminium cylinder the bottom end of which in
the oil of the tank is immersed, whilst at its top end
protrudes into the gel cylinder and is provided with a
horizontal ring of holes.The compound oil tank and
hollow aluminium cylinder constitute a siphon, that is a
hydraulic trap which prevents the getting into contact of
the gel with the ambient air, as long as the transformer
operates at constant temperature, whilst, when suction
takes place, air is admitted under filtering action into the
transformer owing to the pressure difference prevailing
under such circumstances. Under inverse operating
conditions, the excess air is exhausted by the same way
bubbling through the oil. The intake air opening is
located at the bottom of the equipment, thus avoiding all
possibilities of rain water entering it.
There are several sizes of this equipment, and in those
containing a gel quantity ranging from 2 to 10 Kg, the air
intake opening is moreover fitted with a filter cartridge
which prevents the entering into the equipment of
whatsoever material. The threadedbore in the top flange
of the equipment serves for the connection with the
conservator oil suction pipe.
All external parts of the equipment are stove enamel
finished, except the stainless steel part of the housing.
Construction and operation
The air breathers consists of a hollow transparent
cylinder which contains the silicagel, of a steel housing
flanged and its top and bottom ends with light metal
blank flanges.The bottom flange is fitted with a
removable tank which is filled, when ready for operation,
with transformer oil up to half the height of the oil level
windows.In this tank there is a hollow cylinder the
bottom end of which in the oil of the tank is
immersed.The compound constitute an oil seal which
prevent contact between the atmospheric air and the gel
charge when no breaking is taking place, whilst, when
suction takes place, air is admitted under filtering action
into the transformer owing to the pressure difference
prevailing under such circumstances. The saturation of
silicagel is evidenced by the colour change taking place
in the gel during the adsorption process. From the
original blue when the gel is dry, it turns pink when it is
saturated.
Setting to work - Operating instructions
• Remove the sealing tape closing the air passage holes.
• Fill the gel container with silicagel.
• Screw the air breather to the pipe going from the
conservator.
• Remove the oil tank unscrewing the nuts at the bottom
of the breather.
• Place oil in the oil tank up to half the height of the oil
level windows.
• Replace the oil tank.
Maintenance: reloading and reactivaction of Silica Gel
When the pink colour of the indicator gel reached half-way up the container, the saturated charge should be replaced
operating as follows:
• remove the oil tank of the air breather;
• the saturated silicagel may be reactivated by uniformly
• unscrew the air breather and remove it;
distributing it on a thin sheet metal so that it is about 1"
• replace the saturated silicagel with the fully active one
(25mm.) thick, and then placing the sheet with silicagel
(all blue);
in a ventilated oven at a temperature of about 150°C,
• put the breather back into operation;
until the silicagel become blue.
• replace the oil tank;
Oil level check
Periodically check the oil level through the oil level windows. If the oil is dirty, replace it.
SILICAGEL AIR BREATHERS - TYPES
TYPE GEL FILL TRANSFORMER
kos.
OIL
H
D.
mm.
mm.
F
CONTAINER
CAPACITY
Approx daily
Total air volume
thermal breathing breathed in before
dm3
volume (m3)
reactivation (m3)
TV 75
0,17
ks. 700
155
82
1/2”- 3/8”
0,240 dm3
0,006
2,6
E0
0,20
ks. 800
160
100
1/2” F
0,265 dm3
0,007
3,1
E1
0,35
ks. 1500
210
100
1/2” F
0,465 dm3
0,012
5,4
E2
0,50
ks. 2500
180
140
1” F
0,800 dm3
0,018
7,8
E3
1,20
ks. 6000
270
140
1”F
1,600 dm3
0,036
15,6
E4
2,50
ks. 13000
350
190
1 1/2” F
3,200 dm3
0,079
29
E5
3,40
ks. 20000
440
190
1 1/2” F
4,500 dm3
0,127
46,6
E6
5,00
ks. 30000
410
240
1 1/2” F
6,750 dm3
0,205
78
E7
7,00
ks. 50000
510
240
1 1/2” F
9,400 dm3
0,283
103
BREATHER TV 75
POS
1
2
3
4
5
DESCRIPTION
cover
air hole
transparent gel container
oil wetted cylinder
removable transparent
pocket
BREATHERS E.0 – E.1
POS
1
2
3
4
5
6
7
8
9
DESCRIPTION
fixing hole
gel container
inspectioning windows
stainless steel housing
data plate
drain holes
oil window / air intake
oil tank
drain hole
BREATHERS E.2 ….E.7
POS
1
2
3
4
5
6
7
8
9
10
11
12
DESCRIPTION
fixing hole
n° 3 nuts
gaskets
gel container
n° 3 stainless steel tie rods
n° 3 inspectioning window
stainless steel housing
date plate
drain holes
oil tank
oil window
air intake