Magnetic Oil Level Gauges for electrical Transformers - TERMAN

Magnetic Oil Level Gauges
for electrical Transformers
Description and general specifications
Operating instructions and maintenance
Finished product quality control tests
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Description and general specifications.
The magnetic oil level gauges serve the purpose of visually indicating the oil level in a tank or in a
conservator of oil filled transformers.
This instrument is composed of a disc indicator (or a red pointer) behind a dial frame and a float linked to
said indicator by means of a magnetic field of force.
The indicator disc is for one half enamelled white and, for the other half, red. Alternatively the colour
proportion visible through the dial glass indicates the respective level position, whilst the dial face is marked
at minimum and maximum oil level and at level corresponding to 20°C and 85°C (on demand other markings
are available).
The oil level indicator's float follows the oil level fluctuations thus causing a permanent magnet to be shifted
in turn.
This last is connected, by means of a magnetic field of force, to another magnet located into the external part
of the oil level indicator casing. The rotation of the internal magnet will cause, on its turn, the rotation of the
external magnet which is integrally fitted to the disc indicator / red pointer. The magnetic joint consents to the
two-colour disc / red pointer to be not immersed in the oil but separated from it by an oil tight partition which
is cast integrally to the instrument's body.
When the conservator oil level is at its minimum there is visible within the dial only the red portion of the
indicator disc, whilst an oil level increase will progressively bring into prominence the white portion of the
indicator disc.
The gauge may be provided with one, two or four microswitches for signalling of minimum and/or and
maximum oil level.
Casing : weather proof light metal alloy, stove
enamel finished, suitable for outdoor mounting
Protection degree : IP 54.
Microswitches making & breaking capacity :
• 3A 125/250V AC (resistive)
• 0,5A 125V DC for inductive load L/R= 40ms
• 0,25A 250V for inductive load L/R= 40ms
Insulation test : 2000V 50Hz between terminals
and earth for a 60 sec. time.
Working temperature : all the magnetic oil level
gauge are suitable for working with:
oil temperature between -25°C / + 120°C
ambient temperature between -25°C /+ 60°C
Float movement : this may be in the radial
direction (type “B”) or in the axial direction (type
“A”)
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MAGNETIC OIL LEVEL GAUGE L80
MAGNETIC OIL LEVEL GAUGE L100
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MAGNETIC OIL LEVEL GAUGES type LA140 / 220 / 340
Type L140
30°
Type L 220
L 340
S
22°30'
76
24
53
N.HOLES Ø D2
+85
MAX
OIL LEVEL
O-RING
120°
60
Ø D1
Ø D
CENTRE OF
CONSERVATOR
+20
-20
MIN
LIVELLO OLIO
L
DIAMETER OF
CONSERVATOR
Ø DC
58
VARIABLE LENGHT
Ø 58
PG 16
TYPE ØD s ØD1 O-ring Ø d2 L N. holes Weight R standard
LA140 140 24 125 OR 186(6362) 7 245 6 1,9 kg. max 370mm.
LA220 220 24 190 OR 221 11,5 325 8 2,9 kg. max 550mm.
LA340 340 24 305 OR 248(8100) 18 445 8 6 kg. max 710mm.
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120°
120°
MAGNETIC OIL LEVEL GAUGES type LB 140 / 220 / 340
Type L140
30°
Type L 220
L 340
22°30'
90
24
53
Type L140
N.HOLES Ø D2
30°
Type L 220
L 340
+85
MAX
OIL LEVEL
22°30'
O-RING
90
24
53
N.HOLES Ø D2
60
Ø D1
Ø D
DIAMETER OF
CONSERVATOR
DIAMETER OF
CONSERVATOR
Ø DC
Ø DC
+20
-20
+85
+20
-20
MAX
MIN
MIN
LIVELLO OLIO
OIL LEVEL
LIVELLO OLIO
VARIABLE LENGHT
58
VARIABLE LENGHT
58
Ø 58
O-RING
60
Ø D1
PG 16
Ø D
L
L
Type ØD s ØD1 O-ring Ø d2 L N. holes WEIGHT R standard
LB140 140 24 125 OR 186(6362) 7 245 6 2,3 kg. max 370mm.
LB220 220 24 190 OR 221 11,5 325 8 3,3 kg. max PG 550mm.
16
LB340 340 24 305 OR 248(8100) 18 445 8 6,3 kg. max 710mm.
Type ØD s ØD1 O-ring Ø d2 L N. holes WEIGHT R standard
LB140 140 24 125 OR 186(6362) 7 245 6 2,3 kg. max 370mm.
LB220 220 24 190 OR 221 11,5 325 8 3,3 kg. max 550mm.
LB340 340 24 305 OR 248(8100) 18 445 8 6,3 kg. max 710mm.
Ø 58
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Operating instructions and maintenance.
OIL LEVEL INDICATORS type LA - radial float
Must be fitted offset with respect to the horizontal axis of the conservator ( distance "S" in the figure ) in
order to have an exact indication of the minimum and maximum oil level.
To calculate S use the formula :
S=(0,5DC- 40) x 0,577 DC= conservator diameter dimensions =mm.
The length of the float stem = R can be calculateted by using the formula :
R=(0,5DC -10) x 1,15 DC=conservator diameter dimensions =mm.
OIL LEVEL INDICATORS type LB - axial float
Must be mounted exactly in the centre of the conservator and the length of the float stem = R can be
calculateted by using the formula :
R=(0,5DC -10) x 1,15 DC=conservator diameter dimensions =mm.
Maintenance :
On regular basis check the functionality of the device by manually rotating the indicator disc thus verifying
the correct commutation of the contacts. The manual rotation must be made very slowly to avoid
disconnection of the magnetic field !
Being the transparent made of polycarbonate, when cleaning use a soft cloth and soapy water.
Finished product quality control tests.
Hydraulic test for tightness for the body : the aluminium alloy casing is filled with oil at the temperature of
90°C and at the pressure of 300 kpa.
After 8 hours no leakages must be observed.
The same test is carried out for float.
Dimensional check.
Hydraulic test for tightness of the finished gauge : the test is carried out by mounting the oil level gauge
on a tank filled with oil at the temperature of 90°C and at the pressure of 200 kpa. Said test lasts 4 hours.
During this period no oil leakage is admitted.
Manual and hydraulic inspection of the electric contacts actuation : this test is carried out both on
minimum and maximum levels circuits.
It’s performed by means of visual indicators mounted on a panel-board.
Check of instrument mechanical protection degree : IP 55.
Isolation test : carried out by means of a microprocessor controlled testing unit.
I EDITION AUGUST 2006
Terman '90 S.r.l., Via Ghisalba, 13-20/21, 20021 Bollate (MI) – Italy. Tel: +39 02 38 30 37 12, Fax: +39 02 38 30 37 19,
E-Mail info@terman.com, www.terman.com
C.F./P. IVA IT 09970270154 – C.C.I.A.A. 1332904 – Trib. Milano Reg. Soc. 302729 – Cap. Soc. € 119.000
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