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CAUTION
During drying by the vapour phase process the cover of the diverter switch housing
and the bottom valve should be left open. The valve is opened with the special bottom
valve key, a long hexagonal rod. The maximum permitted temperature is 135
o
C
(275
o
F).
CAUTION
Use the special bottom valve key only (delivered with the on-load tap-changer) to
operate the bottom valve through the oil draining tube. The use of a stiffer tool may
damage the valve.
CAUTION
Do not operate the on-load tap-changer during the drying process or afterwards until
it is filled with oil, to avoid seizing.
Mounting of Gaskets
CAUTION
Sealing surfaces and gaskets must be clean and undamaged. Diametrically
opposed bolts in sealing joints must be tightened alternately several times, beginning
with a low tightening torque and finally with the recommended tightening torque as
described in section 1.8 Tightening Torque, in this guide.
During Oil Filling
WARNING
When oil that has been used in a diverter switch housing is pumped out,
conducting tubes and hoses that are earthed should be used to avoid the risk of
explosion due to the gases produced by the arcs during service.
CAUTION
Do not fill oil into the diverter switch housing if the transformer tank is under vacuum
and the diverter switch housing is not.
CAUTION
Do not fill oil into the transformer tank if the diverter switch housing is under vacuum
and the transformer tank is not.
CAUTION
Leave a gas cushion on top of the oil in the diverter switch housing.
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