Repairs And Adjustments; General; Serial Number; Oil Leakage - ABB VUBB User Manual

7. Repairs and adjustments

7.1 General

Repairs on the VUBB tap-changer fall into two categories:
Repairs – Replacing worn or end-of-service-life parts
Modifications – Improving the already very high standard of
reliability and taking actions to prolong the service life of the
equipment. Modifications may only be as issued by ABB.
The modifications fall into two areas:
Immediate – The modification is to be made at the earliest
possible opportunity.
Routine – The modification is to be made during routine
service.
WARNING
When oil that has been used in a selector switch
housing is pumped out, all tubes and hoses that can
conduct electricity must be grounded to avoid the
risk of explosion due to the gases produced by arcs
during service.

8.1.1 Serial number

Before consulting ABB for technical advice, for assistance
with repairs, to order consumables or to complete repairs,
the tap-changer serial number must be available. The serial
number can be found on the rating plate on the motor-drive
mechanism and on the flange of the selector switch housing
(see Section 2.19).
The serial number must be stated in all
correspondence with the manufacturer. Failure to use
the serial number may cause delays.

7.2 Oil leakage

7.2.1 General
This instruction is a guide in dealing with oil leakage from
the tap-changer. Leakage might be caused by one of the
following:
– Damaged O-ring at the top cover of the tap-changer.
– Leakage between the bevel gear flange and the transformer
cover.

7.2.2 Tools required

Standard set of metric combination wrenches.

7.2.3 Materials and spare parts required

– O-rings
– Grease for ball bearings (Section 3.3).

7.2.4 Procedure

WARNING
Before any work is carried out on the tap-changer,
make sure that the transformer is disconnected and
that grounding is properly executed. Obtain a signed
certificate from the engineer in charge.
CAUTION
Be aware of the risks of slipping due to oil leakage.
Protect the tap-changer from water.
1. Check if oil is leaking anywhere else than from the tap-
changer.
The following procedure applies to all connections other than
the connection between the bevel gear and the top cover.
2. Retighten the nuts at the top of the cover. Tightening
torque 84 ±10 %. See Fig. 66.
Fig. 66. Bolts on top cover.
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