Replacement Of Parts (12-24 Kv); Replacement Of Contact Knife With Draw Bar - ABB NAL Series Mounting And Operation Manual

14.0 Replacement of parts (12-24 kV)

The switch disconnector type NAL is equipped with DMC insu-
lators (glassfibre-reinforced polyester) with self-tapping screws
for fixing of insulators and contacts.
If the same insulator and screws are to be used after exchange
of parts, the following procedure must be followed:
– unscrew the self-tapping screws carefully and brush them
clean, and blow out the small particles in the threaded hole
(use eye protection).
When mounting, the screws must be entered carefully into the
threads in the insulator and tightened with care.
– correct torque, see page 28.
If using a new insulator, the holes should be threaded to about
10 m deep by the self-tapping screw before mounting. Remove
the screw and blow the holes clean.
The mounting takes place according to the following
procedures.
14.1 Replacement of contact knife with draw bar Fig. 69.
Switch-disconnector in open position with both the operating
springs uncharged:
1. Remove the circlips 2.1 attaching the draw bar to the main
shaft (eccentric bolt not to be loosened).
2. Unscrew the screw(s) 2.2 attaching the main contact to the
insulator. Remove the fixed contact with the contact knife
and draw bar (1 pc screw on 12 kV and 2 pcs screws on
24 kV).
3. Attach the new main contact with the contact knife and draw
bar to the insulator.
Fig. 68 Adjustment moving knife
4. Grease the new contact knife with ISOFLEX NCA 52 and
check carefully that it enters the fixed main contact correctly,
and also that the arcing knife moves freely in the arcing
chamber when closing and opening (the arcing knife does
not have the same position related to the contact knife
during the closing and opening movement). The contact
knive must rotate firmly at the pivot point, but without
jerking.
5. Attach the draw bar to the main shaft by the eccentric bolt
2.3 and secure with washer and circlips 2.1.
6. The depth of the engagement between the fixed and the
moving contact can be adjusted by the eccentric bolt 2.3 or
by moving the insulator 2.4.
Fig. 69 Support insulator with knife complete
NAL/NALF – Mounting and operation manual 23