Assembly Instructions / Power2 500-M
4 Installing the low-pressure stage / 4.2 Steps for fastening the low-
pressure stage
© Copyright 2020 ABB. All rights reserved.
HZTL455311P0009_EN
Rev.A
July 2020
4.2
Steps for fastening the low-pressure stage
4.2.1
One-piece foot
Angle-controlled tightening
Due to the special design of the foot of the low-pressure stage, the foot is not in contact
with the bracket in the area of the screw holes as long as the screws have not been
tightened. Initially, the foot only touches the bracket at the centre of the foot. Therefore the
screws must be pre-tightened with the pre-tightening torque before angle-controlled tight-
ening can be used. We recommend tightening the foot screws to the pre-tightening torque
in three steps in a
Z
configuration.
Fig. 5: Z tightening method and minimum contact surface
01
25 % of surface in contact
u
Pre-tighten the foot screws by hand, then tighten with
50 %
and subsequently with
100
%
of the pre-tightening torque.
25 %
of the surface of the screw contact points must be
in contact with the bracket. If the surface contact is not sufficient, the screw must be re-
tightened until
25 %
of the surface rests on the bracket.
u
Perform check using the feeler gauge (
0.05 mm
).
u
Tighten the screws with the specified tightening angle in a
Z
configuration.
Power2
Thread size
[mm]
Pre-tightening
torque
[Nm]
Tightening angle for
tightened height a
[degree]
Additional tighten-
ing angle for every
10 mm of additional
screw length b
[degree]
550 LP
M20
90
33
4.4
Table 7: Fixing screw tightening angle
CAUTION
If the contact points do not touch the bracket before the tightening angle is
applied, the pre-tensioning force will be too small. The screws will loosen
and break. The correct tightening angle results from the length
a + b
and the
thickness of the washer.
Some brackets have through-holes for attaching the low-pressure stage or threads in blind
holes and start only a few millimetres under the contact surface (recessed). To ensure that
the screws still have the same high pre-tensioning force, the tightening angle must be in-
creased by the specified amount for every
10 mm
of additional screw length.
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Summary of Contents for Power2 Series
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