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CDHF-SVN01B-EN
Water Piping
Bolt-Tightening Sequence for
Water Piping Connections
A bolt-tightening sequence for
flanges with flat gaskets or O-rings is
described below and shown in
Figure 19. Remember that
improperly tightening flanges may
cause a leak!
Note: Before tightening any of the
bolts, align the flanges. Flange bolt
torque requirements are given in
Table 7.
Flanges with 4, 8 or 12 Bolts.
Tighten all bolts to a snug tightness,
following the appropriate numerical
sequence for the flange. Repeat this
sequence to apply the final torque to
each bolt.
Flanges with 16, 20 or 24 Bolts.
Following the appropriate numerical
sequence, tighten only the first half
of the total number of bolts to a snug
tightness. Next, sequentially tighten
the remaining half of the bolts in the
proper order.
Table 7 – Flange Bolt Torque Recommendations for O-Ring and Flat-Gasket
Piping Connections (See Note).
Bolt Size
(In)
3/8
1/2
5/8
3/4
Note: Torques provided in Ft./Lbs. (Newton/metres)
Flanges with More than 24 Bolts.
Refer to Figure 19 and sequentially
tighten the first 12 bolts to a snug
tightness. Tighten the next 12
consecutively numbered bolts in
sequence, to the final torque.
Then, apply final torque to the first
12 bolts and the bolts not yet
tightened (i.e., unnumbered bolts in
Figure 19). Be sure to start with bolt
"1" and move progressively around
the flange in a clockwise direction.
Evaporator Water Box Covers.
See Figure 19. Ensure that the water
box head rests tightly against the
gasket or tube sheet; then snugly
tighten the bolts in sequential order.
If excessive tube sheet crown
prevents the head from contacting
the tube sheet, tighten the bolts
located where the greatest gaps
occur. Be sure to use an equal
number of bolt turns from side to
side.
Then, apply final torque to each bolt
in sequential order. (Each bolt is
identified by number in Figure 19.)
Gasket Type
O-Ring
25 (34)
70 (95)
150 (203)
250 (339)
Flat
12-18 (16-24)
33-50 (45-68)
70-90 (95-122)
105-155 (142-210)
33
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