Page 171 - Machinery Component Maintenance

Process Muchiner! Piping 153

Table 4-3
Torque Values (Foot-Pounds) to Achieve 40,000 PSI Bolt Stress with
Lubricated Bolts, Nuts, and Bearing Surfaces.
Final Torque
Bolt Initial Intermediate Torque Tension
Diameter (In.) Torque Torque ft-lbs Ibs

518 30 45 60 8,080

%J 40 70 loo 12.080
‘lx 80 120 1 60 16.760

1 I00 170 240 22,040

* NOTE: Use values for joints which contain Aluminum (Type 6061-T6)
jlunps.

been tightened once. Repeat this operation as many times as neces-
sary until the No. 1 bolt torque is not less than 80% of the initial
torque setting after the last crisscross tightening sequence.
Set the torque wrench to the next increment and continue tightening
in the crisscross pattern and resetting until the final torque has been
reached in all bolts. However, after completing the last tightening se-
quence at the final torque setting, the No. 1 bolt torque shall not be
less than 90% of the final torque value. Always use the crisscross
pattern and each tightening sequence must terminate at the last num-
bered bolt.
When a flanged joint is torqued and accepted, a car seal shall be
placed from bolt end to bolt end and both flanges shall be sprayed
with white paint in such a position that it can be seen from grade.

Hot Bolting and Leakage Control
Hot bolting during startup and during process runs has been found to
be an important factor in minimizing flange leakage. During heat-up and
because of temperature changes, the bolts and gaskets deform perma-
nently. This causes a loss of bolt stress after the temperature changes
have smoothed out. Hot bolting helps correct this.