4. Replace the flame element assembly with a new
assembly or properly cleaned and inspected existing unit.
5. Loosen the jacking nuts on the tension rods until the
flame cell assembly seats onto the gaskets.
6. Replace all tensioning studs and tighten the outer nuts
hand tight only. Check to be sure that all the jacking nuts
are completely loose and not making contact with the
flange face.
7. Torque the bolts in sequence as shown in the Torquing
Instruction section.
Torquing Instructions
CAUTION
Excessive or uneven torque can cause
permanent damage to gaskets and housing.
Tools/Supplies Required
• Hand operated conventional torque wrench or
power assisted torque wrench appropriate for the
specified torque.
• Socket wrenches of the proper size to fit the hex nuts
being tightened.
• Molydisulfide based lubricating paste. Heavy-Duty
Lubricating Paste.
• Brush suitable for applying lubricant to the studs.
• Wiping rags necessary for the clean up of
excessive lubricant.
Procedure
1. Use studs and nuts that are free of visible contamination
and corrosion.
2. Apply lubricant to the threads of the stud protruding
outboard of the interior flanges and to the face of the hex
nuts which will contact the flange.
3. Assemble the nuts to the studs such that the amount
of thread extending outboard beyond the nut is
approximately equal on both ends.
4. Tighten the nuts to the torque values shown in Table 1
following the designated sequence, repeating the
sequence as shown. Flange pattern tightening sequences
are shown in Figure 5.
Bolt Lubrication
Lubrication affects required torque of clean fasteners in good
condition more than any other factor. In fact, 90% of applied
torque goes to overcome friction while only 10% actually
stretches the bolt. Table 1 assumes that only machine oil is used
as a lubricant. Table 2 shows a list of several common lubricants
and their effect on torque required to stretch bolts to 50% of their
yield strength. Most are available from local bearing distributors.
MODEL
BOLT SIZE
TIGHTENING STEPS AND TORQUE (FT-LBS / N•m)
1
2
3
4
5
6
DFA-7236
1.50 in.
Snug
80 / 110
250 / 340
450 / 610
700 / 950
1000 / 1360
1. Using machine oil as lubricant. See Bolt Lubrication section on page 7 and torque correction factors for other lubricants in Table 2.
Table 1.
Tightening Steps and Torque Values
(1)
DESCRIPTION
COEFFICIENT OF FRICTION
MULTIPLY TORQUE VALUE IN TABLE 1 BY
Machine Oil
f = 0.15
1.00
API SA2 Grease
f = 0.12
0.80
Nickel-based Lubricant
f = 0.11
0.73
Copper-based Lubricant
f = 0.10
0.67
Heavy-Duty Lubricating Paste
f = 0.06
0.40
Table 2.
Torque
Correction Factors for Common Lubricant
7
Model DFA 7236
North America
Only
