Page 56 - banneredThermosealCatalog2010

Page 2 of 3 Torque to Achieve Bolt Utilization 061207
FOLLOW BASIC GASKET INSTALLATION PROCEDURES:
1. Clean and inspect flanges.
2. Clean and inspect gasket. Make sure the right gasket is used (No substitutes).
3. Install gasket in accordance with instructions for gasket type. Do not apply tape, lubricant
or gasket adhesive unless specified.
4. Check flange alignment for parallel and high-low.
5. Install bolts without driving them in. Friction factors are irrelevant when threads are
damaged.
CONTROL FRICTION:
1. Check threads on the bolt/stud and nut for damage or flaws. Repair or replace the damaged
part. The nut should run on the bolt by hand past the point of travel.
2. If applying lubricant, apply the correct lubricant to the bolt throughout and past the point of
travel. Apply lubricant to nut threads and nut face. When using washers, apply lubricant to
the washer on nut side. Always apply consistently from bolt to bolt. This will affect the
torque value so be sure to re-calculate torque based on reduced friction factor.
Torquing a lubricated fastener using specs for unlubed bolts can cause over-
compression.
3. Use hardened steel washers if specified. The hard surface and increased footprint allow for
uniform load from bolt to bolt.
4. Be sure the bolts align properly in the flange holes. Even slight angles on the bolt will affect
friction, load and relaxation.
TIGHTENING SEQUENCES:
1. Bolt patterns or tightening sequences are used to help pull in the flange and load the gasket
evenly without damaging the gasket. Use star/cross pattern during installation. Clockwise
tightening alone can cause canting of the flange.
2. Following a bolt pattern still creates cross-talk between the bolts. A tightening and
loosening effect takes place in the other bolts as one bolt tightens. Multiple passes are
made during installation and at full torque to counter this effect.
MULTIPLE PASS:
1. For multiple passes, start at a low torque value, usually 20-30% of final torque desired.
Complete the first pass and increase torque to 60-70% and repeat pattern. The third pass
is done at desired torque or 100%. In some cases a 4th and 5th pass is specified, usually for
critical service applications. The fourth pass is at 100% and a chase pattern is used. As if
facing a clock, start at 12 moving towards 3, 6, and 9 and back to 12, tightening each
fastener at 100% of desired torque. Upon completing the fourth pass at 100% of torque,
conduct a 5th pass at desired torque (Chase Pattern), however counter clockwise.