© SPX FLOW, Inc.
Form No. 1000623
Rev. 6 Jan. 10, 2017
Tightening a Flanged Joint
This procedure outlines the basic steps to torque-tighten a flanged joint with a TWHC hydraulic
torque wrench. It is important that personal protective equipment (gloves, footwear, safety helmet,
eye protection, etc.) is worn at all times by the operator and any other personnel in the work area.
The torquing procedure uses a single hydraulic torque wrench to accurately achieve a predetermined
residual bolt stress.
WARNING: Before bolt torquing, verify that:
• The procedure and data to be used is authorized by a responsible engineer.
• The joints/pipework being worked on are not live. Joints must be at zero pressure and free
from hazardous substances.
• The torque value selected must be based upon the lubricant applied.
Procedure
1. Working in a crisscross pattern, number each bolt in order of torque sequence.
2. Square up the flanged joint using hydraulic torque wrenches, if necessary.
3. Set the pump at its lowest possible output, 103 bar (1,500 psi), and following the numbers on the
bolts, apply the minimum torque to the bolts.
4. In the same tightening sequence, apply approximately 25% of the torque value specified in the
torque data.
5. In the same tightening sequence, apply approximately 50% of the torque value specified in the
torque data.
6. In the same tightening sequence, apply the full torque value specified in the torque data.
7. Working in a clockwise (or counter-clockwise) direction, make a final pass around the flange,
tightening each bolt to the full torque value specified in the torque data.
8. Using a hammer, “ring” each nut to verify that each bolt has been correctly loaded and that no slack
bolts remain.
Loosening Bolts
Loosening bolts using hydraulic torque wrenches can be unpredictable and often unsuccessful,
especially if the nuts and bolts are severely corroded. However, some measures can be carried out to
increase the success rate of nut breakout:
• In general, loosening mildly rusted bolts requires up to twice the makeup torque to release the nut.
Heavily corroded bolts may take up to three times the makeup torque. Verify that the bolt and nut
material is strong enough to accept these higher torques.
• Remove surface rust and scale using a wire brush. Apply releasing oil to the nut, bolt, and bearing
face, and allow time for the release oil to soak in and penetrate.
• Only use the hydraulic torque wrench to break the nut free. Using the torque tool to wind the nut
from the bolt can induce high torsion and reaction forces. Therefore, it is better to use an impact
wrench to completely remove the nut.
• Never strike the torque wrench or nut/bolt in an attempt to 'shock' the nut free. This can cause
damage to the hydraulic torque wrench and operator injury. Evidence of torque wrench abuse will
void the Manufacturer's Warranty.
NOTE: Should maximum pump pressure be reached, and the nut has not broken free,
use a higher capacity hydraulic torque wrench (if the nut/bolt material will accept the
Operating Instructions continued