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ABOUT FLANGES   Revised: 11/07/2013

Intro 4 Bolt 5 Bolt 6 Bolt 8 Bolt 12 Bolt 16 Bolt 20 Bolt 24 Bolt 28 Bolt 32 Bolt

BOLT TIGHTENING SEQUENCE FOR API FLANGES.

Flange Bolt Tightening Sequence Chart, Pamphlet, Booklet

Lubricate bolt and nut threads and nut bearing face (where it contacts the flange).

After flange assembly and all nuts have been run down by hand, start wrench tightening following the sequence of the numbers indicated (marking the number on the flange with a crayon aids in keeping track of the tightening process).

During all of the following steps, keep any gap between flanges even all around the circumference, and nuts made up approximately the same amount on each end of the bolt.

  • First time around just snug the nuts with a hand wrench.

  • Second time around tighten the nuts firmly with the same wrench.

  • Third time around apply approximately 25% recommended torque.

  • Fourth time apply approximately 75% of recommended torque.

  • Fifth time around, apply 100% of recommended torque.

  • Repeat this process until nuts do not move under 100% recommended torque.

  • If possible, re-torque after 24 hours. Most of any bolt preload loss occurs within 24.

 Revised: 11/07/2013

For a Flange Gasket, Bolt and Torque Reference Chart, Click Here.

For flanges with more than 32 bolts, tighten the bolts in groups of 3 adjacent bolts following the sequence for a 12 bolt flange.

For flanges with 40 or more bolts, tighten the bolts in adjacent groups of 4, bolts sequenced as the number of bolts divided by 4. Follow this same rule for all flanges with 40 or more bolts. The best source for guidance in the matter of bolt tightening sequence for flanges is ASME PCC-1. To obtain a full copy of ASME PCC-1, latest edition, go to http://www.techstreet.com/standards/asme/pcc_1_2010?product_id=1675775 .

For more information about Flange Make-up, Standoff / No Standoff and Drift, Click Here.

To learn about how much stud should extend above nuts, Click Here.

To learn about bolt tension for surface and subsea make-up, Click Here.

For a Catalog for Bolts, Nuts, Ring Gaskets and Wrenches, Click Here.

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