When to specify a torque and tightening sequence?
Based on experience, if the bolts are in a circular pattern, a criss-cross tightening sequence would normally be specified. For non-circular bolt patterns, a spiral sequence starting at the middle would normally be specified (See Dia. B).
How to specify the sequence of tightening bolts?
Specify a Tightening Sequence: The majority of joints consist of more than one bolt and bring together surfaces that are not completely flat. The sequence of tightening bolts can have a major influence on the resulting preloads. With such joints, consideration should be given to specifying the sequence in which the bolts are to tighten.
How to calculate the torque of a flange bolt?
Flange Bolt Torque Sequence 1 PASS 1 Torque Sequence: Torque to a maximum of 30% of the final torque value in accordance with the torque sequence. Check that gasket is getting compressed uniformly. 2 PASS 2 Torque Sequence: Torque to a maximum of 60% of the final torque value. 3 PASS 3 Torque Sequence: Torque to the final torque value (100%).
Why is a square quadrant sequence used for bolt tightening?
Uses the same pattern as the legacy method but allows fewer passes and less overall effort. This is achieved because not every bolt goes through the different torque load amounts. Simpler to follow than the legacy pattern. This pattern follows a square quadrant sequence and is used on flanges with 16 bolts or more.
Why do you need a torque sequence for a flange?
Flange joints require proper tightening to avoid the leak of the fluid from the joint. Bolt tightening sequence or torque sequence is defined in the torque tightening procedure. Most company has their Flange bolt torque tightening procedure that used during construction and operation of the plant.
What’s the torque sequence for a Ford engine?
The torque sequence for all three Ford engines can be seen in the photo above. Again, the 289 and 302 are two-stepped (I do three steps) to between 65 and 72 lb-ft. The 351 develops more compression and horsepower, so it needs more torque on the head bolts.
How many torquing passes in a criss-cross torque sequence?
Torque bolts and nuts in a “CRISS-CROSS” sequence using a minimum of three torquing passes and the maximum bolt stress as defined. PASS 1 Torque Sequence: Torque to a maximum of 30% of the final torque value in accordance with the torque sequence.
What should the torque be on a torque table?
Torque specifications are shown either as an exact figure, or a specific range. Follow any special instructions or multi-step directions carefully to assure correct final torque. There may be different specifications for different size bolts, bolts in different positions, tightening bolts in several stages, or a cold engine vs. a warm engine.