Manufacturing requires not only assurance of equipment durability, but safety as well. For this reason, most companies utilize a bolt tightening sequence in production. But what is a bolt tightening sequence? Aside from professional engineers, few know or understand the process. Let’s break down the importance and process of a bolt tightening sequence.
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What’s a Bolt Tightening Sequence?
Bolt tightening sequences are when an arrangement of bolts is tightened in a predefined order. Each bolt is tightened in turn until the desired tightness or final torque is reached. Most companies use their own bolt tightening sequence during construction and operation and are typically secured with the help of a torque wrench (manual or hydronic wrench).
Why Does Bolt Tightening Matter?
Using this technique guarantees pressure is distributed equally between the bolts, thereby reducing any potential warping, loss of pre-load in a bolt, or damage to the gasket.
The bolt tightening sequence also secures parts from coming loose, mitigating any risks of equipment damage and delay in daily operations.
What Bolt Tightening Sequence Works Best?
Every manufacturing company should have a standard bolt tightening sequence, but the most used and trusted method is the is the Flange bolt torque tightening sequence.
Here’s what the Flange sequence looks like:
The Flange bolt tightening sequence proceeds by turning each bolt and crossing to its opposite in a “Criss-Cross” pattern. Unlike individual bolt tightening, this method evenly applies pressure to limit the risk of breaking bolts.
Proper placement of gasket and bolt tightening ensures leak-free joints in transportation of high-pressure substances. Prior to bolt tightening, be sure to review these points to inspect your flange and gasket material quality:
- Check that flanges are parallel and co-axial before inserting the gasket between the pipe flanges or installing bolts.
- Flange faces must be aligned to the design plane within 1 mm in 200 mm (1/16 in./ft) measured across any diameter; bolt holes must be aligned within 3 mm (1/8 inch) maximum offset.
- Properly clean all gasket seating areas before inserting the gasket, and re-serrate if initial serration is damaged.
- Ensure the gasket used is the correct dimension and specified material.
- Locate gasket correctly to ensure full sealing as indicated below.
- Inspect gasket in advance to check for defects like heat warping.
Flange Bolt Torque Sequence
After completing all pre-checks, follow the pre-defined bolt tightening sequence:
- PASS 1: Torque to a maximum of 30% of the final torque value, checking that gasket is compressing uniformly.
- PASS 2: Torque to a maximum of 60% of the final torque value.
- PASS 3: Torque to the final torque value (100%).
After completing the 3 passes, repeat Flange bolt tightening sequence one more time until rotation stops.
Select from Breiner Innovative for Your Gasket Needs
Whichever bolt tightening sequence your company uses, trust in Breiner Innovative to customize safe and reliable solutions for your company’s equipment. To learn more or secure a personalized, cost-effective and dependable service, contact us today!