According to ASME PCC-1-2022, Guidelines for Pressure Boundary Bolted Flange Joint Assembly, the correct bolt torquing sequence is critical to achieving a leak-tight joint in piping systems.
Many field failures trace back to skipping the cross-pattern tightening steps. The standard prescribes a four-pass method: first snug all bolts hand-tight, then run a cross-pattern torque at 30%, 60%, and finally 100% of target. Each pass must follow the same numbered sequence around the flange.
A common error is using a single pass to full torque, which creates uneven gasket compression and leads to leaks during hydrostatic testing or service. Auditors typically check the torque sequence documented in the joint assembly procedure and compare it against PCC-1 Annex F.
Key takeaways for welding and piping QC engineers:
• Always specify the bolt tightening sequence in the installation procedure.
• Verify that technicians follow a cross-pattern, not a circular order.
• Use a calibrated torque wrench and record the torque value for each bolt.
• Lubrication per PCC-1 Table 1 reduces friction scatter.
What methods does your team use to verify flange joint integrity on site?
Source: ASME PCC-1, 2022