Gaskets and bolts lose some load after assembly. PCC-1-2026 J-4 describes when an extra relaxation pass helps, when to do it and when not to. A printable PDF (PB-TD-219) is below. Values are for reference; confirm against the current edition of the governing standard. Send us your bolting list for a quote or call (281) 581-0176.
Related: Flange Tightening Pass Table · Single Stud Replacement Pre-Check · All technical docs
When to specify one
Relaxation passes are for problematic joints or joints without enough load margin per App O (J-4).
Pre-start-up retorque (J-4.1)
- Also called a cold relaxation pass.
- At ambient temperature, after a set time following initial tightening, before the joint goes into service.
- Extra circular pass or passes at target torque.
- Used for PTFE, HDPE and similar gaskets. Testing shows it is not needed for semi-metallic gaskets with flexible graphite.
Start-up retorque (J-4.2)
- When the flange and bolts reach 300–450°F, or within 24 hours of start-up if the joint runs below 300°F.
- Adjust the target torque for the nut factor at temperature.
- Tighten each bolt in a circular pattern until the nuts stop turning.
- Needs a risk assessment. Tightening a pressurized joint carries a blowout risk.
- Typically not recommended for PTFE gaskets.
After a thermal cycle (J-4.3)
Once the joint has been in service and cooled, turn-of-nut, tensioning or relubricating is preferred over plain retorque.
Live tightening (J-4.4)
- After more than a few days at temperature, torque no longer gives an accurate load. Turn-of-nut or tensioning is preferred.
- Not for PTFE at elevated temperature. Limit fiber sheet gaskets to low-pressure, non-hazardous service.
- Needs a risk assessment. See App G for single stud replacement.
References: ASME PCC-1-2026, Guidelines for Pressure Boundary Bolted Flange Joint Assembly. Summaries are paraphrased; clause numbers refer to ASME PCC-1-2026 unless noted. Patriot Bolt manufactures bolting and does not perform bolting, training or joint assembly services.