Pipe Repair Clamp Size Calculator
Determine the appropriate repair clamp length, width, and pressure class for a damaged pipe section based on pipe outer diameter, damage zone length, operating pressure, and pipe material.
Formulas Used
Hoop Stress (Barlow's Formula):
σhoop = (P × OD) / (2 × t)
Maximum Allowable Operating Pressure:
MAOP = (2 × t × SMYS × SF × TF) / OD
where SF = safety factor (0.72 water, 0.60 gas/hazardous), TF = temperature de-rating factor
Design Pressure (ISO 24817):
Pdesign = 1.25 × Poperating
Minimum Clamp Length:
Lclamp = Ldamage + 2 × Loverlap
Loverlap = max(50 mm, 0.5 × OD, 15 × t)
Clamp Shell Thickness (Thick-Wall Cylinder — Lamé):
tclamp = (OD/2) × (√((σallow + P) / (σallow − P)) − 1)
Bolt Torque:
T = K × d × F (K = 0.2 nut factor, d = bolt diameter, F = bolt load per bolt)
Assumptions & References
- Clamp pressure classes follow EN 1092-1 / ASME B16.5 standard ratings: 16, 25, 40, 64, 100, 160, 250, 320 bar.
- Design pressure = 1.25 × operating pressure per ISO 24817:2017 (Petroleum and natural gas industries — Composite repairs for pipework) §6.3.
- Overlap length formula per ASME PCC-2-2022 Article 2.1 (Repair of Pressure Equipment and Piping).
- Safety factors: 0.72 for water/non-hazardous (ASME B31.3 normal fluid), 0.60 for gas and hazardous fluids.
- Temperature de-rating: linear 0.5%/°C above 100°C, capped at 30% reduction; 10% margin below 0°C for embrittlement.
- Clamp shell allowable stress = 138 MPa (carbon steel clamp body, ASTM A105 / EN 1.0460).
- Gasket contact stress target = 20 MPa (elastomeric full-face gasket, ASME PCC-1).
- Nut factor K = 0.2 (lightly oiled bolts, standard assumption per ASME PCC-1-2019).
- Minimum clamp shell thickness = 6 mm regardless of calculation result.
- This calculator provides guidance only. Final clamp selection must be verified by a qualified engineer and the clamp manufacturer's sizing charts.
- Does not account for corrosion allowance, cyclic loading, or soil/external loads on buried pipe.