Clamping ring

The clamping flange is a precision technical solution for securely assembling large bolts using simple hand tools. It achieves high preloads through controlled torque values and appropriate lubricants.

1. Operating Principle

Torque is applied to the bolt or nut using a wrench to generate the required clamping load. Tensioning is achieved by tightening the pressure screws according to defined procedures, with lubricants adapted to friction forces.

The clamping force, in response to the preload, is the force acting on the assembled parts.

For more information on recommended procedures and lubricants, please contact the Technical Department.
Frette de serrage — diagramme technique annoté
Technical diagram — Clamping flange with tightening method annotations

2. Advantages of the clamping flange

  • Finer clamping, distributed across each thread pitch
  • Uniform distribution of pre-stress force
  • Increased overall capacity of the bolted assembly
  • High clamping force
  • Regular tension between studs
  • High clamping precision
  • No heavy tooling required
  • Higher preload for the same screw size
  • No difficult disassembly operations

3. Why choose the clamping flange?

In demanding industrial assemblies — particularly for large bolts used in metal structures, pressure equipment, or production machinery — the clamping flange offers an unparalleled precision/ease of use ratio. It reduces the risks of under-tightening or over-tightening, two common causes of mechanical failure.

4. Complete Application — VDI 2230 Method

What is the VDI 2230 method?
A German standard, a global reference for bolted joint calculation. It precisely determines the torque to be applied to each screw to ensure the long-term integrity of the assembly, without risk of loosening or breakage. Used in the automotive, aeronautical, and petroleum industries.

📋 Assembly Data — M10×26 (15 screws)

Parameter Symbol Value Unit
Flange material — 42CrMo4 (heat-treated) —
Flange yield strength Rₑ(f) 900 MPa
Number of screws n 15 —
Screw type — CHC M10×26 ISO 4762 —
Screw strength class — 8.8 —
Screw yield strength Rₑ(v) 640 MPa
Tensile stress area Aₛ 58.0 mm²
Utilization factor α 0.90 —
Torque factor K 0.18 —

Step 1 — Allowable preload per screw

Fᴹ = 0.90 × 640 × 58.0 = 33,408 N ≈ 33.4 kN per screw
Total Force (15 screws): 15 × 33,408 = 501 kN

Step 2 — Tightening torque

C = 0.18 × 33,408 × 0.010 = 60 N·m per screw

Step 3 — Tightening sequence (15 screws)

1 → 8 → 15 → 7 → 14 → 6 → 13 → 5 → 12 → 4 → 11 → 3 → 10 → 2 → 9
Pass % Torque Objective
1 30 % 18 N·m Contact tightening
2 70 % 42 N·m Pre-tightening
3 100 % 60 N·m Final tightening

5. Summary — M10×26 (15 screws)

Result Value Status
Preload per screw 33.4 kN ✅
Total flange force 501 kN ✅
Tightening torque 60 N·m ✅

6. VDI 2230 Application — New Clamping Flanges

Common assumptions: Class 8.8 (Rₑ = 640 MPa), α = 0.90, K = 0.18 (steel/steel, no lubricant). All screws are fully threaded — engagement length corresponds to the threaded length under the head.

🔩 Flange 1 — 13 M8×22 screws — Class 8.8

Parameter Value Unit
Tensile stress area Aₛ (M8, p=1.25) 36.6 mm²
Preload per screw — 0.90 × 640 × 36.6 21,082 N ≈ 21.1 kN N
Total force (13 screws) 274 kN kN
Torque — 0.18 × 21,082 × 0.008 30 N·m N·m
Min. engagement length (1.5 × 8) 12 mm mm
Threaded length under head (fully threaded screw) 22 mm ✅ mm
Sequence (13 screws, skip 6): 1→7→13→6→12→5→11→4→10→3→9→2→8
Passes: 9 N·m → 21 N·m → 30 N·m

🔩 Flange 2 — 10 M10×34 screws — Class 8.8

Parameter Value Unit
Tensile stress area Aₛ (M10, p=1.5) 58.0 mm²
Preload per screw — 0.90 × 640 × 58.0 33,408 N ≈ 33.4 kN N
Total force (10 screws) 334 kN kN
Torque — 0.18 × 33,408 × 0.010 60 N·m N·m
Min. engagement length (1.5 × 10) 15 mm mm
Threaded length under head (fully threaded screw) 35 mm ✅ mm
Sequence (10 screws, skip 5): 1→6→2→7→3→8→4→9→5→10
Passes: 18 N·m → 42 N·m → 60 N·m

🔩 Flange 3 — 15 M12×28 screws — Class 8.8

Parameter Value Unit
Tensile stress area Aₛ (M12, p=1.75) 84.3 mm²
Preload per screw — 0.90 × 640 × 84.3 48,557 N ≈ 48.6 kN N
Total force (15 screws) 729 kN kN
Torque — 0.18 × 48,557 × 0.012 105 N·m N·m
Min. engagement length (1.5 × 12) 18 mm mm
Threaded length under head (fully threaded screw) 30 mm ✅ mm
Sequence (15 screws, skip 7): 1→8→15→7→14→6→13→5→12→4→11→3→10→2→9
Passes: 32 N·m → 74 N·m → 105 N·m

7. Comparative Table — 3 Clamping Flanges

Flange Num. screws Fᴹ / screw Total force Torque Threaded L. / min. Status
M8×22 cl. 8.8 13 21.1 kN 274 kN 30 N·m 22 mm / 12 mm ✅
M10×34 cl. 8.8 10 33.4 kN 334 kN 60 N·m 35 mm / 15 mm ✅
M12×28 cl. 8.8 15 48.6 kN 729 kN 105 N·m 30 mm / 18 mm ✅
Methodological note: For an even more rigorous study, the complete VDI 2230 method integrates assembly rigidity, preload losses due to relaxation, dynamic external loads, and thermal effects. The values presented form a solid basis for the vast majority of common industrial applications.