Flange bolt tightening is often overlooked but is absolutely critical for the success of an anaerobic flange seal. Using the wrong torque—whether under-torquing or over-torquing—will compromise your seal, regardless of how perfectly you applied the sealant.
Anaerobic sealants are designed to cure only in a tight, controlled environment. Improper torque destroys this environment, leading to leaks, damage, and poor sealing integrity.
1. The Dangers of Under-Torque (Insufficient Pressure)
Under-torquing bolts means you don’t achieve the necessary clamping force to properly mate the flanges.
| Problem | Result on the Seal |
| Insufficient Clamping | The flanges do not compress tightly enough, leaving a gap wider than the sealant’s 0.25 mmmaximum limit. |
| Oxygen Trapped | The wider gap traps too much air (oxygen), inhibiting the cure of the anaerobic sealant inside the joint. |
| Poor Seal & Leaks | The uncured or partially cured sealant cannot withstand internal fluid pressure, leading to immediate leaks. |
The Fix: Always consult the manufacturer’s service manual or technical data sheet for the specified bolt torque sequence and value. Use a calibrated torque wrench to ensure the correct clamping force is applied evenly.
2. The Problems with Over-Torque (Distortion and Damage)
Over-torquing bolts is equally destructive, especially on softer materials like aluminum or cast iron.
| Problem | Result on the Seal |
| Flange Distortion | Excessive force warps or bends the flange surfaces, creating uneven gaps and high-stress points. |
| Damaged Surface | On aluminum, over-torquing can damage or gall the mating surfaces, creating deep grooves that the sealant cannot reliably fill. |
| Seal Unevenness | The clamping force becomes uneven, causing the sealant to be extruded out in high-pressure areas while creating too large a gap in low-pressure areas, leading to leaks. |
The Fix: Stick to the specified torque settings. Do not guess or simply “tighten until it feels tight.” Tighten bolts in a cross-hatch pattern and in progressive stages to evenly distribute the stress across the flange.
Incure HeatGrip™ 504 Flexible General Purpose Gasket Sealant for Forgiveness
We recommend Incure HeatGrip™ 504 Flexible General Purpose Gasket Sealant because its cured state offers a degree of flexibility that can slightly accommodate the minor movements and stresses caused by less-than-perfect torquing.
- Flexible Layer: Cures into a flexible plastic layer (5.2N/mm2 compressive strength), which resists blowout and minor flange movement better than fully rigid sealants.
- Optimal Performance: When properly applied and torqued, the 504 ensures a reliable, leak-proof seal up to 150∘Con rigid, machined flanges.
Final Rule: Anaerobic sealant is a chemical gasket that works best in an ideal mechanical environment. Proper torquing is the final step that creates that ideal, tight, oxygen-free environment.