Kammprofile gaskets: Sealing solutions for high pressure and high temperature working conditions

1. Structure and working principle
The core of Kammprofile gaskets lies in the synergy of its multi-stage sealing mechanism. The metal core is usually made of 08F low carbon steel, 304/316 stainless steel or titanium alloy, and is formed into a 0.2-0.5mm high concentric serration structure (tooth density is usually 4-8 teeth/cm) through precision stamping or turning. These serrations form microscopic sealing units, which produce two sealing effects under the action of bolt preload: the metal tooth tip first undergoes plastic deformation (deformation of about 15-25μm) to form a mechanical interlock with the flange surface; at the same time, the tooth valley area remains elastic, providing uniform support pressure for the covered flexible material (such as graphite or PTFE).

Pressure-temperature adaptation is a unique performance of toothed gaskets. When the system pressure rises to the working value (up to 42MPa), the serration structure deforms elastically to compensate for the slight separation of the flange surface; when the temperature changes (-200℃ to +800℃), the different thermal expansion coefficients of the metal and the sealing material complement each other: the metal core provides thermal stability, while the flexible layer fills the micro-gaps caused by thermal deformation

Surface interaction is crucial to the sealing effect. The geometric parameters of the serrations (tooth angle is usually 90°-120°) are calculated to ensure that the required surface pressure (generally required to be >70MPa) is achieved under the minimum bolt load. The special dual hardness design - the metal core hardness (HV200-300) is higher than the flange material (HV150-200), while the flexible layer is softer (HV10-30) - forms a hardness gradient, which not only protects the flange surface, but also ensures that the sealing material fully flows to fill the microscopic unevenness. This design allows the gasket to achieve the same sealing effect with only 60% of the bolt load of traditional flat gaskets.

The failure prevention mechanism reflects deep engineering thinking. The concentric layout of the saw teeth forms multiple "sealing lines of defense". Even if local material aging or mechanical damage occurs, the remaining tooth rings can still maintain basic sealing functions. Some high-end designs use asymmetric tooth profiles (sharp front tooth angles for initial sealing, gentle rear tooth angles for long-term retention), which extends the life of the gasket by 3-5 times. Pressure vessel tests show that this structure still maintains more than 90% of the initial sealing performance after 20,000 thermal cycles.

2. Material Science and Engineering Selection
The selection of metal core materials is based on the principle of working condition adaptation. Low carbon steel (such as 08F, SPCC) is suitable for general oil systems (temperature ≤400℃); 304/316 stainless steel is suitable for corrosive media (resistant to CL⁻ ion concentration of 100ppm); Inconel 600/625 or titanium alloy is used for high temperature conditions (≤800℃); Hastelloy or Monel 400 is used for extreme environments. Specially treated metal surfaces (such as tin plating, silver plating or chemical passivation) can further reduce the friction coefficient (μ≈0.08-0.12) and facilitate installation and positioning.

The material evolution of flexible sealing layers shows a trend of refined functions. Expanded graphite (carbon content ≥99%) is the first choice for high temperatures due to its excellent resilience (compression rate 40-60%, rebound rate >25%); PTFE (polytetrafluoroethylene) dominates the chemical industry with its excellent chemical inertness (resistant to almost all strong acids and alkalis); new composite materials such as graphite/metal foil (such as Flexicarb) perform well in the main circulation system of nuclear power plants. The newly developed gradient sealing layer (such as outer layer PTFE anti-sticking, middle layer graphite sealing, inner layer metal mesh reinforcement) enables a single gasket to adapt to complex multiphase flow conditions.

Special coating technology improves marginal performance. The plasma-sprayed Al₂O₃/TiO₂ ceramic layer (thickness 50-80μm) extends the gasket's particle erosion resistance life by 10 times; PFA (perfluoroalkoxy resin) impregnation treatment can reduce the cold flow tendency of PTFE by 70%; and the metal nanowire (such as Ag/Cu) network between graphite layers significantly improves thermal conductivity (up to 80W/m·K) to avoid the formation of local hot spots. These innovations enable modern toothed gaskets to work reliably in extreme ranges from LNG ultra-low temperature (-196℃) to cracking furnace ultra-high temperature (+1000℃).

3. Performance advantages and engineering value
Compared with traditional flat gaskets, the sealing efficiency of toothed gaskets is significantly improved. Under the same bolt load, its leakage rate is reduced by 2-3 orders of magnitude (from 10⁻² to 10⁻⁵mbar·L/s); the flange thickness required to achieve the same sealing level is reduced by 30-40%, which directly reduces the equipment manufacturing cost.

Safety margin design protects key systems. The multiple sealing tooth structure (main sealing tooth + secondary elastic tooth + emergency metal contact tooth) adopted in the main steam system of nuclear power plants can maintain basic barrier functions even under extreme accident conditions.

System adaptability solves engineering problems. The elastic compensation tooth design for the slight unevenness of the flange surface (≤0.1mm) avoids expensive flange reconstruction; special-shaped tooth gaskets (oval, square ring, etc.) perfectly match non-standard equipment.

4. Application technology and installation specifications
Selection calculation is the basis for successful application. The following parameters need to be comprehensively evaluated:
Design pressure/temperature (including fluctuation range)
Medium characteristics (corrosiveness, particle content, phase change)
Flange standards (ASME, DIN, JIS, etc.) and sealing surface types (RF, FF, etc.)
Bolt specifications and preload control methods (torque method, hydraulic tension, etc.)

Preload management is the key to long-term sealing. It is recommended to tighten in stages:
Initial pre-tightening: 30% of the target value, in a cross-cross order
Secondary tightening: 80% of the target value, check the uniformity of the flange gap
Final tightening: 100% of the target value + hot tightening (for high temperature systems)