Cam-Profile Gaskets

General Information

Cam-profile gaskets consist of a steel core holding the grooved profile machined into it. This cam profile is then covered with a soft material layer tightly pressed into the grooves.

Thus, a slim layer between the tips of the profile and the sealing area (flange surface) is created.

Cam-profile gaskets are used in refineries, chemical and petrochemical plants. They are well suited for sealing of flanges with high pressure and thermal demands.

Cam-profiles

We offer cam-profile gaskets in various designs. There are versions without centering rim (center ring), with fixed centering rim (MMD-GG-FG-CR) and with loose centering rim (loose center ring) (MMD-GG-FG-LC). In EN 1514-6 and EN 12560-6 the versions without centering ring are designated with NR, the ones with turned centering ring with IR and those with loose centering ring with LR. If this designation is added to the type designation, it can immediately be seen that this is a gasket for standardized flanges.

For large temperature differences between the inner and outer diameters and for gaseous media, it is advisable to use a gasket with a loose centering ring or with a predetermined breaking groove in the centering ring for stress compensation and to reduce resonance vibrations and the associated risk of spontaneous fractures. For non-rigid flanges, the use of cam-profiles with support ring (MMD-GG-FG-BUR-FF) is recommended. Cam-profile gaskets without supports should not be used. The cam-profiles yielding under thermal alternating stresses can lead to a failure of the sealing system after only a few load changes (e.g. by starting and stopping the systems).

In general, cam-profile gaskets with layers (MMD-GG-FG) made of PTFE or graphite are used. Metallic layers of silver or aluminum are also used at very high operating temperatures. Cam- profile gaskets with soft-material layers are characterized on the one hand by a very low minimum surface pressure, which is determined by the material of the layer. On the other hand, the amount of the maximum tolerable surface pressure is very high, since this is determined by the value of the metallic carrier material. Cam-profile gaskets cannot adapt to the flange blade inclination/rotation (warped flanges). The inner cams are turned lower in order to obtain the support up to the gasket center. The more compacted support in the center of the gasket results in a kind of cushion over which the flange can tilt.

Soft-material layers

The cam-profile gasket with supports provides the user with a gasket that can hardly be surpassed in the variety of possible applications combined with outstanding application safety. Depending on the layer thickness, usually 0.5 mm for graphite, density D = 1.0, the carrier material receives precisely defined cam-like grooves. The soft material layer is applied with a low chloride material, which is used as an adhesive due to its high adhesive strength. During assembly, the material of the soft layer presses itself into the cam valleys of the carrier material. The support and carrier are matched to each other in such a way that the cam tips are still completely covered with the material of the support in the operating state. The soft material overhang should be approx. 0.10 mm. Metallic contact and the associated risk of scoring in the flanges are avoided. The flow behavior of the soft material is largely suppressed by the chambering of the support material in the grooves. This makes it possible to use the advantages of PTFE even under high pressures. In contrast to graphite layers, a smaler thickness must be selected for PTFE layers because their higher material density means that they cannot be compressed as much. A thickness of 0.35 mm with a density of D=1.0 or 0.5 mm ePTFE has proven its worth. If this is not done, the soft material overhang for PTFE is approx. 0.2 to 0.3 mm. The result is the same flow and setting behavior as with PTFE flat gaskets. The current standards EN1514-6 and EN 12560-6 also require a layer thickness of 0.5 mm for PTFE.

Incorrectly selected layer thicknesses lead to leakages, but at least to loosened screw connections. They therefore pose a danger to the sealing system. The geometry of the cam-profiles is also standardized in such a way that it cannot be manufactured. A radius of 0.0 mm in the cam base, as required by DIN EN 1415-6, cannot be produced by the machines. The standard urgently needs to be revised. Many manufacturers use a "free" geometry or produce according to the old DIN 2697, which can lead to expensive leaks.

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