Mechanical Seal Ring Materials require high strength and a relatively high modulus of elasticity to with stand deformation at the interface. Carbon-graphite seal materials provide the strength and rigidity which are especially important in high pressure , high vacuum , high temperature and zero leakage mechanical end-face seals. High thermal conductivity is essential in removing heat from the interface.

Pure carbon graphite is strictly speaking a ceramic material , but in the form that it is used for seals it will usually be impregnated with other materials that are provided to variously improve the sealing. By reducing porosity , wear performance or strength is increased. it is widely used , not only as one of the face pair on the vast majority of mechanical seals , but also found as the most popular material for segmented circumferential seals and for piston rings in dry or marginally lubricated conditions.

Impregnation of carbon seals can be done with a variety of materials to control permeability. in addition to thermoset resins , other types of impregnants include thermoplastics , metals and inorganic salts or glasses. The temperature limit of the impregnant places an upper limit on the operating temperature of the carbon parts.

Metals such as antimony , silver , copper , nickel and babbitt can improve the strength , thermal conductivity , and tribological characteristics of the materials. Impregnants made of inorganic salts usually phosphate or borate - and glasses are used in high temperature applications. Carbons impregnated with soluble salts must be handled carefully to avoid exudation , especially under humid conditions , but loss of impregnant rarely affects any physical property of a seal other than permeability.

Mechanical seal primary rings can be supplied as per customer drawings and specifications. The rings can be supplied plain , shrink fitted or cemented in metal retaining rings. Mechanical seal rings can also be supplied with the sealing face lapped flat to one helium light light band.

Carbon Seal Ring

Solid Carbon Rings : Normally the seal rings are used in solid form machined from suitable size of carbon blank. The Shape and size of the rings vary according to the design of mechanical seals which are designed for its respective operating conditions. Since carbon - graphite are stable at high temperature , majority of the seal ring designs consitute solid rings.

Cold Pressing : For a cold press fit in steel , where the application is lower than 100^o C steel housings made to H7 bore tolerance are normally recommended. if the housing material has a higher coefficient of thermal expansion than steel the temperature limitation is normally lower. When pressing bearing into its housing a mandrel with collar whose diameter is approximately three tolerances be low the drilling tolerance of the carbon bearings as supplied should be used to press the bearings in. the bore diminishes by 70 - 80% of the pressing over dimension according to the quality and dimension of the housing.

Shrinking : We Recommend shrinking carbon seal rings directly into the metal housing which are to be used at operational temperatures of over 100^o C. To shrink in the bearings , experience has shown that the tolerance overlap should be in the range corresponding H7 / x8...z8. The selected Heating temperature for mounting must be sufficiently high to allow the cold bearings to be easily inserted. On shrinking the carbon bearing bore diminishes by approximately 80...100% of the shrinking overdimension. in the case of the above mentioned shrink fits H7 / x8...z8 this diminishes according to the wall thickness ratio. in order to keep to exact tolerances it is advisable to machine the bearing bore to size after shrinking.

Adhesives : Adhesives are only suitable for bearings which are subject to low temperatures ( up to 200^o C ). Bonding to the housing with commercially available adhesives is possible.for higher temperatures , thermal setting adhesives should be used.

Suitable :Plain Steel , alloyed steel (Chrome Steel) , Hard Metal , Ceramic & glass.
Suitable under certain conditions :Nonferrous heavy metal , chrome nickel steel , chromium plate materials.
Unsuitable :Aluminium and its alloys.

The Surface Quality of the Counter Face Materials has an important influence on the durability of carbon and graphite. Counter face surfaces with a maximum surface roughness of Sr <1 Mm are recommended. For high pressure lapped and superfinished counter faces with a maximum surface roughness of Sr<0.5 Mm are necessary.