Rotary Joint Seal Materials: Graphite, SiC and PTFE
The service life of a rotary joint depends largely on its seal faces. Pressure, temperature, speed and media cleanliness all act on this pair of sliding surfaces, so choosing the right seal material often matters more than upsizing the unit. Drawing on DEWEL's production experience since 2006, this article compares three widely used seal materials and the duties they fit.
Why the Seal Pair Defines Joint Performance
Inside a rotary joint, the housing, bearings, seal pair and spring compensation mechanism work together. The seal faces must hold media pressure - DEWEL's high pressure series reaches 138 MPa - while sliding at high speed with minimal leakage. A mismatched material typically leads to early face wear, rising leakage and, in severe cases, seizure.
Graphite: The Proven Choice for High Temperature Duty
Carbon graphite offers low friction and self-lubrication together with excellent temperature resistance, which makes it the mainstream option for thermal oil service. DEWEL thermal oil rotary joints cover typical oil temperatures of 180-320 degrees C, paired with hardened mating faces for long, stable operation. Its limitation is lower mechanical strength: graphite is unsuitable for media carrying hard particles and requires reasonable media cleanliness.
Silicon Carbide: For High Pressure and Harsh Media
Silicon carbide is extremely hard, wear resistant and chemically inert; sintered SiC withstands most acids and alkalis. For high pressure water and hydraulic circuits, SiC-versus-SiC or SiC-versus-graphite pairs are the reliable arrangement. DEWEL high pressure rotary joints rated to 138 MPa generally specify silicon carbide faces to absorb intense pressure and shock loads.
Filled PTFE: When Corrosion Resistance Comes First
Filled PTFE is chemically stable against nearly all acids, alkalis and organic solvents, with a very low friction coefficient. Its wear resistance and temperature ceiling are below graphite and silicon carbide, so it suits corrosive media at ambient to moderate temperatures. Where corrosion resistance is the primary requirement, filled PTFE offers strong value.
Matching Material to Duty: The DEWEL Approach
A practical three-step routine works well. First confirm media and temperature: for thermal oil at 180-320 degrees C, choose graphite against a hardened face. Next confirm pressure: for high pressure duty, specify silicon carbide. Finally confirm media cleanliness: particle-laden media call for hard-on-hard pairs plus enhanced filtration. DEWEL, founded in 2006 in Tengzhou, Shandong, is ISO 9001 certified and supplies a full range from DN6 to DN350, including single passage, double circuit and multi-station designs, with custom engineering available.
Related products: Rotary Joints | High Pressure Rotary Joints | Double Circuit Rotary Joints
