A selection of Metcar shaft packing rings.
A selection of Metcar shaft packing rings.

Metallized Carbon Corporation, a manufacture of oil-free, self-lubricating, carbon-graphite materials for severe service lubrication applications, is promoting its custom radial seal ring assemblies. Also known as packing rings, radial seal rings are used to prevent leakage of industrial blowers, pumps and other turbo machinery by sealing the clearance between a rotating or reciprocating shaft and the stationary housing.

The carbon-graphite radial seal rings manufactured by Metcar meet the most stringent customer specifications, the company claims. More than 150 grades of proprietary carbon/graphite material are available, and Metcar engineers work with customers to select the optimum grade for specific applications, based on the environment, shaft, housing materials, or rotational speed.

Metcar’s packing rings are designed for sealing both liquid and gases for many applications, including aircraft turbine engines, blenders and mixers, furnace exhaust blowers, and oil free piston compressors, as well as ship propeller shafts, steam turbines, and water pumps and turbines.

The carbon-graphite radial seal assemblies help solve serious leakage problems that occur when stuffing box seals fail due to wear, thermal degradation, chemical attack, and dimensional stability problems with leather, plastic, composite or elastomeric elastic seal ring materials.

Two types of radial seal rings are available. The ‘close clearance’ version is a one piece, solid ring made to fit with close clearance on the outer dimension of the rotating or reciprocating shaft. If the shaft is expected to experience thermal expansion, the carbon-graphite ring comes in a version that is shrink-fitted into a metal retaining ring, providing the carbon graphite/metal assembly the same thermal expansion rate as the shaft.