Abstract
Recently, the demand for expanded natural graphite is increasing as a material for the gland packing of valvesin various industrial fields in place of asbestos. This is in response to the needs for longer service life, higher reliability and lower maintenance, as well as restrictions against the use of asbestors. The expanded natural graphite gland packing has the advantages of far less retightening works and a longer service life due to its superior features of sealing and heat resistance. However, there are disadvantages in that the mechanical strength is lower and frictional resistance in movement of the valve stem is higher. To overcome these drawbacks, we have developed a gland packing using graphite pellets of 3-6 mm in diameter made by coating natural graphite with inorganic binder on ceramic core balls of 1-2 mm in diameter based on a new concept.
