Packing for the pulp and paper industry

Compression packings used in the pulp and paper industry have been evolving with the utilization of PTFE, aramid, and expanded PTFE-graphite based packings, in an attempt to obtain better control of the leakage around rotating shafts, to extend the period of time between adjustments and to reduce down time. All these types of packings have very good single characteristics that are necessary in order to be able to perform under the different kinds of fluid at the operating conditions encountered in the pulp and paper industry. Nevertheless, none of them have all the desired characteristics. A new type of packing construction has been developed, based on a combination yam where an aramid filament reinforcement is totally covered with an outer jacket of expanded PTFE-graphite layer. Upon braiding this yam, the resultant packing provides a substantial increase in mechanical strength, in comparison with yam not containing the aramid core. The jacket of expanded PTFE-graphite ensures high chemical resistance, self-lubrication, low coefficient of friction and high heat dissipation. This offers an excellent combination of characteristics in one packing.