TIGHTNESS CHARACTERISTICS OF PACKINGS

The demands on industry to reduce fugitive emissions are increasing, steadily /1/, /2/. On this background it is necessary to improve function and tightness of tightening joints like flanged joints and stuffing box packings. Function and tightness can only be guaranteed if the entire chain of parameters involved is taken in to account (design criteria, gasket factors, calculation, mounting procedure). On the field of flanged joints there are standardization projects on the way that address the topics of the new regulatory demands. Only few work is done regarding stuffing box packings, however. Similar to flanged joints a reliable function and tightness of stuffing box packings can only be achieved if the behaviour of the parts (bolts, gland, stuffing box) is known and their interaction is understood. Regarding the behaviour of stuffing box packing materials it is necessary to determine characteristics like deformation capability, relaxation, friction and leak rate. These characteristics have to be used to prove function and tightness. Some attempts to define these characteristic values have already been made; test procedures and test rigs to determine these values have been developed. Parallel to that, gasket manufacturers are developing new packing materials and entire packing sets in order to meet the more stringent requirements on tightness. One of these newly developed products are nonwoven packing sets which should be applicable up to temperatures of 280 °C in the processing and chemical industry. In the paper the most relevant packing material characteristics and the necessary tests to determine these characteristics are reviewed, first.