High-Temperature Gaskets: Graphite, PTFE, Ceramic and Aramid
Which refractory material suits which temperature and which fluid.
The temperature limit of each material
Cellulose gaskets work to about 120 °C, aramid to 250 °C, PTFE to 260 °C, expanded graphite to 450 °C and ceramic fibre to about 1260 °C. Select on the line's real peak temperature, not its average.
Graphite for steam and hot oil
Expanded graphite, with or without a steel insert, is the most widely used flange gasket in steam and thermal-oil lines. Its broad chemical resistance and good conformability give a reliable seal even at high pressure.
PTFE for chemicals
PTFE reacts with practically nothing and has a very low friction coefficient. Its limitation is creep under sustained pressure; filled grades are used for high-pressure flanges.
Don't confuse insulation with gaskets
Rock wool, fibreglass and ceramic blanket insulate the outside of equipment; they do not seal between two flanges. The two uses are entirely different and not interchangeable.