When choosing elastometer seals consider the following: Buna-N is a good all around seal material where temperatures are moderate and there are no specific chemical problems. Viton is more expensive than Buna-N, tends to take a greater compression set than Buna-N, and may seal with somewhat greater difficulty. Viton sealed systems may be baked to a suggested maximum temperature of 150 degrees Celsius. The bakeout temperature using Buna-N is limited to about 80 degrees Celsius. The choice is straight forward: use Viton where temperatures, chemical resistance, or long life make it beneficial. Use Buna-N where temperatures are moderate. Use silicone rubber where highly corrosive or chemical environments exist. Silicone can be used at 200 degrees Celsius, at higher temperature for short periods.
ISO flange components using elastometer seals are primarily designed for use at the subatmospheric pressure. When large numbers of elastometer seals are used without baking, typical limiting pressures may be around 10~7 Torr. Baked systems using Viton can be used to pressures two decades lower. Standard components can be used to a slight over pressure. Use of an overpressure ring will allow pressures up to 100 PSI in some circumstances.
ISO flange components using elastometer seals are primarily designed for use at the subatmospheric pressure. When large numbers of elastometer seals are used without baking, typical limiting pressures may be around 10~7 Torr. Baked systems using Viton can be used to pressures two decades lower. Standard components can be used to a slight over pressure. Use of an overpressure ring will allow pressures up to 100 PSI in some circumstances.