Mechanical seals are offered in single and double configurations and are used for chemical applications where leakage needs to be minimized or eliminated. The single internal mechanical seal is the most common seal type and is ideal for pumping clean liquids up to 5,000 cP viscosity. The double mechanical seal requires a flushing system and is typically used when pumping liquids that are viscous, abrasive, crystalize on contact with air or are very hazardous. Carbon vs. SiC seal faces are the primary choice for most applications up to 500 °F. SiC vs. SiC seal faces have high abrasion resistance and can be applied up to 500 °F. Teflon vs. SiC seal faces have extreme chemical resistance and can be applied up to 180 °F and 50 PSI differential pressure.