Definitions

Adsorption (AD)

The adhesion of gaseous molecules, in extremely thin layers, to the surface of a solid. This adhesion is brought about by the imbalance in forces existing between the solid and the gaseous molecules. These attractive forces are known as Van der Waals forces.

Activated Carbon

Is a form of carbon which is extremely porous with little, if any, volatile material remaining in its structure. Activated carbon is different from activated charcoal. Activated charcoal has a relatively large amount of volatiles remaining in its structure.

Absorption (AB)

To take in and make a part of the whole; to soak up.

Vacuum Level

The term vacuum is used to denote the a pressure below atmospheric. In referring to a "vacuum" it must be noted that it is the opposite of pressure; a high vacuum means a low pressure. A high or deep vacuum is farther from atmospheric pressure than a low vacuum, e.g. a low vacuum is near atmospheric pressure. Absolute vacuum, zero absolute pressure, as measured at sea level is 0 mm of mercury (0mm HgA or 0 Torr), or 29.92 inches of mercury (29.92" HgV). A standard efficiency activated carbon systems is regenerate at 74mm of mercury (74mm HgA) which is equal to 27 inches of mercury vacuum (27" HgV), or 90% of a absolute vacuum.

Vacuum Capacity

The volume of vapor/air removed by the vacuum system at a specified vacuum level. The vacuum capacity is usually measured in actual cubic feet per minute at a vacuum level.

Emission Limits

In North America the emission limits are usually defined in terms of mass of hydrocarbon emitted per volume of liquid loaded at the loading rack, 80mg/l, 35mg/l, or 10mg/l (milligram of hydrocarbon per liter of product loaded). This is an average measurement and must be tested for over a period of time. The U.S. E.P.A. specifies a six hour test as a minimum. In European Union (E.U.) the majority of the countries have adopted a mass emitted per volume emitted. Typically this is 35 grams of hydrocarbon emitted per normal cubic meter vented (35g/Nm3). The older United States standard of 35mg/l is roughly equivalent to the E.U. standard of 35g/Nm3. In Germany, a member of the E.U., the standard of 150mg/Nm3 has been adopted. This standard, known as the TA Luft is considerably more stringent than the other emission limits mentioned.