Vacuum Lifting Glossary

A

Abrasion resistance

In the context of vacuum systems, abrasion resistance refers to the suction cups’ resistance to stress – especially friction. The shape of the suction cups and its material properties contribute to its abrasion resistance.

Absolute pressure

A vacuum pressure measured relative to a perfect vacuum (0 torr, PSI or bar) – regardless of the ambient air pressure – is called an absolute pressure.

Ambient pressure (atmospheric pressure)

The ambient or atmospheric pressure is the upper reference point of any vacuum pressure, which is by definition significantly lower. Hydrostatic pressure (as measured in units of mercury by a barometer) is affected by weather and altitude, but the standard atmospheric pressure at sea level is 14.7 PSI, 760 Torr/mmHg (29.92 inHg) or 1,013 millibars. The actual ambient pressure will however influence the maximum vacuum value that can be achieved.

Atm

The unit used for describing any multiple of the standard atmospheric pressure at sea level is atm (lower-case).

B

Bar

From the Greek baros for weight or burden, bar is a metric unit of pressure equal to 100,000 Pascal (100 kPa). In a vacuum system, mbar (as in millibar, one thousandth of a bar) is the more common subunit.

Bernoulli’s principle

Bernoulli’s principle states that the speed of a fluid (or a gas such as air) determines

the amount of pressure that it can exert. When the air accelerates out of a suction cup, the static pressure falls, and a vacuum is produced.

Bourdon-tube gauge

The Bourdon-tube gauge is the most commonly used pressure gauge since the 19^th century.  It’s a mechanical gauge that includes a (Bourdon) tube in the shape of an arc. Pressure will bend the arc relative to the ambient pressure, which actuates an attached dial via a set of gears and springs.

C

Control pressure range

The range between the lowest required and the highest permissible control pressures for a vacuum system to operate correctly.

Check valve

A valve that only allows flow in one direction. It is often implemented as a security measure in different parts of a vacuum system.

Centralized vacuum system

A centralized vacuum system means that a central vacuum source is used to generate the vacuum for two or more suction cups.

Cycle time

In vacuum handling and other workflows involving repetitive processes, cycle time refers to the time taken to complete one cycle.

Compression ratio

The ratio between the outlet and the inlet pressure of a gas in e.g. a vacuum pump.

D

Decentralized vacuum system

In a decentralized vacuum system, a vacuum is generated directly at each individual suction cup, as opposed to using a centralized vacuum source for several suction cups.

Dry vacuum pump

A vacuum pump that does not use oil or any other fluid in the pumping chamber when creating a vacuum.

E

Evacuation time

The time taken to evacuate a specific volume of space to achieve a required level of vacuum.

F

Flow rate

The amount of air that passes through a vacuum system within a specific time frame. It may be expressed in volume flow terms such as CFM (cubic feet per minute).

Flow resistance

Flow resistance refers to friction occurring in a vacuum system, which affects the pressure and rate of air flow.

Friction coefficient

The friction coefficient refers to the relationship between the force exerted by friction between two objects and the contact force holding them together.

G

Gauge pressure

The pressure measured with the zero-point referenced against ambient pressure. The gauge pressure unit is PSIG (pounds per square inch gauge).

H

Holding force

Holding force is the force applied by a suction cup to grip a workpiece. It is determined by the negative (vacuum) pressure and the effective suction area of the cup.

High vacuum

A vacuum range between 10^-3 and 10^-6 Torr.

I

Inches of mercury

A common scale used to measure vacuum pressures, designated inHg.

Inner volume

The inner volume is the volume of the body that must be evacuated during the suction procedure. This volume has an effect on evacuation time.

Inlet pressure

In a vacuum system, inlet pressure refers to the total pressure at the vacuum pump’s inlet.

Isolation valve

When a vacuum pump is turned off, an isolation valve seals off a vacuum system from the pump.

L

Low vacuum

A vacuum range also known as rough vacuum or coarse vacuum. It describes any level of vacuum below atmospheric pressure down to 25 Torr. Vacuum lifting systems operate in this range.

Leak detector

An instrument used to identify leaks in a vacuum system.

M

McLeod gauge

A mercury-based vacuum gauge used to measure the pressure in a vacuum system.

Mean free path

Mean free path refers to the average distance that a gas molecule can travel before it collides with another gas molecule. It is dependent on the density of the gas and the sizes of the molecules.

Medium vacuum

A vacuum range with an absolute pressure between 25 to 1×10^-3 Torr.

Micron

A micron is both a unit of measurement (one millionth of a meter) and a unit of pressure that corresponds to one thousandth of a Torr (also known as millitorr). The latter is an extremely small unit and is only used in the most demanding high vacuum range applications. In a vacuum lifting system, micron more commonly refers to the density of a filter, defining the size of the particles that can be removed, e.g. 10 microns. For comparison, a HEPA filter used in a vacuum cleaner may have a density of 0.3 micron.

Millimeter of mercury

A common unit used for measuring vacuum pressure, designated mmHg.

N

Negative pressure

​A level of pressure below that of the surrounding environment. Any significant negative pressure is considered a vacuum.

Nominal flow

Nominal flow describes the maximum gas flow through a tube of a specific diameter.

Normal force

As opposed to shear force, which acts tangentially to a surface, normal force is the force acting perpendicular to a surface.

O

Overpressure resistance

Overpressure resistance indicates the maximum pressure that a specific part of a vacuum system can withstand.

P

Partial pressure

In a mixture of gases such as air, partial pressure is the pressure exerted by an individual gas such as nitrogen or oxygen.

Pirani gauge

The Pirani gauge is a thermal conductivity gauge used for measuring pressures in vacuum systems.

Pressure

The force that a gas exerts per area unit.

Pressure differential

Expresses the difference between the pressure on a component’s inlet side and the pressure on its discharge side.

Pumping speed

The volume of gas that a vacuum pump is able to remove from a system per unit of time.

R

Reference pressure

A specific pressure referred to by a sensor to determine the pressure in a system.

Relative pressure

In contrast to absolute pressure, relative pressure is the pressure value in relation to the prevailing ambient pressure.

S

Shear force

As opposed to normal force, which acts perpendicular to a surface, shear force is the force acting perpendicular to a surface.

Suction rate

Suction rate (or suction force) is a value that indicates the volume that can be evacuated by a vacuum generator per unit of time.

V

Vacuum

A level of pressure that is significantly lower compared to atmospheric pressure.

Vacuum system

The complete set of components that make up, for example, a specific vacuum lifting solution.

Ventilation time

Refers to the time it takes to dissipate the vacuum from a system.