Vacuum Pump / Blower Basics

What is Vacuum?

Under the Japan Industrial Standard (JIS), a vacuum is defined as "a condition of space filled with a gas such that it is below normal atmospheric pressure" (JIS Z 8261-1), and there are 4 classifications of vacuum ranges.

Vacuum Pressure Range Name
100kPa to 100Pa (105Pa to 102Pa) Low Vacuum
100Pa to 0.1Pa (102Pa to 10-1Pa) Medium Vacuum
0.1Pa to 10µPa (10-1Pa to 10-5Pa) High Vacuum
10µPa or under (10-5Pa or under) Ultra-High Vacuum

The pressures in the chart above are such that a perfect vacuum (a space of complete vacuum that does not contain even a single atom) is considered to have a value of 0 (zero).
Also, while not established with JIS, 10-9 and lower degrees of vacuum are referred to as "extreme high vacuum", and has been established as a technical term.

What is a Blower?

According to JIS B 0142, compressed air is defined as "air which has been compressed for use as a power transmission medium", and according to JIS B 0132, a compressor and a blower are defined as follows.

Term Definition
Compressor A machine that discharges gas by means of the rotational movement of an impeller or rotor, or the reciprocating movement of a piston.
Blower Among compressors, the effective discharge pressure is 200 kPa or less.

Among compressors, a blower is considered to be a device which can produce low pressure air of 200 kPa (0.2 MPa) or lower.

Types of Vacuum Pumps

There are various types of vacuum pumps such as dry pumps, oil rotary pumps, liquid ring pumps, and ejector pumps.
Among these, dry pumps are a type that do not use oil or sealing liquid along the gas transfer course, and include pumping methods used in rotary vane pumps, Roots pumps, and screw pumps, and others.

Types of Dry Pumps

Positive Displacement Type Rotating Type Rotary Vane Pump
Claw Pump
Multi-Stage Roots Pump
Scroll Pump
Screw Pump
Reciprocating Type Diaphragm Pump
Piston Pump
Bellows Pump
Momentum Transfer Type Mechanically Driven Type Side Channel Blower
Turbo Vacuum Pump

Rotary Vane Pump

This type of pump operates by carbon plates, called a "vanes" (plate-like blades) which slide out due to centrifugal force and rake out air.

Rotary Vane Pump

Claw Pump

A pair of claw rotors, each with a claw-like protrusion, are rotated in opposing directions at a constant speed without making direct contact, thus compressing intake air and then blowing it out.

Claw Pump

Multi-Stage Roots Pump

This is a multi-stage pump where a series of rotors with figure-eight cross sections rotate contactlessly in opposing directions at a uniform speed.

Multi-Stage Roots Pump

Scroll Pump

A pump that operates with two identically spiral shaped scrolls, one fixed, and the other being rotated inside the fixed one.

Screw Pump

A single-stage pump where a pair of screw-shaped rotors are contactlessly rotated in opposite directions at a constant speed in order to draw in air, which is compressed and then blown out.

Vacuum Units (Gauge Pressure and Absolute Pressure)

Vacuum units are given in absolute pressure or gauge pressure. Absolute pressure is zero-referenced to a perfect vacuum, and gauge pressure is zero-referenced to atmospheric pressure. Note that these are relative pressures (※). ORION uses gauge pressure referenced to atmospheric pressure.
※ Conversion formula: Absolute Pressure [kPa] ≒ 101.3 [kPa] - Gauge Pressure [kPa]

Gauge Pressure and Absolute Pressure

The unit specified for pressure under the International System of Units (SI) is the Pascal (Pa). Under the New Measurements Act, units of mmHg and Torr are not to be used for commercial transactions. A units comparison chart is shown below for reference. Here is a conversion chart.

Pressure Unit Comparison: Absolute Pressure
Pressure Unit Comparison: Absolute Pressure
Pressure Unit Comparison: Gauge Pressure
Pressure Unit Comparison: Gauge Pressure

Units Conversion Chart

Conversion to Degree of Vacuum (Gauge Pressure)

Unit of Vacuum Degree of Vacuum (Gauge Pressure)
From To kPa mmHg mbar
1kPa 1 7.5 10
1mmHg 0.1333 1 1.333
1mbar 0.1 0.75 1

Conversion to Absolute Pressure

Unit of Vacuum Absolute Pressure
From To kPa[abs] Torr atm mbar[abs]
1kPa[abs] 1 7.5 9.87×10-3 10
1Torr 0.1333 1 1.316×10-3 1.333
1atm 1.013×102 760 1 1.013×103
1mbar[abs] 0.1 0.75 9.87×10-4 1

Conversion to Exhaust Pressure (Gauge Pressure)

Unit of Pressure Exhaust Pressure (Gauge Pressure)
From To kPa kgf/cm2 psi mbar
1kPa 1 1.02×10-2 1.45×10-1 10
1kgf/cm2 98.07 1 14.223 9.807×102
1psi(lb/in) 6.89 7.031×10-2 1 68.9
1mbar 0.1 1.02×10-3 1.45×10-2 1

Flow Rate Conversion

Unit of Flow Rate
From To cfm m3/h L/min L/s m3/s
1cfm(ft3/min) 1 1.6992 28.32 0.472 4.72×10-4
1m3/h 0.589 1 16.67 0.278 2.78×10-4
1L/min 0.0353 0.06 1 0.0167 1.67×10-5
1L/s 2.119 3.6 60 1 10-3
1m3/s 2119 3600 60000 1000 1