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.
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.
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.
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]
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.
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 |