Common Terminology in the Vacuum Pump Industry

 The vacuum pump industry uses several technical terms to describe different aspects of vacuum systems. Whether you’re an engineer or a technician, familiarity with these terms is crucial for effective communication and operation. Below are some of the most frequently used terminologies:

1. Vacuum Level

The vacuum level indicates the degree of gas rarefaction in a vacuum state. It is often expressed as “high vacuum” or “low vacuum.” The international standard unit is Pascal (Pa), though Torr was previously more commonly used. One Torr equals 133.322 Pa.

2. Pumping Speed (S)

Measured in cubic meters per hour (m³/h) or liters per second (L/s), pumping speed refers to the amount of gas removed at the pump inlet within a unit of time under specific pressure and temperature conditions. The formula is: $S_p = \frac{Q}{P - P_0}$ Where:

• $Q$ is the amount of gas,
• $P$ is the current pressure,
• $P_0$ is atmospheric pressure.

3. Gas Throughput (Q)

Measured in m³/s or L/s, gas throughput refers to the gas flow rate at the pump inlet.

4. Rotational Speed (r/min)

This is the speed at which the pump rotor rotates, typically measured in revolutions per minute (RPM).

5. Ultimate Vacuum

Ultimate vacuum is the stable vacuum level achieved by a pump after thorough evacuation. Typically, after 12 hours of outgassing and another 12 hours of pumping, measurements are taken every 10 minutes during the last hour. The average of these measurements is considered the ultimate vacuum value.

6. Horowitz Coefficient

The ratio of the actual pumping speed in the vacuum pump’s gas passage area to the theoretical speed calculated based on molecular flow.

7. Conductance (C)

Conductance represents the ability of a vacuum pipeline to allow gas to flow through it. It is calculated by dividing the gas flow rate through the pipeline by the pressure difference between its ends. The unit is L/s.

8. Standard Atmospheric Pressure

This is the pressure at sea level at 0°C, approximately 101,325 Pascals (Pa). This pressure value is commonly referred to as one standard atmosphere.

9. Pressure

Pressure refers to the force exerted by gas molecules on the walls of a container per unit area, expressed in Pascals (Pa).

10. Starting Pressure

This is the pressure at which a pump can start without damage while maintaining its pumping function.

11. Foreline Pressure

The outlet pressure of a vacuum pump with an exhaust pressure lower than one atmosphere.

12. Maximum Foreline Pressure

The pressure above which the foreline pressure could damage the pump.

13. Maximum Working Pressure

The inlet pressure corresponding to the maximum pumping speed. At this pressure, the pump can operate continuously without deterioration or damage.

14. Primary Pump

The main vacuum pump in a system designed to achieve the required vacuum level for specific processes.

15. Backing Pump

A vacuum pump used to maintain the foreline pressure of another pump within its critical limits. For instance, a rotary vane or slide valve pump is often used as a backing pump for a Roots pump.

16. Roughing Pump

This pump starts the evacuation process from atmospheric pressure and reduces the system pressure to the level at which another vacuum pump can begin operation.

17. Holding Pump

When the gas flow in a vacuum system is minimal, it may not be efficient to use a backing pump. Instead, a smaller auxiliary pump, called a holding pump, is employed to sustain the primary pump’s operation. For example, a small rotary vane pump may be placed at the outlet of a diffusion pump as a holding pump.

Understanding these technical terms is essential for anyone working in the vacuum pump industry. Whether you’re selecting equipment or troubleshooting systems, a solid grasp of this terminology will improve your efficiency and communication.

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Vacuum Pump Terminology, Nuoxutech,Ultimate Vacuum, Pumping Speed, Gas Throughput, Foreline Pressure, Vacuum Systems, Roughing Pump