One-Stop Technical Guide to Industrial Gas Equipment: A Comprehensive Analysis of Selection, Principles, and Maintenance for Blowers, Air Compressors, and Vacuum Pumps

1. First clarify the relationships: What are these devices?

Before diving into each device, first understand their relationships:

• Compressor It is the largest category, generally referring to all machinery that compresses gas and increases pressure.
• Blower It is a type of compressor but with a lower pressure level — outlet gauge pressure between 0.015MPa~0.2MPa is called a blower; below 0.015MPa is called a ventilator; above 0.2MPa is generally classified as a compressor.
• Air Compressor Abbreviation for "air compressor," specifically referring to compressors that compress air.
• Vacuum Pump Equipment that extracts gas from a sealed container to create a vacuum. Many blowers (such as Roots blowers) can be used in reverse as vacuum pumps.
• Roots Blower A type of blower, belonging to the positive displacement rotary blower category.
• Screw Air Compressor A type of air compressor that uses screw rotors to compress air.

2. Blower

1. What is a blower used for?

Blowers are mainly used for pneumatic conveying, ventilation, aeration, and combustion support and other scenarios. Common uses include: oxygenation in aeration tanks at wastewater treatment plants, pneumatic conveying in chemical and food industries (with oil-free discharged gas, especially suitable for applications requiring high gas purity), oxygenation in aquaculture, ventilation and blowing in smelting and power industries.

2. Working principle of blower

Blowers operate by the motor driving the impeller to rotate, drawing in air, compressing it, and then discharging it. According to the working principle, they are divided into two main types:

• Blade type (centrifugal, axial, mixed flow): Gas gains velocity and pressure under the action of the rotating impeller, and kinetic energy is converted into static pressure energy before discharge.
• Positive displacement type (such as Roots blowers): Gas is drawn in and compressed through periodic changes in volume between the rotors and the casing.

3. Blower maintenance

Daily maintenance key points:

4. Common faults and repairs of blowers

5. Blower operation procedures and safety regulations

Before starting ：

• Check if all bolts are tightened, motor and switch wiring are good
• Manually rotate the coupling to confirm flexible operation
• Close all air doors, check intake filter and pipeline for blockage
• Check if oil tank level is within normal range

During startup ：

• Closely monitor current changes; starting current must not exceed 70% of rated current
• After starting oil pump, maintain oil pressure within normal range
• Open air gate only after motor starts
• Check bearing and motor temperature (generally not exceeding 65℃)

During operation ：

• Frequently listen to internal sounds of the machine, check bearing vibration
• Monitor oil temperature, oil pressure, and the temperature of each bearing bush.
• If any abnormal vibration or noise is detected, stop the machine immediately and perform an inspection.

Downtime : First, gradually reduce the load, then disconnect the power supply and close the damper.

Safety Prohibition ：

• It is strictly prohibited to start the equipment under pressure.
• It is strictly prohibited to interrupt the supply of lubricating oil and cooling water.
• If a single start-up is unsuccessful, a third consecutive start-up is not permitted.
• Do not dismantle electrical or instrumentation equipment while the system is in operation.

III. Compressor

1. What is a compressor used for?

A compressor is a machine that compresses gas and increases its pressure, with extremely broad applications: compressed air powers pneumatic tools; compressed refrigerant is used in refrigeration and air-conditioning systems; compressed natural gas is transported; and high-pressure gases are supplied for chemical production, among other uses.

2. Working Principle of the Compressor

According to their principles, they are divided into two major categories:

• Positive-displacement compressor : Gas pressure is increased by reducing the internal volume of the compression chamber, encompassing reciprocating (piston-type) and rotary (screw-type, Roots-type, etc.) compressors.
• Velocity-type compressor : Gas is accelerated by a high-speed rotating impeller and then its kinetic energy is converted into pressure energy; this includes centrifugal, axial-flow, and other types.

IV. Vacuum Pump

1. What is a vacuum pump used for?

A vacuum pump is a device that removes gas molecules from a sealed container, thereby reducing the pressure inside and creating a vacuum. It is widely used in fields such as electronics manufacturing, food packaging, pharmaceutical production, chemical distillation, and vacuum coating.

2. Working Principle of the Vacuum Pump

Vacuum pumps are mainly divided into two categories:

• Gas transfer pump : Achieving a vacuum by continuously drawing in and expelling gas (e.g., rotary vane pumps, Roots pumps, screw pumps)
• Gas capture pump : To achieve pumping by causing gas to adsorb or condense on the inner surfaces of the pump.

Blowers—particularly Roots blowers—can be operated in reverse to function as vacuum pumps, which is a key feature of Roots blowers.

V. Air Compressor

1. What is an air compressor used for?

An air compressor, short for “air compression machine,” is specifically designed to generate compressed air. Compressed air is the “fourth major power source” in industry, used to drive pneumatic tools, control valves, perform spraying and purging operations, and supply air to instrumentation, among other applications.

2. Working Principle of the Air Compressor

Air compressors are classified according to their operating principles into positive-displacement and dynamic types. The commonly used screw air compressor is a positive-displacement rotary compressor: a pair of intermeshing male and female rotors rotates within the cylinder, causing the air volume between the rotor teeth to vary periodically and thereby completing the processes of intake, compression, and discharge.

VI. Roots Blower

1. What is a Roots blower used for?

The Roots blower is a type of positive-displacement blower. Its characteristics include low pressure (up to approximately 0.1 MPa) and a large air volume. It is commonly used in applications requiring low pressure and high flow rates, such as aeration in wastewater treatment, oxygenation in aquaculture, cement conveying, dust removal in coal mines, and the transport of chemical gases.

2. Working Principle of the Roots Blower

Gas is compressed and conveyed by two “figure‑eight”‑shaped rotor blades that perform relative motion within the cylinder. The two rotors maintain proper phase alignment via a synchronizing gear and rotate at equal speed in opposite directions inside the housing, forcibly pushing the gas from the suction side to the discharge side. Minimal clearances are maintained between the rotors and between the rotors and the housing, eliminating the need for internal lubrication.

3. Roots Blower Maintenance and Servicing

• Regularly check the lubricant level and oil quality.
• Regularly clean the air filtration system.
• When powering on, one should… First, open the vent valve. , after a 30-second startup with no abnormalities, open the outlet valve and close the vent valve.
• The mean time between failures shall be no less than 6,000 hours.

4. Common Faults of Roots Blowers

Common malfunctions include insufficient airflow, motor overload, and friction or collision between the two rotors, which can be resolved by adjusting the clearance or replacing the affected components.

VII. Screw Air Compressors

1. What is a screw air compressor used for?

Screw air compressors are a type of air compressor that uses screw rotors to compress air. They are one of the most widely used compressor types in industry today, providing a continuous and stable supply of compressed air.

2. Working Principle of Screw Air Compressors

A pair of intermeshing male and female screw rotors rotates within the cylinder, causing the air volume trapped between the rotor grooves to vary periodically as they turn, thereby sequentially completing the processes of intake, compression, and exhaust.

3. Maintenance and Servicing of Screw Air Compressors

• Perform the first maintenance after 500 operating hours or 3 months, replacing the lubricating oil, oil filter, and air filter.
• The major service interval is 1 year or 3,000 hours, during which the oil separator, engine oil, oil filter, and air filter are replaced.
• Lubricating oil has Lubrication, cooling, and sealing The three major functions: insufficient oil can lead to high operating temperatures, carbon buildup, and accelerated wear.
• Compressor Irreversible , Before the first start-up, it is essential to verify that the motor is rotating in the correct direction.

4. Common Faults of Screw Air Compressors

Common malfunctions include oil leakage at the head‑shaft seal, excessive unit temperatures, and a decline in gas production. The use of low‑quality lubricating oil or substandard wear parts can lead to blockages in the oil and gas circuits, resulting in overheating and carbon buildup.

VIII. Understanding the Differences at a Glance

In short: Pressure from low to high They are, in order: ventilation fans → blowers (including Roots blowers) → air compressors (including screw-type air compressors) → other high-pressure compressors. A Roots blower is a type of blower. ， A screw air compressor is a type of air compressor. , and Blowers and air compressors are both subsets of compressors. 。