single vs two stage air compressor
By Published On: October 31, 2024Views: 376

Single vs two stage air compressor

Single-stage and two-stage air compressors refer to the number of times the air compressor compresses the air to the desired pressure. Each time the air is compressed, it is a stage. There are also multi-stage air compressors that have multiple compression progress (such as the common multi-stage centrifugal air compressor). The more stages a compressor has, the closer it to isothermal compression, and the more efficient and energy saving it is.

KOA Series centrifugal air compressor applications

What is single stage air compressor?

In a single-stage compressor, air is compressed only once, sucking air from the external environment and compressing it to the design pressure, and then processing it through cooling and exhaust. Compared with two-stage compression, single-stage air compressors have fewer parts, lower cost, easier to use, and lower maintenance costs.

What is single stage air compressor

(Single-stage rotary screw compressor air end )

And because single-stage compressor is small in size, light in weight, and occupies less space, it is often manufactured as a mobile air compressor. It is very suitable for light industrial and commercial applications.

However, the compression ratio of single-stage air compressors is relatively low, and the temperature is high, which is easy to cause machine wear and damage.

What is two stage air compressor

Two-stage air compressor compresses air in two stages. First, primary compression is performed in the first compression area to compress the air to an intermediate pressure, and then the air enters the second compression area for secondary compression to compress the air to the final design pressure.

During the compression process of this two-stage compressor, the intermediate cooling process can improve efficiency, reduce temperature and save energy.

single stage air end vs two stage air end

(Single stage air end vs Two stage air end)

The main advantage of two-stage compression is that it can provide a higher compression ratio and higher power output, which is conducive to extending the service life of the air compressor. However, the cost of two-stage compression air compressor is higher, and the maintenance and servicing costs are also higher.

Difference between single vs two stage air compressor

Single stage air compressor vs two stage air compressor, the main difference between the two lies in the compression process, pressure range, work efficiency and applicable scenarios.

Working principle

Single-stage air compressor: In a single-stage compressor, the compression process of air begins by sucking it into the cylinder. The piston compresses the captured air to a pressure of about 120psi, after which the compressed air is pushed into the air tank for subsequent use.

Two-stage air compressor: It includes two compression cylinders, the high-pressure stage and the low-pressure stage. The low-pressure stage compresses the gas first, undergoes intermediate cooling in the middle, and then sends it to the high-pressure stage to be compressed again to the target pressure.

two stage air compressor working principle

Different compression ratios

Two-stage compressors use inter-cooling to reduce the gas temperature, thereby achieving a higher compression ratio, which can compress the air to a higher pressure and produce a larger air flow. Compared with single-stage compressors, two-stage compressors have a higher compression ratio, generally 3-4, which can meet the needs of higher pressure use.

Compression process

Single-stage compressor:

A single-stage air compressor raises air from atmospheric pressure to the required working pressure through a single compression process. This process is relatively simple and is usually suitable for scenarios that require lower pressures.

Two-stage compressor:

A two-stage air compressor divides the compression process into two stages, with the gas first undergoing a first-stage compression and then entering a second-stage compression. This design can work at higher pressures, and because the compression process is spread over two stages, the compression ratio of each stage is lower, reducing energy consumption and wear.

Pressure range

Single-stage compressor:

The output pressure range of a single-stage air compressor is usually around 7~13 bar, which is suitable for some occasions where the pressure requirement is not high.

Two-stage compressor:

The output pressure range of a two-stage air compressor is higher, usually around 15~40 bar, or even higher. Such as the KT series high pressure reciprocating air compressor can reach up to 64bar. This high pressure output makes two-stage air compressors widely used in industrial fields that require high-pressure air.

KT Series20 - 40 Bar Middle Pressure PET Piston Air Compressor

(KT Series 20 – 40 Bar Middle Pressure PET Piston Air Compressor)

 

Efficiency and energy consumption

Two-stage air compressors reduce energy loss and heat generation during the compression process by reducing the compression ratio of each stage, thereby achieving isothermal compression and improving overall efficiency and reducing energy consumption. In addition, two-stage compression can better remove moisture and grease from the air, improving the quality and purity of the output air.

Transmission method

The biggest difference between single-stage and double-stage air compressors lies in their transmission principle. Single-stage compressor has only one set of air end and motor driven devices. When in operation, the motor rotates and drives the air end to rotate through belts or coupling to compress the air.

Dual-stage compressor has two sets of compressor heads. Each set of heads has a corresponding motor, which drives the rotors to rotate separately and compress the air separately. Then, the air from the two sets of air ends is combined through the same transmission components and output to the air system.

Air Compressor Transmission method

Power distribution

The power distribution of single-stage and two-stage is also different. In a single-stage compressor, all the power of the motor is transmitted by a belt to a single set of compressor heads, which complete the work of compressing the air.

In a two-stage compressor, the power of the motor will be distributed to two sets of compressor heads. Since the rotors of two sets of heads need to be driven, the corresponding motor is larger than the motor in a single-stage compressor.

Scope of application

Single-stage and double-stage compressor are also applicable to different occasions. Single-stage compressor is suitable for small, low-power, small flow air compressors, and its power is not more than 30KW. Two-stage compressor is suitable for large, high-power, large flow air compressors, the power is often above 30KW, and the air flow is also relatively large.

Other differences

In addition to the above significant differences, single-stage and two-stage compressors also differ in noise, maintenance and price. Single-stage compressor is noisy, while two-stage compressor is separate transmission, which is quieter.

In terms of maintenance, single-stage compressor is easier than two-stage compressor, because single-stage compressor has only one set of air end, which is easier to inspect and repair. In terms of price, single-stage compressors are relatively cheap, while two-stage compressors are relatively expensive.

In summary, the difference between single-stage and two-stage air compressors lies mainly in compression principle, compression ratio, performance and application. Compared with single-stage compressors, two-stage compressors have more advantages in air pressure and compression efficiency, and are suitable for the manufacture and processing of high-pressure gases.

However, in light industry or household use, single-stage compressors are sufficient to meet the needs.

Applications of single vs two-stage air compressors

Single-stage air compressor: Suitable for occasions where gas pressure is not required to be high, such as light industry, daily necessities manufacturing, some small workshops, laboratories or home use. For independent technicians, single-stage compressors are an ideal and economical choice to provide sufficient power for various handheld pneumatic tools not exceeding 100psi.

Two-stage air compressor: The air power generated by a two-stage compressor is significantly higher than that of a single-stage compressor, which makes it an ideal choice for large-scale operations, continuous applications and industrial fields that require high-pressure gas. And two-stage compressors can provide more stable air pressure, which is crucial for some pneumatic tools and equipment that require stable air pressure.

However, the cost of two-stage compressors is also relatively high, so they are more suitable for use in factories and workshops, such as manufacturing auto parts, construction, automobiles, chemicals, oil extraction, metallurgy industry, etc.

In these fields, two-stage air compressors are used to complete specific process operations, such as stamping, cutting, boilers, spraying, etc. In places with complex mechanical facilities such as auto repair shops and stamping plants, the higher capacity and powerful performance of two-stage compressors make them more suitable.

In summary, the choice between single-stage compressors and two-stage compressors depends on the specific application scenarios and needs. Single-stage compressors are suitable for low-pressure demand occasions such as small equipment, light industry and repair shops, while two-stage compressors are more suitable for large-scale, high-pressure demand applications.

Therefore, when purchasing an air compressor, you need to choose the appropriate type according to the application field and usage occasion.

Types of air compressors

There are many types of air compressors, which can be classified according to different working principles, lubrication methods, performance characteristics, uses and types.

According to the working principle, air compressors can be classified into volumetric, dynamic (speed or turbine) and semi-closed compressors; according to the lubrication method, there are oil vs oil free air compressors; according to the purpose, there are industrial air compressors, refrigerator compressors, air conditioning compressors, ship compressors, and oilfield compressors; according to the performance characteristics, there are low-noise, variable frequency and explosion-proof air compressors; according to the mobile type, there are fixed (static air compressors) and (mobile) portable air compressors.

Volumetric compressors are compressors that increase the pressure of gas by changing the volume of gas. These include piston compressors, whose compression element is a piston that reciprocates in the cylinder to compress the gas. Liquid-piston compressors use water or other liquids as pistons to compress the gas and then discharge it.

Rotary compressors achieve compression through the forced movement of rotating elements. The vane compressor is a rotary variable displacement compressor, in which the axial vanes slide on the rotors eccentric to the cylindrical cylinder, thereby compressing the gas and discharging it.

Two stage piston compressor air end

(Two stage piston compressor air end)

The twin-rotor Roots compressor is a rotary positive displacement compressor, in which the two Roots rotors mesh with each other, intercepting the gas and sending it from the air inlet to the exhaust port. There is no internal compression, and the air pressure is low. It is generally used as an air blower. The Roots blower is the earliest industrial air blower.

The screw compressor is also a rotary positive displacement compressor, in which the two rotors with helical gears mesh with each other to compress and discharge the gas. The screw compression components of the screw air compressor are manufactured in-house using the latest CNC grinders, combined with online laser technology to ensure accurate manufacturing tolerances.

The speed compressor is rotary vane compressor, which is characterized by the ability to produce continuous airflow, in which the high-speed rotating blades accelerate the gas passing through it, converting the speed energy into pressure. This conversion occurs partly on the rotating blades and partly on the fixed diffuser or return baffle.

The centrifugal compressor working principle is that a speed compressor with one or more rotating impellers (blades are usually on the side) to accelerate the gas, and the main airflow is radial. Axial compressors are also speed compressors, where the gas is accelerated by a rotor equipped with blades, and the main airflow is axial.

Mixed flow compressors are also speed compressors, and the shape of their rotors combines some characteristics of centrifugal and axial flow. Jet compressors use high-speed gas or steam jets to carry away the inhaled gas, and convert the speed of the mixed gas into pressure on the diffuser.

Permanent magnet variable frequency compressors use the stepless speed regulation characteristics of the inverter. Through the PID regulator inside the controller or inverter, they can start smoothly and can quickly adjust and respond to occasions with large fluctuations in gas consumption.

Two-stage permanent magnet variable frequency air compressors are new energy-saving products developed since 2014. They combine permanent magnet variable frequency and two-stage compression technology and have higher energy-saving efficiency.

Air compressors are widely used in manufacturing, mining, marine, medical, pneumatic conveying, sandblasting, oil fields, vehicle braking, textile, natural gas industries, such as industrial air compressor, marine air compressor, refrigerator compressor, air conditioning compressor, car wash compressor, tire inflation air compressor, CNG compressor, airbrush compressor, sandblasting and painting air compressor.