Compressed air is air squeezed into a smaller space, increasing its pressure and storing energy.

Think of it like packing a suitcase—you press down to fit more in, and in the process, you store potential energy. When the suitcase is opened, the energy is released.

Compressed air works similarly: the energy stored in the air can be released to power tools and machinery.

Compressed air is often called the “fourth utility,” alongside electricity, gas, and water because it’s essential in many industries. Unlike the utilities we are familiar with, compressed air isn’t something you see every day, but it powers more around you than you might realize. It drives everything from factory machines and paint sprayers to the air tools used in auto repair shops.

In the compressed air industry, standardized conditions for measuring air delivery are crucial. The volume of air delivered can vary with temperature and pressure, so using consistent metrics is important for accurately evaluating compressor efficiency.

Definition and Composition

Compressed air is a fascinating blend of gases, primarily made up of nitrogen (78%) and oxygen (21%), with small amounts of other gases.

This mixture is taken from the atmosphere and squeezed into a smaller volume, resulting in higher pressure than the surrounding environment.

This process of compressing atmospheric air transforms it into a powerful tool used across various industries. From manufacturing and transportation to construction and healthcare, compressed air plays a crucial role in powering machinery, tools, and even medical devices. Its versatility and reliability make it an indispensable resource in the modern world.

How Are Air Compressors Used to Create Compressed Air?

To create compressed air, a machine called an air compressor takes in air at atmospheric pressure and squeezes it into a smaller space. This process makes the air denser and more pressurized.

Air compressors come in different types:

Positive Displacement Compressors

These include piston compressors and rotary screw compressors, which physically reduce the space air occupies, increasing its pressure.

Dynamic Compressors

These use rotating blades to speed up the air, then slow it down to increase pressure. Examples include centrifugal compressors, which are often used in large-scale industrial settings.

Once compressed, the air is stored in a tank, ready to be released when needed, like a spring that has been tightly wound. When the air is released, it can power various tools and equipment, much like electricity powers a light bulb.

Air Compressor Basics

An air compressor is a remarkable device designed to compress air into a smaller volume, thereby increasing its pressure. There are several types of air compressors, each with its unique mechanism.

Positive displacement compressors, such as piston and rotary screw compressors, work by physically reducing the space the air occupies, thus increasing its pressure.

On the other hand, dynamic compressors, including centrifugal and axial compressors, use rotating blades to accelerate the air and then slow it down to boost the pressure.

Rotary compressors, which use a rotor to compress air, are another common type. Each type of air compressor has its specific applications, making them versatile tools in various industries.

Properties of Compressed Air

Compressed air boasts several properties that make it incredibly useful for a wide range of applications.

One of its standout features is its flexibility and versatility as a medium for storing and transmitting energy. Compared to other energy storage methods like batteries and steam, compressed air is relatively safe.

The temperature of compressed air is directly linked to the mean kinetic energy of its molecules, meaning that compressing air increases its temperature due to the “heat of compression” phenomenon. This unique property allows compressed air to be used in diverse settings, from powering pneumatic tools to driving complex industrial processes.

Air Pressure and Storage

Storing compressed air involves keeping it in tanks or cylinders under pressure. The pressure of compressed air is typically measured in units such as pounds per square inch (PSI) or kilopascals (kPa), while its volume is measured in cubic feet per minute (CFM) or liters per second (L/s).

Depending on the application, compressed air can be stored at various pressures, ranging from a few PSI to several hundred PSI. Proper storage and pressure management are crucial for ensuring the efficient and safe use of compressed air in different industrial processes and applications.

Uses of Compressed Air in Pneumatic Tools

Compressed air is incredibly versatile, with applications that range from everyday tools to complex industrial processes. Here are some of the most common uses:

• Pneumatic Tools: Many tools like drills, sanders, nail guns, and impact wrenches run on compressed air. They are lighter than electric versions and offer more power, making them popular in construction, automotive repair, and manufacturing.
• Manufacturing and Automation: In factories, compressed air is used to operate machinery, automate assembly lines, and even move parts from one stage of production to another. It helps speed up processes and ensures that machines run smoothly.
• Cleaning and Drying: Compressed air can blow away dust and debris from hard-to-reach places, making it ideal for cleaning delicate equipment and electronic components. It is also used to dry products quickly, especially in food and beverage manufacturing.
• Healthcare: In hospitals, compressed air is used in breathing apparatuses and surgical tools. It’s valued for being clean and reliable, ensuring that medical devices function accurately and safely.
• HVAC Systems: Compressed air can help control heating, ventilation, and air conditioning systems in buildings. It ensures that systems can regulate temperatures and maintain comfort in large spaces efficiently.
• Automotive Components: Compressed air plays a vital role in various automotive components, including air brakes, suspension, and airbags. Air brakes are crucial for vehicle safety systems, ensuring reliable and effective braking performance.

Benefits of Compressed Air

1. Flexibility and Versatility:

One of the biggest advantages of compressed air is its flexibility. It can power a wide range of tools and machines, from small handheld devices to large industrial equipment. Unlike electric tools, pneumatic tools (air-powered tools) are lightweight, making them easier to handle and reducing worker fatigue.

Compressed air systems can also be adapted to fit into tight or awkward spaces where electrical systems might not work well. This is especially useful in places like factories or construction sites where space is often limited.

2. Cost-Effective Operation:

While setting up a compressed air system requires an initial investment, the ongoing costs can be relatively low. Air is free, and the systems generally need less maintenance than many other power sources. They don’t have the complex wiring and circuits that electric systems do, so there’s less that can go wrong.

Additionally, compressed air systems can run multiple tools at once, making them a cost-effective solution for businesses that need to power many devices. Over time, this can lead to substantial savings, especially when paired with energy-efficient practices.

However, it’s important to consider that compressed air power can incur significant operational costs due to the electrical energy required to run compressors, which can surpass the initial purchase price within the first year when compared to hydraulic systems.

3. Safety Advantages:

Compressed air systems are often safer in environments where sparks or heat could pose a danger. Unlike electric motors, air-powered tools don’t generate sparks, which makes them ideal for use in areas with flammable gases or dust. This helps reduce the risk of fires or explosions.

Air tools also tend to run cooler, which is important in hot or confined spaces where heat buildup could be dangerous. They work well in wet or damp conditions too, where using electric tools could be hazardous.

4. Environmental Benefits:

For businesses looking to reduce their environmental impact, compressed air can be a greener option. Many air compressors now come with energy recovery systems that capture the heat produced during air compression and reuse it for other purposes, like heating water or warming buildings. This can make the entire system more energy-efficient and eco-friendly.

Safety Considerations for a Compressed Air System

While compressed air is a valuable tool, it needs to be used carefully to avoid accidents. Here’s what business owners need to know:

Heat of Compression

When air is compressed, it heats up. This heat can be harnessed for other uses, but if not managed properly, it can create hazards. For example, compressed air can become hot enough to damage hoses or other equipment if they aren’t rated for high temperatures.

Pressure Control

Compressed air can be dangerous if the pressure is too high. OSHA regulations, such as 1910.242(b), require that air used for cleaning must be below 30 psi unless specific safety measures are in place. This prevents injuries from flying debris or air entering the body.

Proper Filtration

Air compressors should have filters to remove impurities like oil, dust, and moisture from the air. This is especially important in applications like food production or healthcare, where clean air is crucial for safety. Regular maintenance ensures that filters remain effective.

Personal Protective Equipment (PPE)

When using compressed air tools, workers should wear safety glasses, gloves, and ear protection. Compressed air systems can be loud, and high-decibel noises can damage hearing over time.

Comparison to Other Power Sources

When compared to other power sources like electricity and hydraulic power, compressed air stands out for several reasons. It is a more efficient and less polluting alternative to steam engines in many applications.

In environments where equipment is prone to overloading, compressed air is safer than electricity. Pneumatic tools powered by compressed air run cooler and offer variable speed and torque, making them ideal for specific tasks.

Additionally, compressed air equipment tends to be simpler in design, with fewer parts, which makes it more rugged and long-lasting. These advantages make compressed air a preferred choice in many industrial settings, contributing to its widespread use and reliability.

Why Compressed Air Is a Smart Choice for Businesses

Investing in a compressed air system can benefit businesses in many ways:

1. Increased Productivity

With the ability to power multiple tools at once and speed up processes, compressed air helps businesses get more done in less time. This is particularly valuable in manufacturing settings where speed and efficiency are key.

2. Reduced Downtime

Properly maintained air compressors can last for years, reducing the need for frequent repairs and replacements. This means less downtime for businesses and fewer interruptions to daily operations.

3. Long-Term Savings

By fixing leaks, using appropriately sized compressors, and implementing smart monitoring systems, businesses can save up to 30% on energy costs. Solutions like SMARTLINK provide real-time data on system performance, helping businesses identify inefficiencies and optimize usage.

4. Enhanced Safety

In environments where sparks could pose a hazard, air-powered tools are a safer option. They allow businesses to operate confidently in challenging conditions, keeping workers safe and reducing liability risks.

Conclusion: Is Compressed Air Right for Your Business?

Compressed air is more than just a power source—it’s a versatile and cost-effective solution that can boost productivity, reduce costs, and enhance safety. From operating pneumatic tools to running complex industrial systems, compressed air is a reliable partner in business operations.

Whether you’re in manufacturing, construction, or automotive repair, understanding the uses, benefits, and safety considerations of compressed air can help you make informed decisions for your business. With the right setup and maintenance, compressed air systems can be a valuable asset, powering your growth for years to come.

Ready to explore how compressed air can benefit your business? Contact Air to Air Engineering today for expert advice, customized solutions, and top-quality air compressor systems. Let us help you optimize your operations and achieve new levels of efficiency.

The post What Is Compressed Air? Everything You Need to Know first appeared on Air to Air Engineering.

In this article, we will

• Review the two basic types of air compressors: positive and dynamic displacement compressor
• Review how screw air compressors work, their benefits and industrial applications
• Discuss different types of screw air compressors along with their pros and cons.
  • oil-free screw air compressors
  • lubricated screw air compressors
• Answers frequently asked questions related to screw air compressors.

What Is an Air Compressor?

The compressor automatically collects air from the environment (inlet supply) at atmospheric pressure and converts it into high-pressure air (outlet supply) through some mechanical action. The outlet compressed air is either stored or distributed to end-use applications through cylinders or piping. 

Air compressors are necessary for any manufacturing, process, or construction industry. For example, a large chunk of industrial pneumatic machinery depends on an efficient compressor one way or the other. It is a must-have tool to accomplish blowing, stirring, and sorting. Air compressors can also act as a power source for air-driven tool actuators. 

Compressed air demand of any facility can be continuous or intermittent. Continuous air demand is called the base load while varying intermittent demand represents the air demand variance. 

Powering an air compressor constitutes almost 25-30% of the energy usage by a manufacturing facility. 

Therefore, selecting and choosing a compressor that saves recurring energy costs and reduces downtime and maintenance are the prime objectives when investing in compressors for any facility.  

Types of Air Compressors

There are two basic types of air compressors positive displacement and dynamic displacement type. The positive displacement compressor (PDC) increases the pressure by reducing the fluid volume. In contrast, the dynamic displacement compressor (DDC) increases the fluid pressure by transferring the energy into the fluid by impeller action.

Centrifugal compressors achieve compression by collecting air in a high-pressure chamber while an internal impeller accelerates the air at high speed. Although DDC can achieve very high pressure but PDC are preferred and widely used because of their simplicity, efficiency, and reliability.

Principal of Positive Displacement Compressors

The volume of the intake air in all the positive displacement compressors is gradually reduced by reducing the volume of the container cavity, thereby increasing the air pressure and potential energy.

For any production facility, a large chunk (usually 15-25% or more) of energy is used to generate compressed air. Therefore, energy-efficient compressors are always in demand.

In addition, modern positive displacement compressors offer high-efficiency air compression with less downtime compared to other alternatives. PDCs have shown impressive acceptance in the process and construction industry because of their efficiency, reliability, small footprint and flexibility.

The most widely positive displacement compressors are:

1. Reciprocating air compressors
2. Rotary screw air compressors

Compressing the air by the repeated movement of a piston within the cylinder forms a reciprocating compressing action, which is suited for applications requiring an intermittent and low-throughput (less than 6000CFM) of compressed air.

For continuous air supply, centrifugal or rotary screw compressors are preferred.

Screw Air Compressors (SACs)

How does a Screw Air Compressor work?

A pair of helical screws (or rotors) intertwine to draw the air into the small cavity between the screws. The male and female rotors (screws) are turned in the opposite direction, reducing the cavity’s volume while developing pressure with each turn. As the cavity volume decrease, the trapped air starts to compress and gain potential energy. The screw length, pitch, shape of its discharge port, and rotation speed are intuitively designed to achieve a particular pressure ratio. Modern screw air compressor adapts the working pressure according to the designed pressure ratio, thus achieving high efficiency.

Furthermore, the mechanical assembly of dual rotors allows the rotary air compressors to operate without suction and discharge valves. As a result, rotary air compressors have a much more comprehensive operating range, thus making them suitable for various applications.

Why should you invest in rotary screw compressors?

1. Energy Saving & Efficiency

Energy saving is the prime objective of any industrial process; therefore, choosing screw air compressors can provide additional benefits and energy efficiency.

Moreover, unlike piston compressors, rotary screw compressors can operate for continuous and long hours without generating much heat. Therefore screw compressors are preferred since a compressor with an unlimited duty cycle is preferable in industrial processes to achieve seamless production targets.

In addition, because of low mechanical losses, rotary screw compressors are more efficient and reliable than piston compressors. The screw air compressors induce low mechanical losses and retain their capacity or throughput over an extended period, thus having a long life.

Moreover, installing the screw air compressors with variable speed drives (VSD) with a permanent magnet motor system saves even more energy costs compared to a fixed speed compressor. The flexible operation of a rotary screw compressor with VSD allows the compressor speed to slow down if the compressed air demand is reduced or vice versa. However, the compressed air flow rate remains constant, so the compressors’ running costs can be saved during reduced production demands or breaks.

2. Small Footprint & Low Noise Vibrations

Furthermore, since there are no inlet/outlet valves or impeller-based compressing, the screw air compressors are immune to vibration noise. As a result, they can operate at significantly high speeds, thus generating more compressed air for small dimensions compared to the generic piston-based compressors.

Rotary screw compressors are compact machines, and their footprint can even reduce with “full-feature” variants, having an inbuilt refrigerant dryer making the dewpoint at the outlet to +4°C.

Modern screw air compressors are available in a power range of 2-500 kW and can be customized to advanced designs, e.g., close-coupled or vertical configurations.

Another advantage of oil-less SACs is that the output compressed air contains very little oil (<3 ppm or less), which is suitable for many critical industrial processes.

3. Reliable with Minimal Maintenance Necessary

In addition, compared to other compressors, the implicit design of rotary air compressors consists of a fixed and straightforward gear drive and motor assembly. So, there is no requirement for frequent mechanical adjustments. As a result, the compressor has significantly less wear and a maintenance-free operation.

In addition, rotary air compressors are inherently safe to operators as no inspection is necessary during an extended period.

4. Instant & Continuous Compressed Air Production

Screw air compressors produce compressed air instantly by rotating the helical screws rapidly. However, rapid screw rotation raises the overall temperature of the mechanical assembly. Therefore, an internal cooling system may be required for temperature compensation.

The Advantages of Screw Air Compressors in Summary

The advantages of long life, low maintenance, and high efficiency make them an ideal choice for any industry requiring a screw air compressor in the power range of 5-500HP.

Some reasons to invest in screw air compressors for your industry are listed:

• High Efficiency
• Low vibrations and noise
• Low maintenance and high reliability
• Small size
• Long duty hours and long life (up to 80,000 hours)
• Low oil contamination in output compressed air (< 3ppm)

Rotary Screw Compressor Types

Rotary screw compressors are divided into oil-free screw air compressors (dry screw type compressors) or lubricated screw-type compressors.

The oil-free screw type rotors are synchronously driven through timing gears ensuring minimum clearance between the rotors.

On the other hand, in the lubricated-screw type, oil is the lubricant, and the primary rotor is the male rotor which drives the female rotor.

Oil Free Screw Air Compressor

The oil-free screw air compressors or dry-screw type air compressors do not need oil lubrication and have asymmetric screw movement. An external timing gear assembly is utilised to synchronise the rotors’ movement.

In addition, primary and secondary screws never come in contact with each other or their housing. Thereby eliminating friction, wear, tear, and lubrication costs. This mechanical setup results in low internal leakage, high efficiency, and reliability.

The outlet air pressure of a single-stage compression using an oil-free rotary screw compressor is limited because of the temperature difference between the inlet and outlet discharge. However, multiple-stage compression with interstage cooling can achieve a high-pressure discharge.

Applications

The common application of oil-less, oil-free or dry-type screw air compressors is in critical processes where even minor oil contamination cannot be tolerated, such as Food, Healthcare, Pharmaceuticals, and semiconductor manufacturing.

As a result, there is severe competition among rotary screw compressor manufacturers to capture the market. However, some compressor builders stand out for their reliable products. For example, the Japanese KOBELCO Air Compressor and ELGi Air Compressor are renowned compressor builders offering excellent sales service and spare parts.

Below are some of the oil-less screw air compressors available from these manufacturers.

ELGi Electric Oil Free Screw Air Compressor

The ELGi oil-free range of air compressors is efficient, reliable and cost-effective, providing class zero oil-free compressed air.

Learn more

KOBELCO Oil Free Compressors

Emeraude series are KOBELCO’s iconic line of compressors used in various industries to generate oil-free, clean compressed air.

Learn more

Oil Lubricated screw air compressor

The primary male rotor drives the secondary female rotor, and there is no requirement for timing gear assembly to synchronise both rotors. The compression chamber of the lubricated-type screw air compressor is flooded with lubricant oil, which serves many purposes, i.e., lubricating, sealing the mechanical parts, and cooling the rotors and the mechanical assembly.

As a result, the outlet discharge temperature is lower than in oil-free screw compressors, while the air leakage from the compression chamber is also minimised.

In addition, the intrinsically cooled compression in the lubricated-type SAC allows attaining significantly high pressure (15-17 bars) through single-stage compression.

However, the low efficiency, high leakage, cooling system, and lubricating oil costs are some of the disadvantages of these compressors.

Applications

Oil-lubricated screw air compressors are utilised in standard industrial processes where minor oil contamination is not an issue. They can provide high flow throughput (CFM) with a 100% duty cycle.

Some of its applications are Pneumatic conveyor belts, paint production lines, and robotic and CNC manufacturing. KOBELCO Air Compressor and ELGi Air Compressor also build Oil lubricated screw compressors.

The following figures and the links to their products are given below.

ELGi Electric Lubricated Screw Air Compressor

ELGi’s EN Series screw air compressors are perfect for businesses that need compact and low-maintenance machines with small footprints.

Learn more

ELGi Electric Oil Free Screw Air Compressor

Known for their high quality and reliable compressors, the new ELGi EG Series is designed with ease of maintenance in mind.

Learn more

KOBELCO Oil Injected Compressors

Kobelion is an energy-saving KOBELCO Oil Injected Compressor designed for a wide range of general manufacturing applications.

Learn more

How to choose your rotary screw compressor?

Making a prudent choice when selecting a compressor can be rewarding in terms of saving recurring energy and maintenance costs.

Positive displacement compressor choices are

• piston-based compressor
• oil-lubricated rotary screw compressor
• oil-less rotary screw compressor

The compressor selection primarily depends upon outlet airflow (cubic feet per minute), air pressure (bar), and air quality. Next, the efficiency, duty cycle, noise/vibrations, and cost are compared.

Finally, the operating environment (outdoor, indoor, offshore), ambient conditions, storage, and piping system are also important considerations.

Repair, maintenance and servicing of the screw compressor

Schedule compressor maintenance provides many long and short-term benefits. As a rule of thumb, the scheduled inspection and maintenance is after six months or 1000 hours of operation.

1. An unplanned compressor downtime is undesirable for any industry. However, preventive and scheduled maintenance significantly reduces downtime and saves repair and spare parts costs.
2. Efficiency is maintained over a more extended period for the compressors which receive scheduled servicing. For example, only a reduction few PSI of output pressure of a compressor raises overall energy consumption by 1%.
3. Longer life is guaranteed for a well-maintained rotary air compressor.
4. Regular maintenance of the rotary compressors enhances personnel, equipment, and facility safety.

Contact our specialist today to conduct your regular preventive maintenance.

Rental of Screw Air Compressors

Operating a screw air compressor for a limited duration for a one-time project can be costly. Therefore, Air to Air Engineering offers a rental service for the screw air compressor you require at a nominal cost. In addition, we provide excellent inspection, repair, and maintenance services. Some of the maintenance tasks for your rotary screw compressor can be delegated to us, which include:

• Inspection and repair of drive train assembly and belts.
• Control system inspection and adjustment.
• Oil inspection, recommendation, and replacement.
• Repairing inlet/outlet valves, filters, and piping.
• Servicing and lubricating motors
• Repairing and servicing the cooling system.
• Draining water and oil.

Eager to know more about our air compressor rental services? Contact us today, and our dedicated specialist will follow up with you as soon as possible.

FAQs

1. What is a screw-type air compressor?

Screw air compressors produce compressed air by the rotation of two helical screws rotating in opposite directions. The ambient air is trapped in the cavity between the rotors; as the rotors turn in the opposite direction, the volume of the cavity reduces to compress the trapped air.

2. What is a screw compressor used for?

Screw air compressors are essential industrial equipment. Depending on the application requirement, oil-lubricated and oil-less screw air compressors are used in process manufacturing, chemical plants, pharmaceutical, food, and semiconductor industries.

3. How does a screw-type air compressor work?

A pair of helical screws (male and female) are assembled to form a cavity. The volume of the cavity gradually reduces when the screws are turned in the opposite direction, thus compressing the air trapped in the cavity.

4. Should I choose a piston (reciprocating) compressor or a screw compressor?

Piston compressors provide higher air pressure ( >150psi ) with an intermittent duty cycle, while rotary screw compressors are recommended for applications operating under 150psi with a continuous duty cycle. Oil-less rotary screw air compressors are the only choice for critical pharmaceutical, food, and healthcare processes. Industrial mixing plants, robotics manufacturing, semiconductors, and CNC machines utilise screw air compressors extensively. In addition, screw air compressors are suitable for industrial tooling like blowing, stirring, cleaning, and sorting.

5. Do screw compressors need a tank?

Rotary screw compressors are versatile equipment capable of operating without a storage tank. The tankless option is preferred when the compressor operates in small bursts without wasting time in tank filling. Compared to piston compressors, the tankless operation of screw air compressors has a significant time and cost-saving advantage. However, the end user always has an option either to go tankless or with a tank.

The post Rotary Screw Air Compressor: an Extensive Guide first appeared on Air to Air Engineering.