How Does an Air Compressor Work?

How Does an Air Compressor Work

Many people use air pressure equipment without knowing how they work. Normally, air compressors run as stand-alone installations or complement other tools. They have a range of uses at home and in industrial workspaces. Air compressors may fail to deliver high performance with poor maintenance and handling. Also, poor installation of air compressors could affect their efficiency. 

Let’s tell you how this mechanical equipment works.

What Are Air Compressors

Air compressors are mechanical devices that take air from the atmosphere, pressurizes, and release the kinetic energy. They are an important home workshop and garage equipment. In factories and workshops, air compressors perform pneumatic operations.

One of the characteristic features of industrial air compressors is its large components. Wheels, belts, air tanks, gauges, pumps, and hoses are some important working parts of the compressor unit.

However, air compressor comes with different designs like the cordless and quick-connect hose types.

They might have similar working principles, different mechanisms, shapes, and sizes. As power sources for air tools, these mechanical devices offer pressure for electricity too.

How To Run Air Compressors?

Usually, DIYers don’t read the operating manuals of new air compressors. A quick way of checking the specifications of this mechanical device is with their data plates.

In this guide, we shall discuss other kinds of stuff that affect the air compressor’s efficiency.

The reciprocating piston technology is a basic working principle of an air compressor type. You may see a range of compressor models on the market.

Since they are mechanical equipment that relies on motors, expect them to generate compressed air with pressure. These motors might not run quietly because of their moving parts.

Types Of Air Compressors

Despite their complex mechanisms, most air compressors are simple to operate. It’s important to know the components of every unit in an air compressor. The type of air compressor that you need depends on the capacity and purpose.

Classification According To Power Source

Another classification of air compressors is according to their power source. Gas and diesel-powered air compressors pollute the environment more than electric versions.

Also, some gas-powered air compressor models have hybrid internal combustion mechanisms. It means that operators can use either gas or diesel with one air compressor machine.

Classification According To Pressure Output

Generally, there are three classifications of compressors according to pressure output.

The Low-Pressure Air Compressors (LPACs) operate with a maximum discharge pressure of 150 PSI. Some models of PORTER-CABLE air compressors with electric motors operate at 150 PSI (max).

You’ll see medium-pressure compressors with discharge pressures between 151 to 1,000 PSI. High-Pressure Air Compressors have discharge pressures of above 1,000 PSI.

Classification According To Air Displacement

Apart from pressure output, the displacement of air is a classification of compressor systems. During operations, the piston rods of air-displacement compressors are in constant motion.

Without changing positions, there will not be enough mechanical force to store, compress, and produce air pressures. There are two methods of displacing air with this mechanical equipment.

There are two methods of displacing air with this mechanical equipment :

  1. Positive Displacement
  2. Dynamic Displacement

Positive Displacement

In compressors with positive-displacement mechanisms, air goes into a chamber (that closes and opens) with force. The volume of the air reduces for compression to occur. The system has to attain its maximum pressure.

Then, the valves open and allows air from the compression chamber to enter into the storage tank with force. Examples of positive-displacement compressors include rotary-screw, piston, vane, and scroll types.

Generally, these types compress and store air with a positive-displacement internal mechanism.

YouTube video

Piston Air Compressors

As positive-displacement compression systems, their basic working principle is to pump air into their chambers. These types use piston rods that perform both downward and upward strokes.

Also, their internal mechanisms consist of (inlet and outlet) valves that guide air through their chambers.

These piston rods work like the types in automobile engines. With downward strokes, air flows into the chamber and out (in the storage tank) when they make upward strokes.

Also, there are two types of piston compressors – single-stage and two-stage models. Normally, two-stage compressors have more efficiency than single-stage types. Check the ratings on the data plate to know the capacity of any type of piston air compressor.

Differences Between Single And Two-Stage Compressors

Air Compressor How it Works

Both single-stage and two-stage models complete full compression cycles (stroke). With a single stroke, the crankshaft makes full rotation that moves the piston rod. Most single-stage models run quietly. Low-noise models like the DEWALT 6-gallon air compressor have multiple pistons that make lower RPMs (revs per minute) rotations.

In the two-stage air compressor, one stroke triggers a piston to compress. Then, the second stroke forces air with high pressure into a cylinder for the second stroke. The completion of both strokes increases the air pressure inside the tank.

Rotary-Screw Compressors

As positive-displacement compression systems, they have dual-helical screws designs. It’s this mechanism that helps to guide air into their chamber. When these screws turn, they reduce the volume of air inside the chamber.

Vane Compressors

As positive-displacement compression systems, they deliver specific volumes of air at high pressures. These types of piston air compressors have built-in rotors with variable arrangements of blades.

With these blades, the unit can guide air into the chamber before they compress the volume.

Dynamic Displacement

Dynamic displacement air compressors have slight variations from positive-displacement systems. These types force air into chambers with rotating blades and impellers.

Since the blades are in constant motion, they provide energy from that build air pressure.

Some examples of non-positive displacement types are centrifugal and axial compressors.

The advantage of operating this air compression system is its quick output of compressed air. Also, non-positive displacement compressors offer high volumes of air.

Many automobiles with turbochargers use this technology. However, their designs are useful in both commercial and industrial applications.

Usually, these applications require constant pressure and large volumes of air flow-rates.Regardless of the reciprocating piston’s variation, they work with the following components. Apart from the valve head, they have connecting rods, pistons, crankshafts, eccentric rings, and cylinders. However, your air compressor power is a factor of a motor’s horsepower.

How To Reduce Pressure Drops In Air Compressor Systems

How Air Compressor Work

The air compressor unit doesn’t work for a very long period without developing some common problems. During work, operators don’t want to experience any decrease in performance because of excessive pressure drops.

Usually, drops in pressure output are basic problems, but they might be expensive to fix. One of the ways of troubleshooting or avoiding air compressor pressure drop is by reading this article further.

Couplings, Hoses And Tube Leaks

Normally, pneumatic machines use hoses, even handy air tools. When couplings are loose, it’s the same effect as hoses leaks. There will be gradual drops of air pressure. Also, inlet points of applications could have rusty metal tubes. It’s another chance for pressure drops.

When metals degrade from corrosion, they have weak and brittle structures that are prone to cracks. However, operators should replace defective hoses, metal tubes, valves, inlet, and outlet valves.

Faulty Nozzles

Usually, nozzles for high-pressure applications influence the performance of pneumatic systems. There will be pressure drop when air fittings around nozzles allow leaks. Inspect pressure gauges often to see compression output levels.

Air Filters

While it’s important to filter impurities from atmospheric air, the environment with pollutants degrades air filters. Also, pressure drops when solid or liquid particles in filters reduce the flow of air between pressurization chambers.

To avoid these conditions, change your air filters according to the maintenance checklist recommendations.

To avoid these conditions, change your air filters according to the maintenance checklist recommendations.

Lubricators

When lubricators of rotary compressors don’t work properly, there will be a drop in an air compressor’s efficiency. The drop in pressure strains the pump too. A low fluid level might cause abnormal noise and vibration. Inspect pressure gauges to see compressed air output levels.

After every eight hours of running the air compressor, monitor the indicators, and check for fluid leaks. In extreme conditions of faulty lubricators, the technician might need to open the air/fluid reservoir valve and drain water.

Connectors

Ensure tight connections elbows and piping tees. Sometimes loose connectors allow the escape of air when they are not tight. Buy modern products like the Campbell Hausfeld portable air compressors. They come with small connectors with sealed joints that are leak-proof. Don’t forget to change these connectors if you experience air leaks from them.

The Effects Of Lubrication In Air Compressors

Lubrication increases the lifespan of air compressors. Without oil, piston rods will generate much heat and noise during operations. In worse cases, insufficient lubrication affects eccentric rings, bearings, and cylinders. This condition of low lubrication can trigger some knocking signs. Additionally, it might damages the engine blocks of air compressor pumps.

Oil-Lubricated Pumps

Air compressors that depend on lubrication need piston rods to move with less friction. Without oil, these piston compressors will have low efficiency and experience wear. Light-duty compressors with coated pistons run on less oil.

When there’s oil flooding, the cylinder of lubricated pumps will seep oil into compression tanks. Also, airstreams with oil reduce efficiency and cause strain on the motor after a long period. 

Some common signs of this condition include oil splashes on the bearings and walls of the chamber. Install high-quality air-line filters and oil separator parts in your compressor.

Oil-Free Pumps

Oil-free pump bearings work efficiently with lasting lubrication. So, they need less maintenance and oil changes than oil-lubricated pumps. Also, it’s rare to experience noisy movements of components inside oil-free compressor pumps.

Pros Of Using Oil-Free Pumps:

  • Their design promotes less consumption of oil that makes them cost-effective models.
  • There’s no risk with their pistons undergoing wear and tear from friction.
  • They are durable without signs of corrosive internal parts.
  • Unlike oil-lubricated pumps that require daily checks, this air compressor runs without any risk of low lubricant levels.

Cons Of Using Oil-Free Pumps:

  • Oil-free compressors generate heat faster than pump models that run on lubricants.
  • During heavy-duty tasks, they become noisy within short periods of operations.

Specification And Air Compressor Power Ratings

The Cubic-Feet Per Minute (CFM) Factor

The CFM is a standard for measuring the volume of air inflows in compression systems. Usually, it’s the speed of atmospheric pressure into compressors that determines the CFM. Also, humidity and temperature of atmospheric air affect cubic-feet per minute values.

Most nail gun models use 3 CFM of air, and high-volume (high pressure) spray-painting guns need at least 14 CFM. While calculating SCFM values, we consider the CFM to be 68 degrees Fahrenheit (at sea level) with 36% relative humidity. 

Consider the air volume for your applications (pneumatic tools) before buying an air compressor.

The PSI Factor

The PSI(Pounds per Square Inch) is a standard unit for measuring air pressure. You might see data sheets of air compressors with 3 CFM and 90 PSI ratings. According to Bernoulli’s principle; when air volumes (in standard cubic feet per minute SCFM) increase, it reduces the PSI of compression systems.

Air Regulator

Air regulators are the hardware of air compressors. They control the flow rate of air that goes and enters the machine. Normally, air regulators have two gauges and one knob. In most air compressor models, the operator can monitor the tank’s internal pressure and airflow pressure (in PSI) from the regulator.

Energy Efficient Air Compressors Are Ideal

More efficient oil-free compressors use variable-speed drives. This innovative operation of air compressors works with the principles of fluid power technology. Operators and owners of air compressors with energy-efficient electric motors can save costs from electricity consumption.

Additionally, sustainable air compression operations produce low or zero CO2 emissions.

Conclusion

It’s important to understand the basics of how air compressors work before installing them. Mechanical breakdowns are inevitable with pneumatic equipment, but proper maintenance culture can increase the efficiency of machines.

After reading this comprehensive guide, we expect both DIYers and operators to make good buying decisions. However, air compressors with system safety-shutdown features are more reliable.

Leave a Reply