Compressed air can be damaging to applications that require moisture-free air. Atmospheric air that enters an air compressor intake contains water vapor.
While in the air compressor, heat from compression and pressurization forces water vapor to condense into liquid droplets.
These droplets travel downstream and can ruin your products, air tools, cylinders, and air motors.
Refrigerated air dryers take the moisture-laden air from the air compressor discharge and lower the temperature condensing the water vapor to water and separating it from the air before it goes downstream damaging product and equipment.
How Does a Refrigerated Air Dryer Work?
Compressed air enters the air dryer at a temperature of around 100F. The air enters an air to air heat exchanger.
In this heat exchanger, the incoming air is pre-cooled by the outgoing cold air. The air then enters a refrigerant to air heat exchanger which cools the air to around 35F.
At this lower temperature, the moisture in the air is condensed and separated out of the air and is expelled from the unit.
Lastly, the air travels through the previously mentioned air to air heat exchanger allowing the incoming warm air to reheat the colder air leaving the air dryer.
The compressed air leaving the dryer has a pressure dew point between 35°F to 50°F.
2 Types of Refrigerated Air Dryers
Non-cycling refrigerated dryers
Non-cycling refrigerated air dryers operate with the refrigeration compressor running continuously, regardless of the inlet load.
Minimal energy savings is realized from 100% down to 0% inlet air load.
Cycling refrigerated air dryers automatically cycle the refrigeration compressor on and off in response to inlet load conditions as the inlet air load is reduced the refrigeration compressor cycles off, providing energy savings.
This is done through some type of thermal mass that holds the temperature once the air compressor cycles off.
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Rotary screw air compressors controlled by VSDs (variable speed drives) are one of the best energy efficient industrial innovation introduced in the past few years.
The style of air compressor control can reduce energy wasted by compressors running in the unloaded condition exponentially.
Variable speed air compressors are ideal for plants that have fluctuating demand.
Some examples of this demand include Single shift seasonal type businesses that have higher production levels for a couple of months out of the year, or 24/7 operations, that have varying demands between shifts.
Variable Speed Air Compressor Benefits
- Reduced energy consumption
- Quieter than a fixed speed when running at a lower RPM
- Consistent plant pressure increased component lifetime
- Low inrush current during motor starts
- May qualify for energy incentives
Single State vs. Two Stage Variable Speed Air Compressors
The main difference between single and two-stage air compressors are the number of compression stages.
Single stage air compressors compress air from atmospheric pressure to operating pressure in one stage.
A two-stage compressor uses two stages to compress the air.
The first-stage compresses the air to around 30 psig after which it is cooled before entering the second stage.
In the second stage, the air is compressed from 30 psig to operating pressure usually around 100 or 125 psig. This allows for the compressor to reach operating pressure more efficient
- 100 horsepower single stage delivers 436 CFM @ 125 psig
- 100 horsepower two-stage delivers 513 CFM @ 125 psig
Variable Speed Compressors at Energy Machinery
At Energy Machinery, we offer 24-hour field service and certified technicians are available with for troubleshooting and repairs, turnkey instructions, and planned maintenance programs.
We are an authorized warranty repair center for Gardner Denver, Champion, and Cooper Cameron compressors.
Take a look at our variable speed air compressors below. If you need help finding the right one for your business, contact us today and a representative will reach out to you quickly!
Air compressors, like many other types of mechanical equipment, require adequate lubrication to ensure maximum longevity and optimum performance. The piston, in particular, needs to be able to draw and compress air with minimum frictional resistance. In this regard, air compressors are available in two primary configurations: oil vs oil free air compressor systems.
In oil-lubricated compressors, oil is used to reduce the friction between the piston and the walls of the piston chamber. Oil may even be splashed onto the walls and bearings of the cylinder by means of an oil bath. This type of compressor is also referred to as oil-flooded.
On the other hand, oil-free compressors, as their name suggests, do not require lubrication oil. Instead, the piston is pre-lubricated with a Teflon (PTFE) coating. Teflon has one of the lowest coefficients of friction among any solid due to its layered structure, which possesses relatively weak intermolecular bonding forces. These layers easily slide past each other with minimal effort, significantly reducing the friction between the coated elements.
While many compressors in use today are oil-lubricated, oil-free compressors are quickly gaining popularity among various industries. Oil-free compressors are less expensive and capable of achieving the same level of performance as their oil-lubricated counterparts in most applications, making them ideal for myriad industrial purposes.
However in the case of oil vs oil free air compressor machines, which one does your business need?
Oil Vs Oil Free Air Compressor: Which One Is Best for You?
One of the defining features of oil-free compressors is the absence of interaction between the lubricating oil and the compressed air. In oil-lubricated compressors, the air inevitably comes into contact with the oil, introducing a degree of contamination.
Oil droplets, vapors, mist, or liquids can make their way into the output compressed air. This problem is eliminated in oil-free compressors, leading to a better quality compressed air supply. This is especially valuable in applications where air quality is paramount, such as in dentistry or cleanroom compressors.
Oil-free compressors are also significantly lighter than oil-lubricated compressors, making them ideal for commercial applications that require portability, such as tire inflation, jackhammering, medical air supplies, and roadside assistance pneumatic tools.
Oiled compressors, on the other hand, are bulkier, heavier, and often require mounting. This makes them better suited for situations where the equipment does not require frequent relocation.
How to Maintain an Oil-Free Air Compressor
Oil-free compressors are especially renowned for their minimal maintenance requirements. The absence of lubricating oil combined with the self-lubricating nature of the Teflon coating means that the cylinder requires no further lubrication, eliminating the need for scheduled oil changes.
However, oil-free does not translate to maintenance-free. These pumps must still undergo routine maintenance to ensure safe and efficient compressor operation and optimal service life. Oil-free air compressor maintenance usually consists of checking the following components:
When inspecting the compressor safety valve, first ensure that the compressor is plugged in and allowed to reach its shut-off pressure. Next, remove the safety valve ring to release the pressure from the tank and observe the valve. If the air is not discharged, or if the valve does not close automatically, then the valve may need to be replaced.
Condensation can cause water droplets to build up inside the tank. Ensure that that tank is adequately drained after each use by locating the drain valve and allowing the tank to drain completely.
Be sure to inspect the filter for dirt build-up and wear. Depending on the compressor model, the location, and type of filter (paper, felt, or foam) may vary. Paper or felt filters with significant contamination buildup need to be replaced. Foam filters can be cleaned with soap and water and replaced upon drying. All damaged or worn filters should be replaced immediately.
Additionally, an overall inspection of the compressor should be routinely conducted. Inspect various components such as hoses, valves, power cords, fittings, and seals for damage and signs of wear. The tank’s exterior should also be checked for rust damage, pinholes, or other weak spots. It is important to note that damaged tanks should be replaced immediately. Never attempt to weld, drill, or otherwise repair the compressor tank.
At Energy Machinery, we offer a comprehensive range of oil-free compressors for almost any industrial application. If you would like to find out more about our line of oil-free compressor solutions, feel free to view our equipment catalog or request a free quote today.
Compressors are mechanical devices used to intentionally increase the pressure of a air. They work by “squeezing” the air into a smaller volume, thereby causing a buildup of stored potential energy to be used when needed. Although there are many types of compressors, most of them generally fall under two classifications: dynamic and positive displacement.
Reciprocating compressors belong to the category of positive displacement compressors. These type of compressors operate by drawing fluid into a fixed-volume chamber via a mechanical component which physically displaces the air. Other types of positive displacement compressors include rolling piston, rotary screw, rotary vane, and diaphragm compressors.
Reciprocating Air Compressors
Reciprocating air compressors consist of a piston driven by a crankshaft enclosed within a cylinder. The typical reciprocating air compressor is also comprised of suction and discharge valves.
Compression is accomplished via a cycle of operations. First, the piston receives power from the main shaft via a rotating crankshaft. During the piston’s suction stroke, the volume within the cylinder increases while its pressure decreases. This allows the relatively higher pressure external air to open the inlet and enter the cylindrical chamber.
On the piston’s compression stroke, the volume within the cylinder decreases, raising the pressure of the collected air. This increase in pressure opens the outlet valve, causing compressed high-pressure air to flow out of the cylinder into a storage tank.
Reciprocating air compressors differ from other types of compressing mechanisms in that the flow is highly controlled. The volumetric flow rate is simply the volume of the cylindrical chamber multiplied by the piston stroke rate. In other words, the throughput of a reciprocating compressor is solely dependent on the displacement mechanism (the piston, shaft, and crankshaft). This characteristic is extremely beneficial from an automation and control standpoint.
Common Questions About Reciprocating Compressors
Can a reciprocating compressor run backward?
Generally, if the direction of a reciprocating compressor is reversed, there will be no adverse effect on the compressibility factor and air discharge/suction capacity. Lubrication, however, may become an issue. For splash-lubricated pumps, positive pressure will simply be generated at the inlet filter while a vacuum will be created at the discharge.
Can you replace a reciprocating compressor with a scroll?
A scroll compressor, also known as a scroll pump, uses two interweaving spiral-shaped vanes to compress and pressurize fluids. One scroll remains fixed, while the other orbits within it in an eccentric manner, trapping and compressing pockets of fluid between the scrolls. Generally, scroll and reciprocating compressors are interchangeable. However, specific tubing, mounting, and other modifications will need to be done by a professional.
Which compressor is better? Rotary or reciprocating?
In terms of compression efficiency, reciprocating compressors are marginally more efficient than rotary compressors. For the same amount of air, a reciprocating pump can use 5% to 10% less energy than its rotary counterpart. On the downside, reciprocating pumps can be more expensive and require more maintenance.
Reciprocating Compressors from Energy Machinery
Reciprocating compressors are simple, yet highly efficient devices. They can be found in several industries, including manufacturing, food production, agriculture, pharmaceutical, and construction.
At Energy Machinery, we provide a wide variety of reciprocating compressors for a broad range of applications. If you would like to learn more about our compressor equipment, request a quote from us today!