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Positive Displacement Compressor

Author Archives: Energy Machinery, Inc.

  1. Positive Displacement Compressor

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    Positive Displacement Compressor

    Compressors are mechanical equipment used in a wide variety of industrial and commercial settings to generate pressurized gas. They compress gas, most commonly air, by reducing its overall volume. The multiple compressor types vary based on the method of compression, power source, and capability to compress specific liquids and gases. In this blog, we’ll discuss positive displacement compressors, how they work, and what makes them different from other compressors.

    What is a Positive Displacement Compressor?

    Positive displacement compressors take in a higher volume of air per unit of time than they can release. The compressor pulls in air through a relatively larger inlet system, and the gas becomes pressurized while being forced through the smaller outlet. The mass flow rate controls this compression so that operators can compress air at different pressure levels to best suit the needs of various applications.

     

    Some different types of positive displacement blowers include:

    •   Diaphragm compressors
    •   Ionic liquid piston compressors
    •   Reciprocating compressors
    •   Rolling piston compressors
    •   Rotary screw compressors
    •   Rotary vane compressors
    •   Scroll compressors

    How Does Positive Displacement Work?

    At their simplest, positive displacement compressors draw a particular volume of gas into the compressor’s chamber and then decrease the size of that chamber. This action combines with an outlet system that forces the air to remain pressurized as it exits the compressor, resulting in elevated air pressures that operators can adjust and control. Each type of positive displacement blower uses different techniques to achieve air compression. For example, some compressors have pistons that gradually lower to decrease the available space within a chamber, and others have rotary screws that capture the gas at the inlet. 

    Some air compressors use oil as a lubricant by injecting it into the air as it’s compressed. However, most positive displacement compressors have oil-free or oil-less designs that don’t require this additional step. Oil-less air compressors don’t use oil at all, while oil-free compressors have lubricated parts that don’t contaminate air within the compressor’s air chamber. However, the lack of oil-based lubrication can result in less efficiency.

    Positive Displacement Blowers and Vacuum Pumps

    At Energy Machinery, we specialize in supplying high-quality blowers and vacuum pumps that fit each customer’s unique operational needs. Our positive displacement compression equipment includes these blowers and vacuum pumps:

    •   CycloBlower® Industrial Series Positive Displacement Blowers with Vacuum Pump. We offer several different positive displacement blowers with vacuum pump lengths ranging from 19-1/8 inches to 61 inches.
    •   DuroFlow® Industrial Series Positive Displacement Blowers with Vacuum Pump. Our selection of DuroFlow models includes a wide range of series and models to fit our customers’ needs best.
    •   4500 Series Positive Displacement Blowers with Vacuum Pump. Our inventory includes extension model options with different dimensions to suit any system or application requirements.

    Positive Displacement vs. Dynamic Compressors

    Dynamic compressors are another type of fluid compressor that uses different mechanics from positive displacement equipment. Dynamic compressors work at constant pressure levels instead of changing the fluid pressure between the inlet and outlet. Instead, dynamic compressors have different facial and radial designs, with high-velocity impellers that drive the gas through a diffuser where the air’s kinetic energy becomes static pressure.

     

    This mechanism can create high levels of horsepower. While positive displacement compressors are the most common type used in industrial facilities, dynamic compressors (or turbo compressors) may have more value in settings that need extremely high levels of power.

    Contact Energy Machinery for Your Next Positive Displacement Systems

    Positive displacement compressors ultimately generate higher pressure levels by decreasing the available volume for captured air. The decrease in volume raises the pressure and results in high-pressure air escaping through the outlet. Operators can increase or reduce the capacity to control the fluid’s pressure.

     

    If your facility needs positive displacement blowers and vacuums, Energy Machinery is here to help. We’ve offered high-quality supply and support services for nearly 50 years. Contact us today to learn more about our inventory or to place your order. 

  2. Positive Displacement Blower

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    Positive Displacement Blower

    Positive displacement blowers, or rotary blowers, circulate air by pulling a certain volume of gas into the rotary chamber and then pushing it out. Manufacturing and processing facilities use these blowers for a variety of applications, including aeration, vacuum processing, air extraction, and cleaning. 

    There are multiple types of blowers that can provide some degree of air circulation and displacement, including centrifugal blowers and regenerative blowers. However, it’s important to choose the right blower for different applications and energy use requirements.

    How Does a Positive Displacement Blower Work?

    Positive displacement blowers have two rotating impellers inside its central casing. These impellers—which can have two or three lobes—spin in opposite directions to force air into the blower and apply pressure to the air. The air enters the inlet side of the chamber, which is at atmospheric pressure and traps the air between two rotating impellers inside the machine. The blower then pressurizes and discharges the air to create circulation. The positive displacement process ensures that air cannot return to the chamber and that the airflow is unidirectional.

    These blowers have two key advantages:

    1.     They can move large volumes of air.
    2.     The systems are long-lived and straightforward, with relatively few maintenance demands.

    Positive Displacement Blowers vs. Centrifugal Blowers

    Both positive displacement blowers and centrifugal blowers force air movement. Whereas positive displacement blowers use impellers and displacement to force pressurized air through an outlet port, centrifugal blowers use kinetic energy to increase the speed of air moving through the unit. The unit then slows the air through a diffuser to convert the energy into static pressure. Facilities commonly reserve centrifugal blowers for ventilation, continuous gas transfer processes, and aeration applications.

    Regenerative Blowers vs. Positive Displacement Blowers

    Just like with positive displacement blowers, regenerative blowers use rotating impellers to draw air into the unit. Regenerative blowers then use centrifugal forces to accelerate the air and capture it between multiple internal blades. The spinning motion pushes the air from the top to the bottom of the blade configuration. Then, the blower pushes the air out of the unit at high speeds. 

    Regenerative blowers “regenerate” the air by turning it multiple times and increasing the pressure. These blowers are ideal for environments that need to have oil-free air; the spinning parts are self-lubricating and don’t release oils.

    Gardner Denver Positive Displacement Blowers at Energy Machinery

    Choosing the right blower type for a given application is essential. Different blowers work best to provide specific levels of pressure or the desired volume of air. Positive displacement blowers can provide a high degree of air volume movement at low-pressure levels. Energy Machinery provides the following positive displacement blowers:

    • CycloBlower: These positive displacement blowers deliver efficient, high-quality, and durable performance. They have shock-free compression, maintain a high-energy efficiency rating, and deliver oil-free air.
    • DuroFlow: The DuraFlow series of blowers have been used for nearly 50 years. These industrial blowers are durable, have a variety of installation and mounting options, and have multiple subtypes, so you can find the PSI levels that meet your needs.
    • 4500 Series: 4500 Series positive displacement blowers are rugged and can handle a wide variety of industrial applications. Each model comes with at-a-glance features and noise reduction options. 

    Energy Machinery, Inc. has specialized in providing air compression equipment and excellent customer service for over 45 years. We partner with major manufacturers to deliver the units and replacement parts that meet your facility’s requirements. Along with units and parts services, we also offer engineering services such as:

    • Energy audits
    • Leak detection analysis
    • Compressor room analysis, and more.

    Contact our team to learn more about our inventory of high-quality parts and to find the units that will fulfill your facility’s air displacement needs. You can also request a quote to start your order today.

  3. Refrigerated Air Dryers

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    Refrigerated Air Dryers

    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

    1. Non-cycling
    2. Cycling

    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 Dryers

    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.

    Contact Us for Your Application

    Need help deciding on the best one for your application? Contact us today and a product expert will get back to you immediately!

  4. Variable Speed Compressors

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    Variable Speed Compressors

    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

    Example:

    • 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!

  5. Benefits of Oil Free Air Compressors

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    Benefits of Oil Free Air Compressors

    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:

    Safety valve

    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.

    Compressor tank

    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.

    Air filter

    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.

  6. What is a Reciprocating Compressor?

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    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!

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About Us

Established in 1971, Energy Machinery, Inc. provides quality compressed air equipment and supports those products with exceptional customer service.

50+ years In business

50+ years In business

Distributor deals with over 20 major manufacturers

Distributor deals with over 20 major manufacturers

24 hour field service from certified technicians

24 hour field service from certified technicians

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