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Scroll-type air compressors are also commonly known as spiral air compressors because of their scroll or spiral-looking ergonomic structure. You can also call them to scroll vacuum pump or scroll pumps. It operates incredibly on the rule of the positive displacement method. The structure is more like a free-standing rolled spiral that is fixed to a solid flat base on one side.

Scroll compressors require very little maintenance as compared to other air compressors, making them easy to maintain expediently. Apart from the low maintenance, it tosses a very high-efficiency rate making it a more premium compressor type. Scroll-type air compressors also fall under the category of oil-free compressors, as there is no oil usage even in the gearbox; thus, no leakage of oil occurs.

Scroll or spiral compressors usually come in the market with very little weight as they have a very small size, which provides convenience to the user in handling. Scroll air compressor has one very unique feature; it also works as the scroll expander when it functions in reverse or opposite rotation, thus providing mechanical work while expanding compressed air, gas, or fluid.

Working Principle of Scroll Air Compressor

The working of scroll air compressors occurs in relatively three phases. When the moving scroll is rotated around the stationary scroll, the gas pockets are formed, and thus the air gets trapped in these pockets, which then further passes to the below discussed three phases.

Suction phase:

In this first shaft revolutionary phase, the motion scroll moves around the orbit of the fixed spiral; as in result, it creates the gas pockets. And when the gas pocket is formed, the suction port endows the outside air to get in a trap with these air spaces or gas pockets. When the first rotatory revolution is completed, the adjacent surfaces meet at the ends so that the air can’t move outside.

 Compression Phase:

This is the second shaft revolutionary phase; in this phase, the rotatory scroll again starts moving around the fixed scroll. As the air is sealed in the gas pockets, further motion causes the air to move to the inner gas pockets and in turn, the volume of the air is reduced and the air gets compressed. When this second phase completes, the maximum gas is compressed in the gas pockets.

Discharge phase:

This is the third shaft revolutionary phase; in this phase, the compressed gas which is present at the most inner pockets moves toward the discharge port with the help of further motion of scrolls. The compressed air then discharges out through the port which results in making the volume in gas pockets condensed to zero.

Once this procedure cycle completes, the three phases, namely suction phase, compression phase, discharge phase, again transpire instantaneously at comparative sequence.

Parts for Scroll Air Compressor

Talking about its structural parts, it consists of the steel welded cylindrical shell, where the compressor shell is enclosed. This is the reason these scroll air compressors are called fully hermetic compressors. 

A single scroll type air compressor ponders two spiral or scrolls. From these two scrolls, one is attached or fixed to the body of the compressor, and the other is in continuous motion. The scroll, which is fixed to the body basically provides a motion pathway to the moving scroll. The moving scroll rotated around the orbit of the fixed scroll. The motor shaft and discharge port are also contrasted that carries the operation.

In most compressors, the suction or discharge valves are used, but these scroll compressors don’t work on these suction valves; rather, they use the most efficient dynamic valves that also operate the compressor at a very high differential pressure rate. Thus, these dynamic valves also aid in increasing the functioning efficiency of these scroll compressors. Apart from the other compressors, this scrolls compressor does not have a piston to compress the air.

Advantages of Scroll Compressors

1. Due to the absence of a piston, the scroll air compressor endows the 100% compression of gas, thus reducing the cost of energy.
2. As it only has few moving parts, thus it helps the compressor to work quietly without making any sharp noise.
3. Due to less noise and vibration, it does not require the suspension of springs.
4. Having few parts and less friction also make the compressor more durable.
5. It has considerably less weight as compared to other compressors, making it easy to handle.
6. Scroll-type air compressors work very efficiently at all types of duty cycles, whether it of low duty or high duty.
7. It tosses a very high energy productivity ratio.
8.  The three working phases occur simultaneously, thus the flow of gas is very smooth which progressively reduces the gas pulsations.
9.  It proves very beneficial for cleaning purposes, as it contains no oil that makes it contamination-free.

Applications of Scroll Compressors

1. Scroll air compressors have vital use in all field systems of air conditioning. They are also used in the household conditioning sector as they produce very low noise. Moreover, it also proves very beneficial for commercial conditioning purposes.
2. Other than air conditioning purposes, these compressors are also used in laboratories. As laboratories require a small or noise-free compressor, it would be the best option because scroll air compressors are ultra-quiet.
3. It also offers wide use in the refrigeration of food and fruits.
4. Hospitals and medical centers also use these scroll compressors.
5. It is also used in water cleaning equipment as it is oil-free, so it carries out the cleaning purpose more effectively without any contamination.
6. Other than the above applications, these scroll-type air compressors have found a wide range of applications in heat pumps, vacuum pumps, transportation of trucks, and naval containers.

On a final note, we can articulate that the above-fabricated article encompasses all the momentous details about the scroll-type air compressors. All this information is contrived after thorough groundwork. So before buying any compressor, you ought to peruse this comprehensive article; it will for sure lead you to buy the best compressor.

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Buyers Guide: How to Pick the Perfect Scroll Compressor

Written by Industrial Stores Staff 04/24/23

A few years ago, you would only find scroll compressors in special applications, including hospitals, vacuum pumps, and car superchargers. Scroll compressors are much more common today, so the big question is how to choose the perfect scroll compressor for your needs.

Although they’re now more common, scroll compressors still have niche applications. Before buying one, you need to have a clear picture of what you expect it to do and what features it needs to have.

The easiest way to do this is to answer these questions:

• What will you be using the compressor for?
• What volume (CFM) and pressure (PSI) of compressed air do you need?
• Will you be operating the compressor continuously (100% duty cycle) or intermittently?
• What are your installation considerations?

Whether you’re a technician, contractor, or building manager, this guide on choosing the best scroll compressor is for you.
 

What Is a Scroll Compressor?

Scroll or spiral compressors are a type of positive-displacement compressor, which means they trap fluid in a fixed volume and force it to move through mechanical means.

They use two spiral elements that trap fluid between them and compress it. One of these elements is fixed, while the second one orbits within the vanes of the fixed element.

You can see this scroll-like element in the Copeland Digital Scroll Compressor below.

The only moving parts in the compressor are the rotary scroll and motor. Emerson, the manufacturer of Copeland scroll compressors, estimates that it has 70% fewer moving parts compared to conventional models.

With so few moving parts, scroll compressors are much more reliable and quiet compared to reciprocating models. Scroll compressors can also run without lubrication, which reduces the chances of contaminating air or refrigerant with water or oil.

These benefits, paired with their small size, make scroll compressors perfect for sensitive applications. Common uses of scroll compressors include air conditioning, automobile superchargers, food and fruit refrigeration, vacuum pumps, and marine containers.

How a Scroll Compressor Works

Scroll compressors use an orbital motion to compress crescent-shaped pockets of fluid caught between the vanes of the two scrolls.

Watch this outstanding video by Thomas Schwenke to see how this happens.

Due to the way they operate, scroll compressors don’t need a suction valve (although they usually have a special one-way discharge valve). Their design is simple but powerful, giving them a highly efficient compression process.

Important Features and Benefits of Scroll Compressors

• High efficiency - Scroll compressors are 10 – 15% more efficient than reciprocating compressors.
• Few moving parts - With up to 70% fewer moving parts, scroll compressors require much less maintenance than rotary or reciprocating compressors.
• They can be oil free - The moving and fixed scrolls don’t need to touch to compress fluid, so they can be oilless to minimize contamination.
• Compact - Scroll compressors can be small and lightweight while still achieving a high compression ratio, making them perfect for portable applications.
• Smooth flow - Unlike piston-type compressors that deliver compressed gas in pulses, scroll compressors deliver smooth flow because suction, compression, and discharge occur simultaneously.

You will get smooth, reliable, and efficient compression with a scroll compressor. Learn more and explore various brands as you check out the latest prices.

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How To Select the Right Scroll Compressor

1 - What Kind of Work Will You Be Doing With the Scroll Compressor?

The most important factor when choosing a scroll compressor is the type of work for which you need it. There are several reasons why this is necessary:

• Do you need a lubricated or oilless compressor? If air quality is a concern, choose an oilless system with an ISO Class 1 or Class 0 air quality rating.
• Do you need a continuous supply of compressed air (continuous duty) or will you be using the unit intermittently? Before buying a unit, check its technical specifications to see how much downtime it needs during each hour of operation.
• If you need a more controlled flow of air, consider installing a receiver tank to hold pressurized air. The tank will ensure a constant supply of air without having to run the compressor all the time.
• Do you have any special requirements? For example, if you want completely dry compressed air, choose a unit with an inbuilt air dryer and in-line filter.

Scroll compressors are usually single-speed. That means they only operate at full capacity, but you can also buy units with variable capacity such as this Copeland Scroll Tandem Compressor.

If you’re replacing an air conditioner compressor, consider installing a model with variable capacity. These allow exceptional temperature and humidity, typically within +/- 0.5 °F. This ensures more comfort in homes and minimal food spoilage in refrigeration systems.

When replacing an existing unit, look for a unit with the same technical specifications.

2 - Calculate the Volume and Air Pressure You Need

The second most important factor is your air consumption. You need to determine the total airflow you need to power all your tools and equipment.

Check manufacturer specifications and pressure requirements for all your pneumatic tools/machinery. Your scroll compressor should be able to handle the highest PSI required for your equipment during peak operation.

For the airflow in cubic feet per minute (CFM), add up all the CFM requirements for all equipment that you will be running simultaneously. Add a 30% safety margin, and you will have a minimum CFM value for your scroll compressor.

With competitive price and timely delivery, Leling sincerely hope to be your supplier and partner.

If you’re buying a compressor for air conditioning, look for manufacturer guidelines on what compressor capacity to buy.

3 - Figure Out How Much Power You Need

Scroll compressors come with a motor already mounted, so you don’t need to calculate horsepower figures. For example, the Danfoss H-Series Scroll Compressor below comes as a complete package with an internal motor and terminal box.

However, you need to figure out power supply requirements including voltage, current, circuit safety, and control features. Check manufacturer guidelines for these details and be careful to follow them to the letter, as scroll compressors can be sensitive to bad connections.

In fact, some of the most common causes of compressor failure include poor electrical connections and motor problems caused by electrical problems.

4 - Figure Out Your Ideal Duty Cycle

Scroll compressors have a big advantage because they can operate for extended periods without excessive wear. The best models only require a few minutes of downtime for an hour of continuous operation.

If you need a continuous supply of compressed air/refrigerant, make sure that the scroll compressor you choose has the right duty cycle. For example, the Danfoss 121L Scroll Compressor below can handle 12 start/stop cycles and requires a 3-minute time-out per hour.

Turning a compressor on requires a large current draw from the mains and can cause increased equipment wear. If you have too many start/stop cycles, at some point it becomes more economical to run the unit continuously and eliminate the start/stop operations.

The rule of thumb is that you have to start and stop a compressor more than eight times an hour, consider installing a receiver tank or run it continuously.

Expert Tip: The compressor you choose must always be oversized for your particular applications. Better still, install a tank for your compressor so it doesn’t have to run all the time.

5 - Installation Considerations

Scroll compressors are so quiet that you can install them close to the point of use. However, there are other installation considerations to think about.

The most obvious one is the electricity supply. Larger units often require three-phase power, while small ones operate off single-phase mains. Heat is also a major factor because scroll compressors generate a lot of heat and require some form of cooling.

Therefore, it’s worth taking the time to pick a scroll compressor that will run off the electrical supply you have. Also, check the space where you will be installing the unit. It needs to have good air circulation for cooling, and some manufacturers even recommend placing it near a fan or window for better cooling.

You should also think about what control system you need. For example, an automatic start/stop system based on air pressure levels will be necessary if you have a receiver tank.

Expert Tip: If you have to start and stop the compressor more than eight times an hour, it’s more economical to run the unit continuously to reduce the high current drawn at starting.

Price Range of Scroll Compressors

You can get a good single-speed scroll compressor for just under $800, while premium variable-speed models with sophisticated controls can reach $5,000 or more.

Apart from this, the prices of scroll compressors vary only slightly from brand to brand depending on performance factors such as flow and pressure.

The table below shows the average prices of four scroll compressor models we have at Industrial Stores.

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What Others Said About Industrial Stores

Our happy customers love our friendly service, fast shipping, and comprehensive inventory. 

Some of the compliments and positive reviews that come up most include:

• Service beyond the obvious, always ensuring customer satisfaction
• Fast and convenient shipping with order tracking, giving you peace of mind
• Cost savings by finding you more affordable alternatives

"Thank you so much for your hard work and concern, really appreciated."
— Luis S. Valverde, Thermo Air Inc., Hollywood, Florida

"I couldn't be happier to have saved hundreds of dollars."
— Ruben Marquez, Madison, WI

"I have the part, it was here early AM - THANKS SO MUCH."
— Teresa Browder, Oak Farms Dairy, Houston, Texas

People Also Ask

How do I know what size of compressor I need?

The size of air compressor you need will depend on your airflow needs in cubic feet per minute (CFM), as well as the pressure ratings of your equipment. This information will be available for each piece of pneumatic equipment you are using in their user guide.

Sum up all the CFM flow requirements for all the equipment you will be operating simultaneously and add a 20 – 30% margin. Remember to use the higher CFM and PSI values for your equipment to make sure you can meet peak demand.

Are scroll compressors the best?

Scroll compressors are quieter, more efficient, and provide more consistent airflow than other types of compressors. However, this doesn’t mean they are the best since they also have a few shortcomings.

Each type of compressor has applications to which it is best suited depending on its features. The table below shows some important features of the four main types of compressors.

Why are there no large scroll compressors?

Due to their design and working principle, scroll compressors are usually small in size. They tend to have leakages between the vanes of their scrolls, and larger units leak more and lose efficiency.

Also, large displacement scroll compressors require massive scroll elements, making them impractical.

Do scroll compressors require oil?

Scroll compressors can be lubricated or oilless. They come in different designs, with somewhere the scrolls do not actually touch. This eliminates the need for flooding the compressor with oil or lubricant, providing clean air.

However, there are also lubricated and even oil-flooded scroll compressors, especially those that require a high compression ratio.

Let’s Get You the Scroll Compressor You Need Today

The way scroll compressors work is simply genius. The interlocking vanes can compress fluid with almost 100% efficiency and very little noise. Plus, they have very few moving parts and are extremely reliable and long-lasting.

That being said, scroll compressors have limited flow and pressure output. They are great for niche applications where clean air or refrigerant is required such as air conditioning, food processing, and medical laboratories, among others.

If you’re looking to buy a scroll compressor, you need to make sure that the one you choose will supply enough airflow at the right pressure for all your equipment. It also needs to meet your installation and performance needs.

Here at Industrial Stores, our expert staff are well-equipped to help you find the best scroll compressor for your needs. We will also source the right unit for you, get you reduced prices, and deliver the unit to you quickly and safely.

Shop for scroll compressors at Industrial Stores today to discover the best prices.

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