Screw Air Compressor
Zhejiang Meizhoubao: Your Professional Screw Air Compressor Manufacturer!
Zhejiang Meizhoubao Industrial & Commercial Co.,Ltd. is one of the air compressor manufacturers in China that produces all kinds of air compressors. We are a modern enterprise combining with research, development, manufacture and trading. Meanwhile we have leading-edge workshop, leading-edge production assembling lines, precise testing equipments and skilled staffs.
Rich Experience
Founded in 2003, our company has 20 years experience in air compressor and 15 years OEM experience for more then 100 clients around the world.
Professional R&D Capability
There are professional R&D teams and independent research and development under the leadership of human resources such as Professor Xu Shiwei from the School of Mechanical and Vehicle Engineering of Hunan University and doctoral supervisor.
Integrated Team
Our company is an enterprise integrating production, scientific research, production, domestic and foreign trade and warehousing. The company team has sales center, foreign trade department, domestic sales department, R&D center, production department and after-sales department.
Strong Production Capacity
Our company has produced 1 million air compressors annually, with more than 200 product models. The products sell well all over the country and are exported to more than 60 countries and regions in the world.
Complete Qualifications
Our company designs and manufactures high quality products with 12 R&D engineers. We have CE, CCC, ISO9001, ROHS certificate and so on.
Introduction to Screw Air Compressor
A rotary screw compressor is a type of air compressor that uses two rotating screws (also known as rotors) to produce compressed air. Rotary screw air compressors are clean, quiet and more efficient than other compressor types. They are also supremely reliable, even when used continuously. This makes screw compressors the preferred solution for professional and industrial applications across the globe.
Working Principle of Screw Air Compressor
Intake
Air enters the compressor through an inlet filter, removing dust and debris to prevent internal component damage.
Compression
The heart of the compressor lies in the intermeshing male and female rotors. As these rotors rotate, air gets trapped between their lobes and gradually compressed as the volume between them decreases.
Injection (Oil-injected compressors only)
In oil-injected screw compressors, oil is injected during this stage for cooling, lubrication, and sealing the clearances between the rotors and the housing.
Separation (Oil-injected compressors only)
After compression, the air-oil mixture passes through an oil separator where the oil is separated from the compressed air.
Aftercooler
The compressed air then flows through an aftercooler which removes moisture condensation through heat exchange, preventing corrosion and ensuring clean, dry air output.
Discharge
Finally, the compressed air is delivered to the application through a discharge line and receiver tank (for storage).
Basic Components of Screw Air Compressor
Rotors /Rollers
Rotors or rollers are the heart of the rotary screw compressor. They come in pairs and are inside the cylinders of the compressor. Rotors rotate at high, sweeping speeds creating a pipeline for suctioned air to move through, compress, and discharge out of the system.
Compression Cylinders
Rotary screw air compressors include the main compression cylinder housing the rollers. When air is collected, it runs through the cylinder’s chamber and into the interlocking, spinning rotors.
Air Filters
Air filters are one of many layers of filters within the rotary compressor. The air filter sits inside the compressor’s opening valve where it catches dust, particles, and moisture. This prevents them from damaging to the inside of the machine.
Oil Filters
For oil-lubricating air compressor screws, oil filters are placed both within the rotating chamber walls and near the discharge valves. These filters purpose is to sift oil from the compressed air. Oil lubrication is necessary as it offers cooling needed for compression machines, which tend to produce high heat.
Bearings
Bearings are on both rotor ends to help rotors stay in place. This is due to rotor ends rotating constantly.
Suction Valve
This component sits on top of the compressing unit and is responsible for initial gas retrieval. During the unit’s stage control, the suction valves open to allow air to move inside.
Discharge Valve
The discharge valves sit on the opposite end of the suction valve and start the end of the compression cycle. Now-pressurized air is administered in the discharge valve and is released into either a holding, storage tank, or discharge pipe for immediate application.
Motor
Motors power the rotations of the rollers automatically, helping to power the machine’s entire compression capabilities.
System Control
This component is necessary for when operators read and gauge the unit’s overall health and output. A system control displays and monitors different components of a compressor – operating, idling, and stop parameters.
Storage Tanks
Storage tanks receive now-condensed air from the discharge valve where it sits and maintains pressure until it needs to be used.
Separators
In oil injection compressors, separator tanks are used as another defense tactic against oil and gas mixtures. T can damage the purity of the compressed gas stream.
Gaskets & Seals
Gaskets and seals ensure a rotary screw compressor’s interior and exterior are locked, sealed, and leak-free.
Common Types of Screw Air Compressor
Oil-Injected Screw Compressors
In these compressors, oil is injected into the compression chamber to lubricate and keep all the elements within permissible operating temperature limits. Although oil is the preferred choice because of its lubricating and sealing properties, synthetic lubricants are also used, particularly in applications that involve higher temperatures.
Using oil or other lubricant as a medium of heat transfer to remove some of the waste heat resulted from the compression process will reduce the amount of vapor in the compressed air or gas. This will minimize leaks from returns into the compression chamber during the discharge. Some compressor models also include a fan on the drive motor shaft that provides air flow in order to cool the lubricant as well as the other elements of the compressor.
To remove the lubricant from the compressed air or gas, most oil-injected compressors use a centrifugal separator. However, a small amount of lubricant or oil (oil carry-over) often passes through the separator, together with the compressed air or gas. The oil or lubricant is filtered and cooled before being re-injected into the compression chamber. In applications that require compressed air or gas at lower temperatures, the air or gas can be run through an additional aftercooler.
Oil-Free Screw Compressors
In oil-free rotary screw compressors, the rotors do not come into contact to create friction. Thus, they do not require lubrication within the compression area. Because the compressed air or gas is completely oil-free, these compressors are suitable for applications that cannot tolerate contamination of the compressed air or gas with oil or other lubricants.
However, the bearings must be adequately lubricated. The lubricant will protect bearing surfaces against corrosion, reduce friction, inhibit wear, and ensure efficient and reliable operation.
Because oil-free compressors tend to heat up fast, compressing air or gas in just one step can rise the temperature above the limits recommended. To avoid this—as well as any potential leaks in the compression chamber during the discharge—compression is done in two stages.
Each stage compresses the air or gas gradually, by several bars; the air or gas reaches the desired pressure level at the end of the second stage. To further remove the waste heat, most designs are built with an intercooler between the two stages and an aftercooler after the second stage.
Two-stage Screw Compressors
Two-stage lubricated rotaries compress air in two steps. Step or stage one takes atmospheric air and compresses it part way to the discharge pressure target. Step or stage two ingests the air at the inter-stage pressure and compresses it to the discharge pressure target. Compression in two stages improves efficiency, but adds cost and complexity given the additional rotors, iron and other componentry involved. Two-stage is generally offered in the higher HP ranges (100 to 500 HP) because the improved efficiencies result in larger dollar savings when air use is large.
Single-stage Screw Compressors
Single stage versus two-stage, it is a relatively straightforward calculation to determine what the payback will be from the more efficient but more costly two-stage unit.
Remember that the energy cost of operating a compressor is the largest expense over time, so evaluation of a two-stage machine is certainly worth a look.
Lubricated Screw Compressor
The lubricated rotary screw compressor has been the most popular technology for the majority of industrial plant air applications from 20 to 500 HP and from 80-175 PSIG. These compressors offer unmatched versatility and adaptability to various operational demands. Their efficient design ensures a continuous and reliable supply of compressed air, crucial for sustaining seamless production processes.
Characteristic of Screw Air Compressor
High Efficiency
Screw type air compressors offer excellent performance in terms of energy efficiency. Well-designed screw type compressors operate cost-effectively and efficiently by minimizing energy consumption. In turn, this reduces energy costs and minimizes environmental impacts.
Continuous Air Flow
Screw type compressors provide a constant and continuous flow of air. This feature is ideal to fulfil the requirement for constant flow of compressed air in industrial applications. Continuous air flow ensures that production processes run efficiently and without interruption.
Low Maintenance Costs
Screw type air compressors are notable for their low maintenance costs. Constructed from components that are built to last in general, screw compressors do not require regular maintenance and can operate smoothly for a long period of time. This reduces operating costs and improves operational efficiency.
Extended Service Life
Screw type compressors have a robust construction, and this provides them with a long service life. Screw type air compressors made of quality materials provide advantages in terms of durability. Their long service life reduces the need for costly refurbishment or replacement operations.
Advantages of Screw Air Compressor
Less Moving Parts
A screw air compressor is not comprised of many moving parts. This is due to the advanced technologies used for producing compressed air. The reduced number of parts call for more efficiency and productivity of the compressor.
Easy Maintenance and Durability
When we talk about screw air compressors, we always talk of durability. Having said this, this kind of air compressor requires very little maintenance and the lifespan on these air compressors is more. The most important feature of a rotary air compressor is that it can easily stay five to six years more than its other counterparts. Most of the parts of the rotary air compressor comes with a lifespan of ten years and that is an added advantage to this machine.
Low Level of Noise
Industries where already a lot of noises are prevailing, an air compressor which produces low level of noise is always welcome. As compared to other air compressors, rotary air compressor produces less noise and thus, the workers are spared of bearing heavy noises all around.
Minimum Oil Carryover
There is oiled and non-oiled air compressor but when you pick up the oiled rotary air compressor, the oil carryover is minimum. Less oil means less of mess and it is easy to maintain.
Lighter and Portable
Screw air compressors are ideal for the industries where it needs to be transferred from one place to another. Screw air compressors are light in weight and they are easily portable.
No reduction in capacity over a period of time
With more and more use, any machine can reduce its performance but with screw air compressors, it is not so. Even with extensive use every day, the performance of screw air compressors with not reduce.
Manufacturing
Many manufacturing facilities rely on screw compressors to power production equipment, conveyors, and packaging lines. Rotary screw compressors provide consistent airflow and pressure for robotic production applications in manufacturing sectors such as automotive, aerospace, and general fabrication. Manufacturing plants also use compressed air to lift and move heavy parts and power manual tools. Other applications in manufacturing include:
● Power cleaning.
● Surface preparation (e.g., abrasive blasting or vibratory finishing).
● Paint lines/spray booths.
● Plastic forming/blow molding.
● Cleaning and deburring.
Process Industries
Process industries, including chemical manufacturing and pharmaceutical manufacturing, rely on rotary screw compressors for both process air and to power machinery and conveyors. Air for pharmaceutical and process industries may need to meet very strict standards for purity. Screw compressors can be used to power applications such as:
● Operating pumps that move liquid products through stages of production.
● Aeration and mixing of liquids and powders or liquid processing/agitation.
● Product drying.
● Maintaining air curtains to prevent mixing of gases and vapors.
● Recharging desiccant dryers, nitrogen generators, or carbon filters.
● Membrane filtration.
● Equipment cleaning.
● Packaging lines.
Food and Beverage
Food and beverage manufacturers may use screw compressors in a variety of ways, from product blow-off and cleaning to packaging lines. A rotary screw compressor provides consistent and reliable air for food and beverage applications, including:
● Air-jet food processing (e.g., cutting, peeling, and cleaning of produce).
● Food drying or dehydration.
● Cooling of baked goods.
● Carton forming, filling, and vacuum sealing for packaging.
● Pneumatic conveying (e.g., bottling lines).
Agriculture
While small family farms may be more likely to use a reciprocating or piston compressor, large-scale commercial farming can benefit from the high efficiency and high CFM of a rotary screw compressor. Applications for screw compressors in farming include:
● Powering pneumatic conveyors to transport grain and other harvested products from the field to storage silos.
● Spraying pesticides, herbicides, and fertilizer.
● Operating milking robots and other dairy machinery.
● Aerating tanks for wastewater treatment.
● Clearing irrigation lines.
● Ventilating greenhouses.
Oil & Gas
Rotary screw compressors are widely used throughout the energy sector for a variety of purposes. In the oil & gas industry, screw compressors are used to power drilling equipment and pneumatic systems for transporting drilled oil. Compressed air may also be used to power equipment for compressing natural gas and refining petroleum. Other uses in the energy sector include:
● Gas re-injection for enhanced oil recovery.
● Boosting gas flow through high-pressure pipelines.
● Petrochemical synthesis.
Factors to Consider when Choosing a Screw Air Compressor
Stationary vs. Portable
Portable compressors are used where air-powered equipment may be needed in different places and electrical power is not readily available. Portable compressors can be diesel engine or electric motor driven. Portable compressors are commonly (but not always) built on a chassis with wheels. Exercise caution when using diesel driven compressors, as they often do not come with aftercoolers and can overload dryers with hot, wet air, ultimately causing damage to downstream equipment and tools.
Indoor Use vs. Outdoor Use
A compressor used outdoors will encounter a wider range of ambient air temperature and humidity, and perhaps higher dust levels. Outdoor installation generally provides easier access to cooling and avoids the need for noise mitigation, but may require additional environmental protections.
Drive Type System
There are three options available: belt, gear, or direct driven. Belts and gears provide versatility in manufacturing but incur more transmission losses, thereby lowering the overall efficiency of the air compressor system. Many compressors now come with the option for a variable frequency drive in order to better manage motor power consumption under varying load conditions.
Air Volume
Air delivery rate is specified in CFM. As CFM is related to ambient temperature and atmospheric pressure, several specifications reference Standard CFM (SCFM) for enabling comparisons.
Pressure
This is specified in PSI. Most air-powered equipment requires 70-90 PSI. Be mindful of machines that require a higher pressure than 100 PSIG; this means there are internal regulators.
HP
While not correlating exactly with maximum CFM, HP is an indicator of compressor size. Although it varies by country, in the United States, most industrial compressors require a 480 volt 3-phase electrical connection; however, 208 and 230 volt 3-phase connections can be found under 50 HP. When you get down to the smallest of the rotary screw compressors of 5 and 7.5 HP units, you can find 230 volt single phase. Sufficiently sized electrical distribution and breakers are required for reliable operations. Always consult your local licensed electrician.
Tank Size
The tank is the reservoir of compressed air. Systems where air demand can fluctuate widely need a larger reservoir to prevent excessive compressor cycling. There are several rules of thumb in regard to compressor sizing; you will require at least 4-6 gallons of storage capacity per HP. But honestly, there are several factors to take into account when sizing a receiver tank, including budget, floor space, control type of compressors in the system, whether networked or working off a pressure band, as well as the size of the compressors. You need the tank to be large enough to keep a critical system pressure in your plant, while allowing your backup compressor to come online if something were to happen to your primary compressor. Think of it like a water tank; you need your backup pump to spin up and start pumping water up to the tank before the tank runs dry. A compressed air audit (link to audit article) will help you better understand the demands of your compressed air system, in order to plan for such an event.
Cost
The price of a compressor is related to its capacity and features. Note that during the lifetime of a compressor, energy costs will be far greater than the purchase price. For this reason, consider paying more for higher efficiency. Do not hesitate to ask for a preventive maintenance quote when looking at a new compressor.
FAQ
Q: What is a screw air compressor?
Q: What is the working principle of rotary screw air compressor?
Q: What is a screw air compressor composed of?
Q: What are the differences between oil-free and oil-injected rotary screw elements? And why is an oil-free element more expensive compared to an oil-injected element?
Gaps and clearances allow the compressed air to flow back the 'wrong way'. It lowers the efficiency and performance of the air-end.
Because the oil-free type compressors don't have any oil, the clearance between the rotors and the housing must be much smaller compared to oil-injected type screw elements. Because of this the price of an oil-free air-end is much higher.
The needed maximum clearance depends on the rotor diameter and is about 1 thousand of the diameter, max. So if the diameter of the rotor is 200 mm, the clearance would be only 0,2 mm, which is pretty small for such a complicated shape.
Besides this, the oil-free elements require extra pockets and channels for cooling water. The oil-injected type element is cooled by the injected oil and doesn't need extra cooling water.
Q: What are the benefits of rotary screw air compressors?
They deliver a continuous and steady supply of compressed air, which is essential for applications that require a consistent flow of air. Their design minimizes fluctuations in pressure, leading to improved efficiency and reduced energy consumption.
Continuous Operation
Rotary screw compressors can operate continuously without the need for frequent starts and stops, which can extend the lifespan of the compressor and improve overall system reliability.
Adaptability
Rotary screw compressors can operate in both high and low conditions, even in areas where safety restricts other energy sources.
Easy to Maintain
Their minimal moving and contacting parts make maintaining compressors easy, reducing wear, extending service intervals, and simplifying routine checks and repairs.
Low Noise Levels
These compressors are generally quieter than reciprocating compressors, making them suitable for environments where noise is a concern, such as indoor workplaces.
Q: How does an screw compressor operate?
As the impellers rotate, they trap and isolate air in the cavities between the rotors, thus moving the air down the chamber.
The chamber decreases in size and is moved away from the opening valve. As the volume decreases, the pressure increases.
Pressurisation builds and thus the air is condensed.
Air pressure will trigger the compressor’s discharge valve to open, allowing the pressurised air to enter a receiver or other holding tank.
Air is compressed and can be transferred to downstream equipment such as dryers and oil/water separators for drying and contamination removal.
Q: What functions do oil of the screw compressors perform?
Q: What are the benefits of screw compressors?
Provision of continuous airflow and constant pressure.
Lower vibration and noise levels.
Longer uptime and lower maintenance requirements.
Flexible use and easy installation.
Easier integration with automated control systems.
Possibility of customization to suit different capacity and pressure requirements for various industrial areas.
Compact design for a smaller footprint and easy installation.
Q: How can I maintain the screw air compressor?
Checking oil.
Changing and flushing oil.
Replacing oil filters.
Replacing air intake and inline filters.
Changing the oil/water separator.
Inspecting and replacing belts or drive train parts.
Lubricating motor bearings.
Inspecting and adjusting controls.
Cleaning and maintaining air compressor coolers and heat exchangers.
Q: How often are filters changed for a rotary screw air compressor?
Q: What are rotary screw compressors used for?
Rotary screw air compressors are not just popular as stationary models. Mobile units, for example those mounted on trailers, are used on construction sites to operate pneumatic tools, or sand blasting and painting systems. In addition, due to their ease of installation and robustness, they are an excellent fit for mining operations in remote locations.
Q: What are the main types of screw air compressor?
Oil-injected rotary screw compressors are the most common, since they are the cheaper ones of the two types.
Oil-free screw compressors are only used in applications where to compressed air must be 100% oil free (usually in food-processing plants, chemical plants, etc).
Q: How can screw air compressor benefit industry?
Screw air compressors are designed to use less energy than other types of compressors, making them a more cost-effective solution for industrial applications.
Reliable Performance
Screw air compressors are known for their reliability and durability, delivering a continuous and steady supply of compressed air without interruption.
Reduced maintenance costs: Screw air compressors require less maintenance than other types of compressors, reducing downtime and maintenance costs for businesses.
Consistent Output
Screw air compressors deliver a consistent output of compressed air, ensuring a reliable supply for industrial applications that require a steady flow of compressed air.
Versatility
Screw air compressors can be used for a wide range of industrial applications, from automotive and manufacturing to construction and more.
Low Noise Level
Screw air compressors are designed to operate quietly, making them a good choice for industrial settings where noise pollution is a concern.
Improved Productivity
By delivering a steady supply of compressed air, screw air compressors can help improve productivity in industrial settings, reducing the time required to complete tasks and increasing overall efficiency.
Q: What precautions should be taken when using oil-free screw air compressors?
The user should set up a protective grounding wire for the oil-free screw air compressor to ensure that the metal shell of the air compressor is in good contact with the ground, and the grounding resistance should meet the standards.
The oil-free screw air compressor should be placed in a ventilated and stable air compressor room and cleaned regularly.
When the air compressor makes serious abnormal noise, air leakage and odor, the operation of the air compressor should be stopped immediately, and the cause can be found and the fault is eliminated before it can be operated again.
When starting the oil-free screw air compressor again after an abnormal shutdown, pay attention to whether the pressure inside the air compressor has been cleared to avoid starting under pressure and causing the air compressor to trip.
Q: What factors should be considered when choosing screw air compressors?
Q: What is the difference between a screw and piston compressor?
Another difference is the moving parts as the screw compressor has two moving parts which are not in contact while the piston compressor has a lot of moving parts. The screw compressors operate at a lower temperature and integrate a good cooling system.
Q: What kind of oil should I use for oil-injected screw air compressor?
Both mineral and synthetic oil are suitable for air compressors. Normally, oil with the mineral origin is perfect for compressors with small or medium dimensions, which works from time to time. They are mostly chosen for compressors used at home. Instead, if your compressors find professional or industrial applications, you can go for synthetic oil, which offers more protection against overheating.
Q: What factors should I consider for installation of a rotary screw compressor?
The amount of space available for installation, including the location of the compressor, air receiver tank, and any other related equipment, should be taken into account. In particular, the location and surrounding space need to consider heat dissipation for the air compressor. If the compressor is located inside, make sure the compressor room is well-ventilated and there is plenty of airflow to carry excess heat away to prevent the air compressor overheating. If the compressor is located outside, proper weatherization may be needed to keep the compressor running properly in cold weather.
Power supply
The compressor must have access to a suitable power supply to operate correctly, including the correct voltage, amperage, and phase.
Distribution system: A well-designed compressed air distribution system is essential to ensure efficient and effective delivery of compressed air. The size and length of the pipes, as well as the materials used, should be selected based on the specific requirements of the application.
Air quality
The quality of the incoming air, including the presence of contaminants, should be assessed to determine if intake filtration or other air treatment is required.
Noise
Industrial air compressors can generate a significant amount of noise, so the location and design of the installation should take into account any potential noise pollution issues and reduce compressor noise where possible.
Safety
The safety of the compressor and its components, including the air receiver tank, should be a top priority during installation. This may include ensuring that the compressor is located in an area where it will not pose a hazard, installing appropriate safety features like pressure relief valves, and ensuring that the compressor meets all relevant safety regulations.
Q: Can rotary screw compressors be used for heavy-duty applications?
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