Piston compressors, also known as reciprocating compressors, are commonly used in various applications due to their simplicity and effectiveness in delivering compressed air. It's important to evaluate several factors to ensure you select the right equipment for your specific requirements.
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For applications requiring intermittent use and lower volumes of air, we recommend the CR series of cast-iron piston compressors, which are particularly suited for automotive and light manufacturing applications.
This compressor operates using a simple mechanism where the air is drawn into a cylinder and compressed by a moving piston. They are known for their reliability and are particularly suitable for applications that require high pressure and lower volumes of air. The operation can be affected by pulsation and valve operation, which can lead to increased wear and decreased efficiency.
The capacity can be controlled by various methods such as variable-speed drives and suction valve unloaders. These methods help maintain the required compressed gas delivery under variable process conditions. It's important to choose a compressor with appropriate capacity control features to ensure efficient operation and avoid issues such as high discharge temperatures and overload in the last stage of compression.
These compressors can generate significant vibration and noise during operation. The noise level can be a concern in workplace environments, and it's essential to consider the installation location and any necessary sound attenuation measures. Atlas Copco's G/GX series compressors offer a quieter alternative, making them suitable for use in smaller businesses and workshops.
Due to their design, there are more moving parts compared to rotary screw compressors, which can result in more wear and tear. This means they may require more frequent maintenance. However, their simple design also makes them easier to maintain. It's crucial to consider the maintenance requirements and ensure that you have access to the necessary service and parts to keep the compressor running efficiently.
When it comes to temperature, they tend to run hotter than rotary screw compressors, which can impact their performance and the quality of the compressed air. Proper temperature control and cooling systems are important to prevent overheating and to ensure the longevity of the compressor.
Piston compressors generally require more space and may not be as energy-efficient as rotary screw compressors, especially when not running at full capacity. It's important to consider the space available for the compressor and to select a model that matches your air demand to avoid energy wastage.
Rotary screw compressors are a popular choice for continuous operation and high-volume air needs. They are known for their energy efficiency, reliability, and lower maintenance requirements than piston compressors.
For continuous operation and higher volumes of air, Atlas Copco's rotary screw compressors are more appropriate. The GA and GA FLX series of oil-injected rotary screw compressors is recommended for its reliability and energy efficiency. These compressors can operate at temperatures up to 46 degrees Celsius and maintain efficiency over time.
Here are some specific aspects to consider when choosing a rotary screw compressor:
Rotary screw compressors are generally more energy-efficient than piston compressors, especially when equipped with a Variable Speed Drive (VSD). VSD compressors, like the third generation of our VSD compressors, the GA VSDs, adjust the motor speed to match air demand, reducing energy wastage. However, when the initial investment cost is too high for these smart VSD compressors, the GA FLX series of dual-speed compressors is the ideal energy-efficient alternative.
Isentropic efficiency is a measure of a compressor's efficiency, with higher percentages indicating better performance. The highest isentropic efficiency for rotary screw compressors is about 92%, which can lead to significant energy savings
While the initial cost of a rotary screw compressor may be higher than that of a piston compressor, the TCO is often lower due to increased efficiency and lower maintenance costs. The TCO includes purchase price, energy consumption, maintenance, and any downtime costs
Rotary screw compressors are known for their reliability and durability. They have fewer moving parts, which means less wear and tear and more consistent performance over time.
This reliability can be crucial in demanding industrial environments where downtime can be costly.
Noise levels are an important consideration in the workplace. Rotary screw compressors tend to operate more quietly than piston compressors, allowing them to be placed closer to workspaces without causing significant noise disruption.
Maintenance is simpler for rotary screw compressors due to their design, which has fewer moving parts. This can result in lower maintenance costs and less frequent service needs. However, it's important to consider the availability of service technicians and spare parts for the chosen brand and model.
When comparing piston and rotary screw compressors, it's important to understand their operational differences and how these relate to their suitability for specific tasks. Piston compressors, also known as reciprocating compressors, are typically used for applications that require short, intense bursts of air. In contrast, rotary screw compressors are designed for applications that need a steady flow of air over extended periods.
Piston compressors work by drawing air into a cylinder and compressing it with a reciprocating piston. They are generally best for lower volume air needs and have a duty cycle of about 60-70%, meaning they need to shut down periodically to prevent overheating.
Rotary screw compressors, on the other hand, use two interlocking rotors to compress air and are fluid cooled, allowing for 100% duty cycle and continuous operation without the risk of overheating.
Rotary screw compressors are typically more energy-efficient than piston compressors, delivering more air per unit of input energy. For example, piston compressors generally deliver 3-4 cubic feet per minute (cfm) per horsepower (hp), while rotary screw compressors deliver 4-5 cfm per hp. This efficiency is particularly beneficial where electricity costs are high.
The quality of compressed air is another consideration. Piston compressors operate at higher internal temperatures, which can lead to more moisture in the compressed air. This may require additional drying and cleaning components. Rotary screw compressors run at lower temperatures and often come with built-in aftercoolers to reduce the air temperature, resulting in better air quality.
Rotary screw compressors have fewer moving parts than piston compressors, which translates to less wear and tear and lower maintenance requirements. While piston compressors are simpler in design and may be easier to maintain, they typically require more frequent service due to more moving parts.
Rotary screw compressors operate more quietly and require less space compared to piston compressors, making them suitable for closer proximity to workspaces.
The initial cost of a rotary screw compressor may be higher, but the total cost of ownership can be lower due to its increased efficiency and lower maintenance costs over time. This includes the purchase price, energy consumption, maintenance and downtime costs.
Rotary screw compressors generally have lower operating costs and are more energy-efficient in the long run, especially for continuous use scenarios. However, piston compressors might offer savings for smaller or less frequent applications.
Atlas Copco's GA series with VSD technology is recommended for its energy efficiency. The GA 5-37 VSDˢ model, in particular, can achieve significant energy savings and has a design that minimizes energy consumption.
The duty cycle of an air compressor is a crucial factor to consider when selecting the right compressor for your needs. It refers to the percentage of time a compressor can operate continuously without needing a rest period to cool down. This concept is particularly important when comparing different types of compressors, such as rotary screw and piston compressors, as it directly impacts their suitability for various applications.
The duty cycle is calculated by dividing the compressor's run time by the total cycle time (run time plus rest time), expressed as a percentage. For example, if a compressor runs for 6 minutes and rests for 4 minutes in a 10-minute cycle, it has a 60% duty cycle. Understanding the duty cycle is essential to avoid overworking the compressor, which can lead to overheating and potential malfunction.
Rotary screw compressors are known for their ability to operate with a 100% duty cycle, making them ideal for applications requiring continuous airflow. These compressors are designed to run non-stop without overheating, thanks to their cooling mechanisms, such as oil injection. This capability is particularly beneficial for industrial settings where compressed air is needed for prolonged periods, such as in manufacturing processes, food processing, and pharmaceuticals
Piston compressors, on the other hand, are better suited for applications with a lower duty cycle. They typically have duty cycles ranging from 25% to 75%, meaning they require rest periods to cool down between cycles
These compressors are ideal for tasks that need short, intense bursts of air rather than continuous operation. Applications might include DIY projects, small workshops, or any scenario where the air demand is intermittent.
When selecting an air compressor, it's crucial to consider the duty cycle in relation to your specific air demand. For continuous or high-volume air needs, a rotary screw compressor with a 100% duty cycle is more suitable. For intermittent use or lower air volume requirements, a piston compressor with a lower duty cycle may be adequate.
When it comes to selecting air compressors, noise levels and air quality are significant considerations, especially for indoor environments. Atlas Copco's rotary screw compressors are engineered to address these concerns effectively.
Atlas Copco's rotary screw compressors are designed to operate quietly, making them suitable for indoor use where noise is a concern. For instance, Atlas Copco's VSD+ compressors can operate at noise levels as low as 62 decibels, which is quieter than the average conversation.
This low noise level is achieved through several design features:
Innovative VSD+ Technology: The VSD+ compressors are equipped with a full or partial enclosure that absorbs sound, reducing noise levels to below 60 dB, and can be placed next to production lines without disturbing operators.
Reduced Mechanical Noise: The absence of coupling or gears between the motor and screw element in these compressors contributes to their quiet operation.
Atlas Copco compressors are not only quiet but also ensure high air quality, which is crucial for many applications. The GA range of oil-injected rotary screw compressors offers various versions to meet different air quality standards, including fixed-speed, dual-speed, and variable speed drive versions
The company is the world’s best integrated fixed speed screw air compressor supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
Key features that contribute to air quality include:
Oil Injection: The oil-injected screw compressors require oil for several functions, including cooling, lubrication, and noise dissipation, which contributes to the overall air quality
Advanced Air Treatment: Atlas Copco offers advanced air treatment technologies, such as refrigeration drying for low dew point needs and desiccant drying for even lower dew points, ensuring the air meets specific purity classes.
The combination of low noise levels and high air quality makes Atlas Copco's rotary screw compressors particularly beneficial for indoor environments. They can be placed closer to workspaces without causing noise disruption or compromising air purity, which is essential for applications in medical facilities, laboratories, and food processing industries.
Atlas Copco provides detailed information about the noise levels of their compressors, allowing customers to make informed decisions based on their specific requirements. For example, the G/GX range offers a quieter alternative to piston compressors, with up to a 13% reduction in noise levels.
You should use oil-free compressed air in any application where there is direct contact with food. But there are many other food packaging and handling applications where an oil-lubricated compressor would be the best power source.
Over the years, we have found that certain false assumptions about compressors and compressed air systems persist and grow even stronger. Some have a basis in fact, but others are flat-out wrong, no matter how you slice it. A few are even dangerous.
So we’d like to take this opportunity to debunk a few more common ones. And explain what you need to know in each instance.
Pressure is important, but it’s not the only thing. Any application served by your compressed air system needs two things to accomplish its task.
First, it needs enough pressure to accomplish its task. That’s the PSIG.
And second, it needs enough flow, measured in CFM, to deliver the energy you need for the tool to accomplish its task at that pressure.
If there’s not enough pressure, the tool won’t work. But if there’s too much, it probably will break.
And, with flow, if you don’t have enough (CFM), it will cause a drop in pressure, which means the task will go more slowly, potentially damaging the work product.
So, it’s true, you do have to pay attention to pressure. But flow is just as important.
Variable speed drives (VSDs) are like your car’s cruise control. They adjust your compressor’s power levels, varying the RPM of the compressor to match the required flow of the system—trying to keep pressure constant. In that way, they are helpful at partial loads.
But they are sensitive to heat, moisture, dirty environments and conductive materials. As a result, we sometimes do not recommend VSDs because the environmental conditions are too harsh to ensure trouble-free operation. Flow control is an asset, with or without VSDs.
We have seen too many companies use their compressed air in breathing equipment. That’s a bad idea. Here’s why: intake air can include environmental contaminants and pollutants like carbon monoxide, which are then concentrated during the compression process. That’s a bad mix.
As a result, we encourage companies to ensure proper airflow and ventilation in all workplaces. And we always tell our customers not to use compressed air from their air compressor system without the proper purification equipment for breathing equipment like hoods and masks. It’s also important to tell your people not to use compressed air to clean clothing or skin.
Like most equipment manufacturers, we’re always taking advantage of the latest materials and technologies to enhance the performance of our products. The same is true of our parts.
Our compressors and parts have been engineered as an integrated system, with all the elements working together to optimize performance and productivity. Even the slightest variations could reduce life expectancy, reliability, energy consumption and air quality.
Almost all compressor manufacturers, including Kaishan, require that you use their original OEM parts to maintain your warranty eligibility and ensure that your air compressor system achieves the expected performance level. And safety.
Advocates often pressure food and beverage companies to use oil-free compressors. They claim that oil-free models provide better air quality and are required by FDA regulations.
But that’s overkill, as far as we are concerned. Not all food and beverage applications need oil-free air. The key word here is “all.”
Yes, your compressed air needs to be oil-free anywhere it comes in direct contact with food (as opposed to incidental contact like packaging and material handling). That’s in the regulations, and we have no quarrel with that.
But using an oil-free compressor is no guarantee that the air itself will not contain oil, which can enter the compressor in a number of ways, especially in the intake air. So even oil-free compressors need to have cleanup equipment to remove oil. And, as mentioned, there are many other incidental contact applications, from packaging to material handling, where compressed air is the best power source. Use of food-grade lubricants eliminates hazards to end-use products.
It may seem odd for a screw compressor manufacturer to tell a customer they don’t need a screw compressor. But there are occasions when another technology would be a better fit. The prime example is a small automotive shop where a reciprocating compressor would be a more cost-effective choice because of the low initial cost. However, we often find that the customers ask for screw compressors because their existing recips are too noisy.
And at the other end of the spectrum, there are some situations requiring so much capacity that a centrifugal air compressor is the most cost-effective choice.
If you’re not getting the pressure you need at a remote application like a framing mailer, you probably can’t solve the problem by boosting the pressure output from your air compressor.
They tell us they’re not getting enough pressure at one of their critical applications like a disc sander, framing nailer or tire inflater. So they bump up the pressure at their compressor. And it doesn’t work. Pressure actually drops. How can that be?
The answer is that most air compressors are designed to deliver a fixed amount of output, usually expressed as a set flow number (e.g., 100 CFM) at a set pressure (e.g., 100 PSIG). The two are inversely related, however—when you increase the pressure, you decrease the flow. And vice versa.
Suppose you’re at 100 PSIG and bump it up to 120, hoping to get some extra pressure out in your system. Unfortunately, that inverse relationship between pressure and flow results in less flow.
Plus, all those tiny leaks throughout your compressed air system are under more pressure. So they begin to leak even more air, reducing both flow and pressure. That’s called “artificial demand,” with higher pressure causing more CFM to flow through the same-sized leak. So rather than fixing the problem, your "solution" just made things worse, delivering less air volume at the end of the line. And probably lower pressure.
It may seem counterintuitive, but the best way to get more pressure at the end of the line is to lower the pressure at the air compressor. That will boost the CFM and deliver more airflow to the tool at the desired pressure.
We also encourage looping the main header to keep pressure balanced in the system. If a process is not getting enough air, it's usually the process at the end of a straight run where the problem is occurring. Looping makes the compressed air system bidirectional, providing additional flow. That’s important if there's a specific process that uses a lot of CFM that would bring down the pressure in a straight pipe run.
And, when you have time, you’ll want to fix those leaks. For more information on fixing links, see our blog post, “How to Find and Stop Air Leaks.”
There are a lot of myths surrounding air compressors and compressed air systems. But your rotary screw air compressor is critical to the operation of your compressed air system and all the processes that rely on that system. So you don’t want to let misleading or inaccurate information result in poor performance, downtime or safety issues. If you have questions about some of the myths or questionable information you hear about your air compressor system, go to the best information source. Get in touch with the experts at Kaishan. Contact us today.
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