Rotary Screw Air Compressors

A rotary screw compressor is a type of air compressor that uses two interlocking helical screws, known as rotors, to compress air. As the rotors turn, air is drawn in and progressively compressed as it moves along the length of the screws before being discharged at the required working pressure. Unlike piston compressors, which compress air in pulses, a screw compressor delivers a smooth and continuous flow of compressed air, making it the preferred choice for industrial applications where a consistent and reliable supply is essential.

Rotary screw compressors are designed for continuous duty use, meaning they can run around the clock without the need for rest periods or cool-down cycles. This makes them significantly more suited to high-demand environments than reciprocating alternatives. They are also considerably quieter, more energy efficient, and easier to maintain, with longer service intervals and lower long-term running costs. A direct drive compressor, such as those found across the NUAIR Orion range, eliminates the need for belts or gears by connecting the motor directly to the air-end in a 1:1 ratio, maximising efficiency and minimising mechanical wear. For applications requiring clean, dry air, many models are also available as a rotary screw compressor with dryer, integrating refrigerated drying technology into a single compact unit.

Selecting the right rotary screw compressor for your application comes down to a few key considerations. Assessing each of these before deciding will ensure investing in a machine that meets demand reliably and cost-effectively for years to come.

• Free Air Delivery: The most important factor is ensuring the compressor can supply enough air to meet the combined demand of all tools and equipment connected to it. Free air delivery is measured in litres per minute (l/min) or cubic feet per minute (CFM), and your chosen compressor should comfortably exceed your total air demand to avoid pressure drop during peak usage. These compressors range from 9.2 CFM to 37.1 CFM.
• Working Pressure: Check the maximum working pressure required by your tools and equipment, measured in bar or PSI. All models in the NUAIR Orion range operate at up to 10 bar (145 PSI), which is sufficient for the vast majority of industrial applications.
• Single Phase or Three Phase: Smaller installations without access to a three-phase power supply should consider the NUAIR MiniOrion, which runs on a standard 230V single-phase 16A supply. For larger industrial applications with three-phase power available, the NUAIR Orion range offers significantly higher output and is available in 4 kW, 5.5 kW, and 7.5 kW configurations.
• Dryer Requirement: If the application involves painting, sandblasting, food processing, or any process where moisture in the air supply could cause damage or contamination, a rotary screw compressor with dryer is strongly recommended. Integrated dryer models are available across both the MiniOrion and Orion ranges, combining the compressor and refrigerated dryer into a single convenient unit.
• Duty Cycle and Environment: All NUAIR screw compressors are rated for continuous duty, making them suitable for round-the-clock operation. Consider the available space when selecting a model, and ensure adequate ventilation is provided to maintain efficient operation.

• Check and change the compressor oil regularly: Oil is crucial for use with any rotary screw compressor, lubricating the air-end and protecting internal components from wear. Regular oil changes using the correct grade of compressor oil are essential to maintaining performance and preventing costly damage.
• Replace filters on schedule: Air filters, oil filters, and separator filters all play a critical role in keeping your compressor running cleanly and efficiently. Allowing filters to become blocked restricts airflow, increases energy consumption, and can cause premature wear.
• Monitor the controller display: The electronic controller on NUAIR screw compressors provides real-time information on operating pressure, oil temperature, running hours, and maintenance intervals. Checking the display regularly allows you to identify any abnormal readings early and act before a minor issue becomes a significant problem.
• Keep the unit clean and well ventilated: Rotary screw compressors generate heat during operation and require adequate ventilation to maintain efficient performance. Ensure the area around the compressor is kept clear of dust and debris, and that air can circulate freely around the unit at all times.
• Drain condensate regularly: Moisture can accumulate in the receiver tank over time. Draining the condensate regularly prevents water build-up, which can cause corrosion and reduce the quality of the compressed air supply. If your application is sensitive to moisture, consider upgrading to a model with an integrated refrigerated dryer.

• Materials:
  • Body: 316L Stainless Steel
  • Seal: Ethylene Propylene Diene Monomer (EPDM)

  • Alternative Seal: Fluoroelastomer (FKM)

• Pressure Rating: Up to 16 bar (240 PSI)

• Temperature Range: -35°C to +85°C

• Sizes Available: 15mm to 108mm

• Press Profile: M

• Approvals:
  • WRAS approved

  • DVGW approved

• Pipe Compatibility: PremPress Stainless Steel Press Fit Pipe

• 316L Stainless Steel Construction: Delivers excellent corrosion resistance and ensures a long, reliable service life even in demanding environments.
• 16 Bar Pressure Rating: Suitable for high-performance building services and a wide range of process applications.
• WRAS and DVGW Approved: Supports confidence for use in potable water and approved water system installations.
• M-profile Compatibility: Designed to work with widely used press tools for easy integration on-site.
• Flame-free Installation: Removes the need for hot works, improving safety and simplifying site compliance.
• Failsafe Leak Detection: Unpressed joints are designed to visibly leak during testing for added installation security.
• Broad Size Range: Covers both small branch lines and larger distribution pipework requirements.
• Fast Installation: Significantly reduces labour time compared with traditional jointing methods such as soldering or compression.

When selecting a press fit system, the material plays a major role in performance, lifespan and suitability for the application. Below is a comparison of common alternatives and where Stainless Steel offers a clear advantage.

• Copper:
  • Strenths: Copper is a well-established material in plumbing and heating systems. It is easy to work with, widely available, and has natural antimicrobial properties, which make it suitable for potable water. It also performs well across a typical temperature range found in domestic and light commercial installations.
  • Weaknesses: Copper can be more susceptible to corrosion in certain water conditions, particularly where water chemistry is aggressive or inconsistent. It is also softer than Stainless Steel, meaning it is more prone to damage, deformation, and wear over time, especially in exposed or industrial environments. Material cost can also be volatile.
  • Comparison: Stainless Steel offers significantly greater mechanical strength and durability, making it more suitable for demanding installations. It provides superior corrosion resistance across a wider range of conditions, particularly in commercial, industrial, or exposed environments. For long-term reliability and reduced maintenance, Stainless Steel is often the stronger choice.

• Carbon Steel:
  • Strengths: Carbon Steel press systems are commonly used in closed heating and chilled water systems. They are typically more cost-effective upfront than Stainless Steel and perform well in controlled environments where oxygen exposure and moisture are limited.
  • Weaknesses: Carbon Steel is inherently more vulnerable to corrosion, particularly in open systems or where oxygen ingress is present. It is not suitable for potable water applications and generally requires more controlled conditions to prevent degradation over time.
  • Comparison: Stainless Steel eliminates many of the corrosion concerns associated with Carbon Steel, making it suitable for both open and closed systems, including potable water. It provides a longer service life with less risk of internal or external corrosion, reducing the need for system treatment and ongoing maintenance.

• Multilayer Systems:
  • Strengths: Multilayer pipe systems combine plastic with an aluminium core, offering flexibility, lightweight handling, and ease of installation. They are commonly used in domestic and light commercial plumbing and heating systems, particularly where speed and simplicity are key.
  • Weaknesses: These systems have lower mechanical strength compared to metal pipework and can be more susceptible to damage from impact, UV exposure, or improper installation. Temperature and pressure limits are generally lower, and they may not be suitable for more demanding industrial or plant room environments.
  • Comparison: Stainless Steel provides a far more robust and durable solution, particularly in commercial and industrial settings. It offers higher pressure and temperature capabilities, greater resistance to physical damage, and a more professional finish for exposed installations. Where long-term performance and strength are critical, Stainless Steel is the more dependable option.

Correct pipe preparation and installation are essential to achieving a secure, long-lasting press fit connection. While the process is straightforward, attention to detail at each stage ensures system reliability, protects the internal seal, and maintains the integrity of the joint.

1. Cutting and Preparing the Pipe:

• Stainless Steel Press Fit Pipe must be cut cleanly and square to ensure proper alignment within the fitting. This is typically done using a compatible tube cutter or powered cutting tool designed for precision work. The goal is to achieve a smooth, even cut without distorting the pipe end.

• Once cut, the pipe must be thoroughly deburred both internally and externally using a deburrer or reaming pen. Any sharp edges or residual swarf can damage the internal sealing ring during insertion, potentially leading to leaks or premature failure. A clean, smooth pipe end allows the fitting to seat correctly and ensures the seal performs as intended.

• It is also important to keep the pipe end free from dirt, grease or debris before assembly. Contamination can interfere with the sealing surface and compromise joint performance. Proper preparation is not just best practice; it is a critical step in ensuring a reliable connection.

2. Marking Insertion Depth:

• Before assembling the joint, it is important to mark the correct insertion depth on the pipe clearly with a suitable marker. This should be done using the manufacturer’s depth guide or fitting specification to ensure accuracy. The mark provides a simple yet critical visual check, confirming that the pipe has been fully inserted into the fitting before pressing.

• Without this step, there is a risk that the pipe may not be pushed in far enough, which can compromise both the mechanical grip and the effectiveness of the internal seal. A clearly visible insertion mark helps installers quickly verify correct positioning during installation and inspection, reducing the likelihood of joint failure.

3. Inserting the Pipe:

• Once prepared and marked, the pipe should be inserted fully into the fitting until it reaches the marked depth. This ensures that the pipe is correctly seated within the fitting, surpassing the sealing element.

• During insertion, it is important to apply steady, even pressure and avoid twisting or forcing the pipe, as this could damage the internal seal. A properly inserted pipe will sit securely within the fitting, ready for pressing, with the insertion mark aligning precisely at the edge of the fitting.

4. Press the Fitting:

• With the pipe correctly inserted, a compatible press tool fitted with the correct M-profile jaw should be positioned around the fitting. It is essential that the correct jaw size and profile are used, as this ensures the fitting is pressed to the required specification.

• When the tool is activated, it compresses the fitting around the pipe, permanently deforming the Stainless Steel to create a strong mechanical connection. At the same time, the internal seal is compressed to form a reliable, watertight joint. This single action delivers both strength and sealing performance, making press fit systems fast and consistent to install.

4. Test the System:

• After installation, the system should be pressure tested in accordance with site requirements or relevant standards. This step is essential to confirm that all joints have been correctly installed and are performing as expected.

• PremPress fittings are designed with a failsafe feature, where any unpressed joints will allow water to pass during testing. This makes it easier to identify missed connections before the system is put into service, providing an additional level of confidence in the overall installation.

• A thorough test ensures the system is safe, secure, and ready for operation, helping to prevent issues once the installation is complete.

If you are looking for a cost-effective Stainless Steel Press Fit system that still delivers professional-grade performance, PremPress offers an excellent balance of speed, strength and corrosion resistance. With 316L stainless steel pipe and fittings, M-profile connections, WRAS approval for suitable water applications, and sizes from 15mm to 108mm, it is a smart choice for potable water, heating, cooling and process pipework where reliability and installation efficiency both matter.