Energy efficiency and selection of Atlas Copco ZR/ZT oil-free screw compressor

Atlas Copco ZR/ZT series oil-free screw compressors: a comprehensive interpretation of energy efficiency, purity, and reliability

In industries such as food and beverage, pharmaceuticals, electronics, automotive spraying, and petrochemicals, the quality of compressed air directly affects product safety, process stability, and operating costs. The risks brought by oil pollution - whether it is product scrapping, equipment damage, or brand reputation damage - make 100% oil-free compressed air an uncompromising requirement. Atlas Copco's ZR/ZT series oil-free screw compressor, with its technical accumulation of more than 60 years, ISO 8573-1 CLASS 0 (2010) certification, and integrated frequency conversion (VSD) and drying technology, provides industrial users with a complete solution that gives consideration to both energy efficiency and reliability. This article will provide a comprehensive technical reference for compressed air system engineers from the perspectives of oil-free technology principles, energy efficiency optimization methods, integrated full function design, selection parameters, and engineering applications.

ZR/ZT series positioning and technical foundation

The ZR/ZT series belongs to water lubricated or dry oil-free screw compressors (specifically dry twin-screw, oil-free at the air end). Its core compression element adopts a special rotor profile and sealing structure to ensure that there is no need for any lubricant in the compression chamber, thus eliminating the possibility of oil pollution from the root. This series is divided into:

ZR series: water-cooled type, suitable for fixed installation scenarios with cooling water circulation.

ZT series: air-cooled type, suitable for occasions with water shortage or low dependence on cooling water.

Both offer two driving modes: fixed speed (fixed frequency) and VSD (Variable Speed Drive), and can be configured with Full Feature, which includes an IMD (internal heat regeneration adsorption) dryer for one-stop high-quality compressed air supply.

100% oil-free certification - hard power of CLASS 0

2.1 Industry benchmarks beyond ISO standards

ISO 8573-1 classifies the total oil content (aerosols, liquid oil, oil vapor) in compressed air into levels 0-5, with Class 0 being the most stringent - "specified by equipment users or suppliers and more stringent than Class 1". The ZR/ZT series has been independently tested by T Ü V Germany and has not detected any oil stains in extreme temperature and pressure ranges, becoming one of the first compressor brands in the world to obtain CLASS 0 certification. This means:

Zero pollution risk, no need to worry about the damage of oil pollution to products (such as food, drugs, chips).

Zero downstream equipment pollution, significantly extending the lifespan of dryers, filters, pipelines, and pneumatic components.

Zero compliance risk, meeting regulatory requirements for industries such as food grade (FSSC 22000) and pharmaceutical (GMP).

2.2 Z-sealing technology and efficient rotor coating

ZR/ZT adopts Atlas Copco's patented Z-seal design, forming multi-level barriers at the rotor shaft end to prevent air leakage and absolutely isolate the oil chamber. At the same time, the rotor surface is coated with a high-performance corrosion-resistant coating to ensure long-term operational efficiency without degradation, and is maintained at a constant working temperature with a cooling jacket to extend the lifespan of the components.

Energy Efficiency Optimization System: VSD and System Design

3.1 VSD frequency conversion - average energy saving of 35%

Electricity accounts for over 80% of the total lifecycle cost of compressed air systems. VSD technology controls pressure fluctuations within ± 0.1 bar by matching motor speed in real-time with actual gas demand, avoiding energy waste caused by frequent loading/unloading or venting of fixed frequency machines. According to document data, VSD models can reduce energy consumption by up to 35% and average lifecycle costs by 22%. Its unique advantages include:

No speed window: The speed range covers 30% to 100% of the capacity, and there is no mechanical resonance restriction zone, ensuring stable output at any speed.

Integration of dedicated motor and frequency converter: Both the motor and frequency converter are custom designed by Atlas Copco, with IP55 protection level, able to withstand up to 50 ℃ ambient temperature (standard version 40 ℃), and pass EMC testing without interfering with peripheral equipment.

Low pressure band control: maintains the pipeline pressure within a very narrow bandwidth, further reducing system leakage and ineffective power consumption.

3.2 Efficient Transmission and Cooling System

Even for fixed frequency models, ZR/ZT is equipped with IE3/NEMA Premium high-efficiency motors, coupled with low resistance intake filters, large-sized aftercoolers, and inter stage coolers (water-cooled models use stainless steel tubes and aluminum fins for corrosion resistance and high heat transfer efficiency), as well as labyrinth water separators, making the overall specific power (kW/m ³/min) at the forefront of the industry. The technical parameter table in the document clearly lists the FAD (Free Air Delivery) of each model at working pressures such as 7, 9, and 12 bar, providing precise basis for selection.

Full Feature Integrated Drying - True 'Plug and Play'

Traditional compressed air systems require external post-treatment equipment such as dryers and filters after the compressor, which not only occupies space but also affects the final air source quality due to pipeline pressure drop and secondary pollution of condensed water. The Full Feature configuration integrates the IMD adsorption dryer directly into the compressor. Its working principle is to use the compression heat generated during the compression process (which needs to be discharged) to regenerate the desiccant, without the need for additional electricity or compressed air loss, achieving:

Low energy consumption drying: zero external energy demand and minimal pressure loss.

Constant dew point: can provide dew points at -20 ℃, -40 ℃, or even -70 ℃ pressure according to demand, meeting different process requirements.

Compact design: The standard ZT 110-275 Full Feature model is only about 4-5 meters in length (depending on power), making it suitable for data centers with limited space.

For models that do not have the Full Feature, Atlas Copco also offers matching independent dryers (such as XD, ND, BD, FD series), covering various technologies such as cryogenic, thermal regeneration adsorption, and blast regeneration, making it convenient for users to flexibly configure.

Elektronikon Controller and Intelligent Monitoring

All ZR/ZT models come standard with Elektronikon ™ Intelligent controller, equipped with a 5.7-inch color touch screen, supporting 31 languages. Its main functions include:

Accurate loading/unloading and PID regulation to maintain stable pipeline pressure.

Built in service timer, automatically reminding maintenance intervals (oil filter, air filter, grease, etc.).

Remote communication capability: Connected to the factory LAN through a standard Ethernet port, supporting web access and SMARTLINK cloud platform, enabling remote monitoring, fault warning, and energy efficiency analysis.

Mobile App: Supports iOS/Android, making it easy for operations personnel to check the status of the unit anytime and anywhere.

In addition, the controller can integrate advanced diagnostic functions such as SPM vibration monitoring and PT100/PT1000 winding/bearing temperature detection, providing a data foundation for predictive maintenance.

Key points for engineering selection and deployment

6.1 Interpretation of Selection Parameters

Pages 16-19 of the document provide a detailed performance parameter table, with key fields including:

FAD (l/s, m ³/min, cfm): The actual displacement measured under ISO 1217 Annex C standard conditions (20 ℃, 1 bar absolute pressure, 0% relative humidity) is the core indicator for measuring the gas production capacity of a compressor.

Working pressure (bar (e)): ZR/ZT covers a range of 4-13 bar (e) and needs to be selected based on the maximum required pressure of the gas equipment.

Installed power (kW): Fixed speed models offer multiple levels such as 110~275 kW (50Hz) or 160~315 kW (60Hz); The VSD model provides a pressure flow regulation range.

Noise (dB (A)): All are below 80 dB (A) and equipped with soundproof enclosures, meeting industrial noise standards.

6.2 Selection of Cooling Methods

Water cooling (ZR): Suitable for factories with circulating cooling water. Water cooling has high heat exchange efficiency, is insensitive to ambient temperature, and has a compact unit size.

Air cooling (ZT): Suitable for areas with water shortage or poor water quality, it is necessary to ensure good ventilation in the computer room and reserve sufficient heat dissipation spacing (the document size table provides length, width, and height data).

6.3 Installation and Environmental Requirements

Standard models can adapt to environmental temperatures up to 40 ℃; Optional HAT (High Environmental Temperature) version, up to 50 ℃.

The ground foundation needs to meet the weight of the unit (as low as about 2500 kg, as high as about 6500 kg, depending on the model), and it is recommended to install vibration damping pads.

The intake and exhaust ducts can be designed separately according to the site conditions to allow for the intake or exhaust of hot air to the outside.

6.4 Optional Item Reference

The options listed in the document include:

Anti condensation heater (used for high humidity shutdown state).

Energy recovery device (recovers compressed heat for preheating boiler water or workshop heating).

Various flange standards (ANSI, etc.) facilitate the connection of specific pipelines.

Material certificates and witness performance tests are applicable for engineering project acceptance.

TT/TN and IT network adaptation to meet different distribution systems.

Application scenarios and customer value

7.1 Food and Beverage Industry

Pure air is required for fermentation gas, packaging blowing, and material transportation. CLASS 0 certification ensures no chemical contamination risk, while Full Feature provides stable low dew point to prevent pipeline icing and bacterial growth.

7.2 Automobiles and Painting

If there is a trace of oil mist in the gas used for painting, it can cause defects in the paint surface (shrinkage, fish eyes). ZR/ZT provides absolutely clean compressed air, improving the first pass rate.

7.3 Petrochemical and Power Plants

Instrument gas, control gas, and process gas (such as desulfurization and oxidation) require continuous and uninterrupted operation. The IP55 motor, high reliability design, and long maintenance interval (optional SPM online monitoring) of ZR/ZT ensure an availability rate of ≥ 99%.

Service and full lifecycle support

Atlas Copco's global service network provides:

ToolStart: A one-stop service for installation and debugging.

Preventive maintenance agreement: including regular replacement of oil filters, air filters, rotor bearings (with a lifespan of approximately 60000 to 80000 hours), etc.

Calibration and performance testing: Ensure that the actual operating data is consistent with the design values.

SMARTLINK remote monitoring: online analysis of energy efficiency trends, early warning of component degradation.

Common problems and selection misconceptions

Q1: Are the FADs of ZR and ZT the same?

At the same power, the cooling effect of water-cooled units is slightly better than that of air-cooled units, so the FAD of ZR is usually slightly higher than that of ZT of the same specification (especially in high-temperature environments), but the difference between the two is small and can be selected based on cooling resources.

Q2: Do you need Full Features?

If the dew point requirement at the end is not less than -20 ℃ and you want to simplify the system, Full Feature is an excellent choice. If a lower dew point (such as -70 ℃) is required or an independent dryer has been configured, the standard model can be selected.

Q3: Is VSD suitable for situations with large load fluctuations?

Yes, VSD is designed specifically for fluctuating loads, with significant energy-saving effects. But if the load remains stable at over 95% for a long time, it may be more economical to use a fixed frequency machine for efficient loading and unloading, and it needs to be evaluated in conjunction with specific gas consumption curves.