Low pressure Permannent Magnetic VSD screw air compressor LB serie

Low-Pressure Screw Air Compressors for High Air Volume

The LB series low-pressure screw air compressors are designed for applications where standard pressure of 7–10 bar is not required. Instead of generating compressed air at a higher pressure and reducing it afterwards, the compressor operates directly within the required range of 2 to 5 bar.

This is particularly important for processes with high and continuous air consumption. A correctly selected low-pressure compressor can reduce energy losses associated with generating unnecessarily high pressure.
The LB series combines a screw airend, permanent magnet motor and VSD control. Motor speed is adjusted according to current load, allowing compressor output to follow the demand of the production process more closely.

Models with Air Delivery from 12 to 47.4 m³/min

The series includes five main models:

• SCR420LB – 12 m³/min;
• SCR530LB – 15 m³/min;
• SCR830LB – 21.5 m³/min;
• SCR950LB – 28.8 m³/min;
• SCR1500LB – 47.4 m³/min.

The SCR420LB and SCR530LB are suitable for systems with relatively lower but continuous air demand. The SCR830LB and SCR950LB can supply larger process lines and pneumatic conveying installations. The SCR1500LB is intended for processes with very high consumption and delivers 47.4 m³/min.

For these models, air delivery is specified for the compressor, while the required motor power changes according to working pressure.

Working Pressure from 2 to 5 Bar

LB compressors can operate at pressures from 2 to 5 bar. The configurations in the technical tables are divided into:

• operation at 2–3 bar;
• operation at 4 bar;
• operation at 5 bar.

Required motor power increases at higher pressure. For example, the SCR830LB uses 63 kW at 2–3 bar, 75 kW at 4 bar and 90 kW at 5 bar.
This demonstrates why the compressor should not be set to a higher pressure than the process actually requires. Even a relatively small increase in pressure can significantly raise electricity consumption when air delivery is high and continuous.

Power Ratings from 37 to 185 kW

The LB series covers power ratings from 37 to 185 kW. The exact value depends on both the compressor model and the selected working pressure.
The smallest SCR420LB requires 37 kW at 2–3 bar and 55 kW at 4–5 bar. The largest SCR1500LB operates with 132 kW at 2–3 bar, 160 kW at 4 bar and 185 kW at 5 bar.

Selection should therefore consider the following factors together:

• required air delivery;
• minimum sufficient pressure;
• load profile;
• operating hours;
• total energy consumption.

Advantages of a Low-Pressure Screw Air Compressor

The main advantage is the production of high air volume at a pressure matched directly to the industrial process.

This can provide:

• lower required power compared with compressing air to standard high pressure;
• reduced losses from subsequent pressure reduction;
  stable air flow;
• suitability for continuous-duty operation;
• adjustment to fluctuating demand through VSD control;
• more stable system pressure;
• smoother motor starting.

Actual performance depends on correct sizing, the condition of the pipeline network and accurate working pressure settings.

Low Pressure Instead of a Standard 7–10 Bar Compressor

For a process requiring 3 bar, using a standard compressor operating at 7 or 8 bar and then reducing the pressure can create unnecessary energy consumption.

A low-pressure compressor generates air directly at the pressure required by the process. This makes it suitable for large consumers that do not need the higher pressure commonly used by standard pneumatic tools and machinery.

Correct selection should account for pressure losses through the pipeline and the minimum pressure required at the final point of use.

Applications of LB Low-Pressure Compressors

Pneumatic Conveying

Low-pressure compressed air can be used to move powdered and granular materials through pipeline systems. Typical examples include cement, flour, plastic granules and other bulk materials.

Cement Production

Cement plants may require large quantities of air for conveying, aeration and various production processes. The LB series provides high air delivery at pressures up to 5 bar.

Textile Manufacturing

Textile processes may require continuous air flow for production machinery, cleaning and material movement. Stable air delivery supports reliable operation.

Processing and Manufacturing Industries

The compressors can be used for aeration, blowing, cooling, drying and other processes requiring high air delivery at low pressure.

DN80, DN100 and DN150 Outlet Sizes

The SCR420LB and SCR530LB models use DN80 outlets. The SCR830LB and SCR950LB use DN100, while the SCR1500LB is equipped with a DN150 outlet.

Pipeline size must be selected according to air delivery, pipe length and the permitted pressure drop. Undersized pipework is particularly critical in a low-pressure system because even a fraction of one bar in losses can have a significant effect on process performance.

How to Select the Correct Low-Pressure Compressor

Determine the Actual Required Air Delivery
The air consumption of the industrial process should be measured or calculated. For continuous-duty applications, actual operating values should be used rather than only nominal equipment data.

Determine the Minimum Sufficient Pressure
Select the lowest pressure at which the process operates reliably. Only actual pipeline and equipment pressure losses should be added.

Check Motor Power at the Required Pressure
The same compressor model may require different motor power at 3, 4 or 5 bar. Models should therefore not be compared by air delivery alone.

Analyse the Operating Profile
Determine whether demand is constant or variable. With fluctuating load, VSD control can regulate compressor output according to consumption.

Check Space and Installation Conditions
The compressors weigh between 2,400 and 5,300 kg and require a suitable foundation, adequate ventilation, service access and a planned transport route to the installation position.

Designing a Low-Pressure Air System
At high air delivery, correct pipeline design is as important as compressor selection. Pipe diameter, permitted pressure drop, required air storage and air quality requirements must all be established.

Depending on the application, filters, dryers, coolers, air receivers and condensate management equipment may also be required.

Consultation for Selecting an LB Series Compressor
Accurate selection requires information about required air delivery, minimum pressure at the point of use, operating hours, load profile and pipeline characteristics.

Contact our team for technical consultation and assistance in selecting an LB series low-pressure screw air compressor according to the requirements of your production process.

Frequently Asked Questions

What is a low-pressure screw air compressor?

It is a compressor designed to generate a high volume of compressed air at relatively low working pressure. The LB series operates from 2 to 5 bar.

What air delivery does the LB series provide?

The series covers air delivery from 12 to 47.4 m³/min.

Why does the required power change with pressure?

Compressing air to a higher pressure requires more energy. The same model therefore uses more motor power at 4 or 5 bar.

Are these compressors suitable for pneumatic conveying?

Yes. Their high air delivery and low working pressure make them suitable for various pneumatic material conveying systems.

Can a standard 8 bar compressor be used instead?

It may be technically possible in some systems, but generating air at unnecessarily high pressure and reducing it afterwards can be energy-inefficient.

What is the largest model in the series?

The SCR1500LB delivers 47.4 m³/min and uses between 132 and 185 kW depending on working pressure.