Basics on rotary screw compressor

A rotary screw compressor compresses air by using two meshing helical screws or rotors. The air is drawn in through a filter and an open inlet valve to the compressor element. As the rotors rotate, the volume of the air is reduced, resulting in an increase in pressure.

The compressed air then flows into a separator tank where most of the oil is separated out in oil-lubricated screw compressors. The separated oil can be reintroduced into the air-end or go through an oil cooler depending on its temperature.

In contrast, oil-free screw compressors use gears to control the timing between the two rotors, and there is no oil to lubricate, cool, or seal the chamber. This makes them less efficient and results in a lower maximum pressure compared to oil-lubricated compressors.

Oil-free compressors are useful when high air quality is required, such as in the pharmaceutical or food and beverage industries.

The main components of a rotary screw compressor include:

• Compressor element: The compressor element consists of two interlocking helical rotors that compress the intake air.
• Drive motor: The drive motor powers the compressor element.
• Air/oil separator: The air/oil separator separates most of the oil from the compressed air using centrifugal force.
• Oil filter: The oil filter removes impurities from the oil.
• Oil cooler: The oil cooler cools the oil before it enters the compressor element.
• Thermostatic bypass valve: The thermostatic bypass valve allows oil to enter the compressor element when the valve opens at a specific temperature.
• Oil stop valve: The oil stop valve prevents flooding of the compressor element via the oil.

Rotary screw compressors have several advantages over piston compressors, including:

• Higher capacity: Rotary screw compressors offer a constant air flow and higher capacity, making them ideal for industrial applications.
• Continuous running: Unlike piston compressors, rotary screw compressors do not have valve systems, allowing them to operate at high air flow rates with a higher duty cycle which enables continuous running.
• Lower maintenance: Rotary screw compressors have fewer moving parts than piston compressors, resulting in lower maintenance requirements.
• Quieter operation: Rotary screw compressors operate more quietly than piston compressors, making them ideal for noise-sensitive environments.

However, rotary screw compressors also have some limitations, including:

• Higher initial cost:  Rotary screw compressors are more expensive than piston compressors, since they have a longer lifespan and produce more air.
• Oil-lubricated compressors require regular oil changes and maintenance. Despite the new design made the maintenance easier, rotary screw compressors are still a complex system and the help of a skilled technician is still highly valuable.

Rotary screw compressors require regular maintenance to ensure optimal performance and longevity. Some maintenance tasks include:

• Regular oil changes and filter replacements for oil-lubricated compressors.

• Cleaning or replacing air filters.

• Checking and adjusting belts and pulleys.

• Inspecting and cleaning coolers and heat exchangers.

• Checking and adjusting the thermostatic bypass valve.

Proper maintenance can help prevent breakdowns, reduce energy consumption, and extend the life of the compressor. It is also important to choose the right size and type of compressor for your application to maximize efficiency and reduce energy costs and carbon footprint.