Single-screw vs. Twin-screw compressors
Compare single and twin compressor systems to understand differences in efficiency, capacity control, and reliability.
The simplicity of a superior design
The Vilter single screw compressor’s strength lies in its robust engineering. It uses a single main rotor and with two opposing gaterotors. This creates a fundamentally balanced and efficient compression process.
Suction gas is drawn in, trapped in the main screw’s helical grooves, and compressed as the gaterotors engage. The compressed gas is then discharged radially. Our exclusive Parallex™ slide system features independent capacity and volume slides, allowing the compressor to precisely match system load and pressure ratio requirements. This dual-slide control optimizes performance across all conditions, a feat of engineering that puts you in complete control.
How single screw compression works
The single screw compressor features a unique balanced design with one main rotor and two opposing gate rotors. This balanced configuration creates equal and opposite forces that cancel each other out, resulting in minimal bearing load, reduced vibration and extended component life.
Efficiency advantages: Performance where it counts most
True efficiency is measured not just at full load, but across the entire operational range. This is where the Vilter single screw compressor establishes its leadership.
- Optimized part-load performance: The Parallex™ slide system adjusts capacity and volume independently, eliminating the over-or-under compression that compromises efficiency in other designs. This delivers significant energy savings, especially in real-world conditions where compressors rarely run at 100% capacity.
- Up to 20% more efficient: At lower capacities (e.g., 25% load), the Vilter single screw can be up to 20% more efficient than a typical twin screw, directly reducing your operational expenditures.
- Control without complexity: Achieve premium part-load efficiency without the capital cost, complex integration, and potential failure points of a VFD. This simplifies your system design and improves its overall reliability.
Reliability & maintenance: Engineered for uptime
Our design philosophy directly addresses the core need of industrial operations: maximizing uptime and minimizing maintenance costs. With a global installed base and decades of proven performance, the Vilter single screw is built for the long run.
Vilter single screw vs. twin-screw: The clear difference
A twin-screw design generates unbalanced radial and axial forces, increasing bearing wear and leading to vibration and limitations on operating pressures. Their part-load efficiency suffers without the added expense and complexity of a VFD. This results in more frequent and costly maintenance, including major overhauls often required every five years.
The Vilter single screw operates with balanced forces, enabling reliable high-pressure performance and extending component life. Its superior part-load efficiency is built-in, not added on. This translates to lower energy bills, reduced maintenance costs, and a more predictable, reliable operation year after year.
In contrast, twin screw compressor slide valves are in-line with each other. This limits the range of motion of the slides. It also requires that the slides do not act independently. The result is that twin screw performance can be less than optimal because the in-line slide valves cannot fully adjust to changing system load and pressure ratio requirements.
Frequently Asked Questions
Do I need a VFD to achieve good part-load efficiency?
The single-screw compressor includes a Parallex slide system – key to part load efficiencies. Capacity & volume slides move independently of each other based on load, eliminating over or under compression and saving motor horsepower. No VFD required.
In a twin-screw compressor style, a variable frequency drive is required, adding complexity and start up costs. Potential penalty on efficiency up to 5%.
How do thrust loads impact each design?
In a single-screw design, a single main rotor with both ends at suction pressure results in extremely low thrust loads. Since the discharge end of the screw is vented to suction, the suction gas pressure is exerted on both ends of the single screw shaft.
In a twin-screw design, the two opposing rotor design creates unbalances high loads on the main screws. Pressure is exerted at the discharge port.
Are radial loads a factor?
In the single-screw design, there are no radial loads on the single rotor. Since compression occurs symmetrically and simultaneously opposite sides of the screw,
the radial forces due to compression are cancelled out.
In the twin-screw design, opposing rotors cause high radial loads. Some twin screws require journal type bearings for high loads, resulting in full time oil pump operation
How do these forces impact bearing loads?
In the single-screw design, the only vertical loads exerted on the main screw bearings are
due to gravity. The first recommended bearing inspection is at 120,000 hours (15 years) resulting in very low maintenance costs and down time during this period.
With twin-screw designs, running higher rpm and higher rotor loads has a direct impact
on the life of all components, including bearings. Typically, costly major overhauls are required every five years.
How serviceable is the compressor?
The single screw is easily serviced in the field.
Twin screw models create challenging service options. Some models are considered “disposable” resulting in additional capital expense.
What kind of warranty does each style offer?
Vilter single screw compressors are backed by one of the industry's strongest warranty programs. For ammonia refrigeration applications, Vilter single screw compressors include a 5-year warranty on internal compressor parts and a 15-year warranty on bearings. Vilter can offer this warranty due to the compressor's inherently balanced design, which minimizes axial and radial bearing loads, reduces vibration, and extends component life.
By comparison, most twin screw compressor designs do not offer a comparable 15-year bearing warranty because their rotor arrangement creates higher bearing loads, resulting in greater wear over time. Warranty terms vary by manufacturer, but they are typically shorter than the Vilter 5/15 warranty program.
