Screw vs Lobe Blower Technology: Which One’s Better?
While low-pressure blowers are not as widely recognized as medium-pressure ones (also called air compressor systems), they are essential in low-pressure applications for several industries. Aquaculture, cement plants, flue gas desulfurization, food and beverage, non-woven textiles, and pneumatic conveying, to name a few.
Several facilities use typical medium-pressure air compressor systems that produce 7 to 8 bars and bring their pressure down to 2 to 3 bars for low-pressure applications, which results in excessive energy consumption and energy bills.
On the other hand, low-pressure blowers typically produce a pressure between 0.3 and 4 bar – making them an excellent fit for low-pressure applications.
The two most popular technologies used in blowers are screw and lobe. Even though lobe technology produced great results when it was first discovered by the Roots brothers in 1854, it failed to stand the time due to less or no improvements since its inception.
In this blog, we will discuss lobe (roots) and screw technology in low-pressure blowers and find out why the latter is a better solution for low-pressure industrial applications.
Let’s get started!
How Does A Lobe Or Roots Low-Pressure Blower Work?
A lobe or "Roots" blower is a low-pressure blower that uses isochoric compression.
Isochoric compression means that the air volume in the compression chamber remains constant. The lobe rotors in the chamber rotate, which decreases the volume of the chamber and causes compression. The compression occurs externally against full counter-pressure due to incoming air from a connected pipeline.
External compression results in low efficiency and high noise levels, which limits the use of lobe technology to low-pressure applications in a single stage. Two-stage and three-stage versions are available, but they are not as common because of the low efficiency and high noise levels.
Even though the lobe or root blowers are designed for low-pressure applications, their low efficiency and high noise levels don’t make them an idle choice. Not in today’s industrial sector, where costs are crucial, and keeping them efficient is even more crucial.
Pressure/Volume diagram of a lobe blower
4-1: Air intake – volume increase to Vs
1-2: Compression by back-flow from receiver to blower
2-3: Air delivery from blower to receiver
Rectangle area 1-2-3-4 represents the compression work Wt.
Power consumption is proportional with blue area 1-2-3-4
Pressure/Volume diagram of a screw blower
4 -1: Suction – air enters the compression chamber
1-2: Internal compression – as the rotors move towards each other, the air volume decreases
2-3: Discharge – air is pushed out into the pipeline
How Does A Screw Blower Work?
Unlike lobe or root blowers, the screw blower functions on the principle of isentropic compression.
It follows a similar mechanism to rotary screw compressors. The screw blower comes with a male and female rotor that rotates in the opposite direction and decreases the volume between them to generate compressed air.
1-2: Internal compression in screw blower; 2-3: Air delivery from screw blower to receiver
What Makes Screw Blowers A Better Choice Than Lobe Blowers?
Air blowers have the potential to contribute up to 80% in energy consumption and costs throughout their lifecycle.
The internal compression mechanism of a screw blower is more efficient as compared to the functioning of lobe air blowers. Screw blowers consume less energy as minimal amount of heat is produced.
In short, screw blowers generate more efficiency than lobe ones when run at the same pressure.
Let us explain this using an example:
- For ambient temperature of 35 deg C
- Rated flow: 2000 m3/hr
- Pressure: 0.7 bar(g)
Considering the above values, the energy consumed by the lobe or roots blower would be 61 kW with an air discharge temperature of 125 degrees Celsius. However, a screw blower will produce 43 kW of energy with an air discharge temperature of 94 degrees Celsius.
On average, rotary screw blowers contribute to 35 to 40 percent electricity savings annually, making them, hands down, better blowers for low-pressure industrial applications. The pressure requirement is directly related to the potential savings and inversely associated with the total cost of ownership.
The technology used in rotary screw air blowers is perfect for variable speed configuration as it keeps the energy level constant at varying operating points resulting in consumption and cost efficiency.
In a nutshell, rotary screw air blowers are great energy savers. They produce less heat, making them both cost- and energy efficient – making them a perfect choice for low-pressure industrial applications.
Become Efficient With Atlas Copco’s ZS Screw Blowers
Atlas Copco is a premium air compressor manufacturer and supplier. Its comprehensive range of products comprises air compressors, air blowers and other related accessories.
If you are looking for higher efficiency and lower costs for your low-pressure industrial usage or if you are tired of paying massive due to the continuous use of lobe blowers and looking for a replacement, you should consider Atlas Copco’s ZS screw blowers that offer robust air blower solutions of up to 1.5 bar. The ZS screw blowers come in compact designs that can be installed and fitted anywhere.The same technology is available for higher discharge pressures of up to 4 bar in water and air cooled - ZA or ZE screw blowers.
Air Blowers from Atlas Copco are reliable to operate in harsh conditions of altitudes and temperatures of 50 degC.
Minimizes energy consumption and maximizes the savings and uptime with Atlas Copco’s ZS screw blowers today. Click here to find the brochure on different models of screw blowers.
