SR Roots Blower

Introduction

Roots blower, also known as a rotary lobe blower or positive displacement (PD) blower, is a reliable and versatile industrial machine designed for moving air and gas at consistent flow rates.

Roots blower operates using the isochoric (external) compression principle. Two lobe-shaped rotors rotate in opposite directions within an enclosed chamber, trapping pockets of air or gas on the intake side and carrying them to the discharge side . Unlike screw compressors, which compress air internally, the Roots blower does not generate internal compression; pressure increase occurs only when the trapped medium is forced into a system with resistance (e.g., a pipe network, water column, or process vessel). This design keeps discharge temperatures relatively low and simplifies the machine's construction.

Roots blowers typically feature no internal oil in the compression chamber, delivering clean, oil-free air or gas. They are commonly air-cooled and designed for continuous, heavy-duty operation across a wide spectrum of demanding applications . With flow and pressure operating as largely independent variables, these blowers maintain a nearly constant flow rate even as discharge pressure fluctuates—a key characteristic that makes them ideal for applications requiring variable pressure conditions.

Working Principle

The operating principle of a Roots blower is based on positive displacement and external compression:

• Intake: As the twin rotors (typically tri-lobe or bi-lobe designs) rotate, they create expanding volumes at the inlet port, drawing air or gas into the chambers.
• Trapping: The rotors seal against each other and the chamber wall, trapping a fixed volume of medium in the pockets between the lobes.
• Displacement: The trapped volume is carried from the inlet side to the outlet side as the rotors continue to rotate.
• Compression: When the rotor lobes pass the outlet port opening, the trapped medium is pushed into the discharge system, where compression occurs against the system backpressure .
• Key Characteristic: Since compression happens externally (against system resistance) rather than inside the blower, the discharge temperature remains lower than in internally compressed machines. This makes Roots blowers suitable for applications where high temperatures are undesirable.
• Lobe Design Evolution: Early bi-lobe designs produced significant pulsation and noise. Modern tri-lobe impellers, designed with advanced aerodynamic theory, reduce pressure pulsations and noise levels while improving efficiency, making them the industry standard for most applications.

Applications

Roots blowers serve a vast range of industries and processes where reliable, oil-free, and pulse-free air or gas movement is essential .

• Water & Wastewater Treatment-Aeration (activated sludge), membrane cleaning, effluent treatment.
• Pneumatic Conveying-Transport of cement, flour, plastics, grains, and other bulk materials.
• Chemical & Petrochemical-Gas handling (steam, nitrogen, hydrogen, hydrocarbons), chemical vapor deposition, process gas transfer
• Cement & Power-Kiln charging, blending, combustion air, ash handling.
• Oil & Gas-Vapor recovery, gas boosting, wellhead gas compression
• Mining & Metals    Steel degassing (high vacuum boosters), dust collection, mine ventilation.
• Food & Beverage-Product drying, pneumatic conveying of ingredients, packaging.
• Pulp & Paper-Vacuum filtration, paper drying, dewatering
• Semiconductor & Electronics-Vacuum processes (CVD, PVD, etching), load-lock vacuum, LED manufacturing.
• Vacuum Trucks-Truck-mounted blowers for industrial vacuum and hydro-excavation services.

Features

Constant, Pulse-Free Flow
Roots blowers deliver a steady, volumetric flow rate that remains largely unaffected by changes in discharge pressure .
Advanced lobe designs (tri-lobe with helical profiles) minimize flow pulsation for smoother operation .

Oil-Free Air/Gas Delivery
With no oil in the compression chamber, these blowers provide clean, uncontaminated air—critical for food, pharmaceutical, and sensitive chemical processes .
Bearings and gears are lubricated externally via splash or forced-feed oil systems, with labyrinth seals preventing oil migration into the gas stream .

Durable Construction for Continuous Duty
Built from robust materials: cast iron casings, alloy steel timing gears, and ductile iron or cast iron impellers .
Oversized anti-friction bearings ensure long service life and resistance to belt pull forces .
Dual Splash Lubrication (DSL) extends oil capacity and enhances reliability for critical applications .

Low Noise & Vibration
WHISPAIR™ technology reduces pressure pulsation and noise by 3–5 dBA compared to conventional blowers .
Tri-lobe impeller designs inherently reduce noise and vibration levels .
Acoustic enclosures are available for further noise attenuation (up to 22 dBA free-field reduction) .

Flexible Installation Options
Detachable steel mounting feet allow the drive shaft to be positioned in any of four orientations: top, bottom, left, or right—simplifying integration into existing systems .
Available in bare shaft or packaged configurations.

High Efficiency & Energy Savings
Modern designs incorporate advanced aerodynamic impeller profiles and internal return channels to optimize efficiency and reduce energy consumption .
Lower operating temperatures contribute to extended component life and reduced cooling requirements.

Specifications

• Flow Rate-Up to 120,000 m³/h (70,000 cfm) for large rotary models; small units up to 10,000 m³/h
• Discharge Pressure-Up to 35 psig (2.4 bar) for large models; standard units to 15 psig
• Vacuum Capability-Up to 28" Hg (949 mbar)
• Lobe Configuration-Bi-lobe (traditional) or Tri-lobe (modern, lower noise)
• Cooling Type-Air-cooled (standard); special designs for higher temperatures
• Drive Options-Direct coupling or belt & pulley drive
• Mounting-Bareshaft or standard packaged unit with motor, filters, silencers, safety valves

Why Choose Our Roots Blowers?

Our Roots blowers combine of proven engineering heritage with continuous innovation. Whether you need a compact unit for a mobile vacuum truck or a massive installation for a steel mill or wastewater treatment plant, we offer tailored solutions backed by extensive process expertise.

Key difference

• Wide product portfolio: From small bare shaft blowers to custom-packaged large units covering the full performance envelope .
• Advanced noise reduction: WHISPAIR™ technology and optional acoustic enclosures for compliance with occupational and environmental noise regulations .
• Dual Splash Lubrication (DSL): Enhanced oil capacity and reliability for continuous, high-duty applications .
• Flexible mounting options: Four drive shaft positions for easy integration into any system layout .
• Comprehensive support: Process sizing, installation guidance, aftermarket spares, and expert technical assistance.
• Contact our application engineering team today to specify the right Roots blower for your process requirements.