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The Duragas Series Overview

Roots Systems manufactures its own compressors – the Duragas series – for handling process gases.

The Duragas series is designed and built for process applications in a wide variety of sizes, materials and sealing arrangements suitable for a wide range of gases, including corrosive, flammable, radioactive and toxic.

Two-stage Duragas Compressor (Tandem Arrangement)

Duragas machines can be designed for low-temperature (‘cryogenic’) applications as well as high.

Oil Free

Our Duragas machines are splash lubricated as standard but include a wide ‘interspace’ between the inner gas seals and the bearing lube oil seals. This acts as a catch pot, preventing lube oil from migrating into the process gas stream.

API Standard 619

Roots Systems is one of the few manufacturers of rotary-lobe blowers in the world that comply with API Standard 619, making our Duragas series the first choice for the petrochemical, oil and gas industries, both onshore and offshore.

Wide Flow Range

The Duragas series covers a range of flows from 5 to 50,000 m3/h (3 to 30,000 cfm).

High Vacuums

Duragas machines can operate at inlet pressures down to a fraction of a millibar (a fraction of a torr) absolute.

High Pressures

Duragas machines can operate at inlet pressures over 150 bar (2175 psi).

High Differential Pressures

Duragas machines can generate differential pressures up to 4.5 bar (65 psi) in a single stage.

High Inlet Temperature:
+225°C (+437°F) Operating,
+280°C (+536°F) Design.

High Inlet Pressure:
94 barg (1363 psig) Operating,
163 barg (2360 psig) Design,
ASME B16.5 Class 1500 Flanges.

High Differential Pressure:
Single Stage,
4 bar (58.0 psi) Operating Differential.

Low Inlet Temperature:
-100°C (-148°F) Operating,
-170°C (-274°F) Design.

Low Inlet Pressure:
22.6 mbar (17 Torr) absolute.

Multi-stage Compressor Package
We can supply a multi-stage package to generate a high differential pressure, with intercooling to limit the overall temperature rise if required.

Features of the Duragas Series

Rotors and Shafts

Two rotors, mounted on horizontal shafts, will rotate in opposite directions through a pair of timing gears. The profile and finish of the rotors will be such that accurate clearance will be maintained between the two and between rotors and castings. Each rotor is of unit construction with an integrally cast shaft. All rotors are statically then dynamically balanced after final machining.


Each rotor is mounted in a cylindrical roller bearing at the non-drive end to allow for axial expansion of the rotors and a double-row, deep-groove ball bearing at the drive (fixed) end. Blower bearings are of the anti-friction type with adequate axial thrust compression. The bearings are as close as practicable to the impeller to give maximum rigid support and eliminate any tendency to deflection. Bearing life (B10) is rated in excess of 50,000 hours.


A large and wide gas space will be provided in the end covers between the inner/gas seals and the bearing lubrication oil seals. This interspace volume will be provided to guarantee no lubricating oil can migrate into the process gas stream.

Integral Gears

Heavy-duty timing gears have single, helical teeth, precision manufactured so as to maintain the relative position of the rotors and to ensure quiet operation and minimal backlash. The gears are clamped for easy replacement and timing adjustment. For high-speed operation, a forced (pressurised) lubrication system can be provided.

Integral Lube Oil Sump

A splash lubrication system is employed. Oil will be distributed to the gears and bearings while in the sump. The lubrication system will be completely self-contained and normally requires no attention apart from checking the oil level and periodic oil changes.


Casings are provided with flange drilling to suit the application. Full flanges are available if required.

Bare-shaft Blower Assembly

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