Three-Screw

Three-Screw

How they convey fluids:

The ALLWEILER® and IMO® three-screw pumps are rotary‚ self-priming positive displacement pumps. The pumping elements consist of three moving parts: the power rotor (main screw) and two symmetrically opposed idler rotors‚ all operating within close fitting housing bores. The incoming process fluid is conveyed by the rotating power rotor by means of the cavity formed with the intermeshing idler rotors. These two hydraulically driven shafts‚ which only make rolling contact with the power rotor‚ regulate the amount of internal slip. From suction to discharge the fluid is transferred by means of a series of constantly forming and re-forming chambers until it reaches the casing outlet. Symmetrical pressure loading on the power rotor eliminates the need for radial bearings to absorb radial forces. The idler rotors generate a hydrodynamic film which provides radial support similar to journal bearings. Axial loads on the power rotor and idler rotors‚ created by differential pressure‚ are hydrostatically balanced. By this design arrangement high differential pressures can be managed. To achieve higher flow rates‚ double ended or double suction three-screw pumps can be applied‚ with the flow pattern being the same as a two-screw pump.

Strengths of the technology:

  • High pressure boost capabilities even when handling low viscosity fluids
  • Pump with one of the highest overall efficiencies when handling heavy crude
  • Simple pump design with only three rotating parts and one shaft seal
  • Pulse-free flow with extremely low vibration and noise levels
  • Designs available to the latest edition of API 676
Maximum Flow Rate Differential Pressure Viscosity Range Min to Max Max Fluid Temperature Max Solids Content Max Free Water Content Max Gas Content Colfax Brand & Series
54 m3/h
240 usgpm
100 bar
1450 psi
1 to 2000 cSt 80°C
175°F
0.5% 90% 5% Allweiler EMTEC series
90 m3/h
400 usgpm
103 bar
1500 psi
4 to 5400 cSt 107°C
225°F
0.5% 10% 5% Imo 6D series
90 m3/h
400 usgpm
138 bar
2000 psi
4 to 5400 cSt 107°C
225°F
0.5% 10% 5% Imo 12D series
660 m3/h
2900 usgpm
138 bar
2000 psi
10 to 5400 cSt 107°C
225°F
0.5% 10% 5% Imo 8L series
318 m3/h
1400 usgpm
100 bar
1450 psi
4 to 5000 cSt 250°C
480°F
0.5% 10% 5% Allweiler SN series
130 m3/h
570 usgpm
120 bar
1740 psi
4 to 5000 cSt 250°C
480°F
0.5% 10% 5% Allweiler SM series
750 m3/h
3300 usgpm
21 bar
300 psi
10 to 5400 cSt 260°C
500°F
0.5% 10% 5% Imo 323F series
204 m3/h
900 usgpm
34 bar
500 psi
10 to 5400 cSt 260°C
500°F
0.5% 10% 5% Imo 324A series
182 m3/h
800 usgpm
48 bar
700 psi
10 to 5400 cSt 107°C
225°F
0.5% 10% 5% Imo T324N series

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