Operation
The Alfa Laval CHNX 418 B31-G is a horizontal de-sludging centrifuge built for the two-phase separation of wastewater, crude oil tank bottoms, municipal sludge-thickening, industrial sludge dewatering, paint sludge handling, and similar applications. It is a specialized variant of the NX 418 decanter centrifuge, engineered for processing sludges containing flammable, explosive, or otherwise hazardous constituents.
The defining feature of the CHNX 418 is its inert gas purge system installed for nitrogen purging of the operating space, including the container vessel and inlet feed pipe housing. This maintains a non-ignitable atmosphere within the bowl cavity, mechanical seal areas, and casing throughout operation.
With a 20 HP motor, the CHNX 418 decanter has a bowl RPM of 4,000 and processes 5-20 m3/hr (22-88 GPM) depending on duty. The unit generates 3,150 G-Force. The machine is built on an Alfa Laval CHNX 418 originally manufactured for ATEX service in classified hazardous locations. Dolphin remanufactures it and verifies the nitrogen purge system function in its Warren, Michigan shop.
Dolphin Centrifuge is the independent specialist in Alfa Laval centrifuges. Apart from Alfa Laval itself, Dolphin is the reliable source for quality Alfa Laval machines: reconditioned Alfa Laval NX, CHNX, and G2 decanters sold and rebuilt in the United States, plus turnkey systems, parts, and service, built on 40+ years of Alfa Laval experience and led by Sanjay Prabhu, M.S.M.E.
Every CHNX 418 Dolphin supplies is a genuine Alfa Laval decanter, stripped, rebuilt to OEM specification, balanced, and run-tested with the nitrogen purge system verified in Dolphin's Warren, Michigan shop. Dolphin is an independent remanufacturer and is not affiliated with Alfa Laval.
CHNX 418 Specifications
| Model Type | Alfa Laval CHNX 418 B31-G Decanter Centrifuge |
| Rated Capacity | 5-20 m3/hr (22-88 GPM) depending on duty |
| Bowl Diameter | 418 mm |
| Bowl Speed | 4,000 RPM |
| G-Force | 3,740 RCF |
| Drive Motor Power | 20 HP |
| Auger Differential Speed | 1 ~ 50 RPM |
| GearBox Ratio | 1 : 159 (2.5 kN-M) |
| AE (Area Equivalent) | 1,565 |
| Conveyor Protection | Carbide Tile or Tungsten Carbide Hard-Surfacing |
| Inert Gas Purging | Gas Nozzle Manifold for Inert Gas blanketing of Vessel and Glands |
| Hazardous-area design | ATEX (original Alfa Laval build) |
Applications
The Alfa Laval CHNX-418 Decanter is used for the following applications.
- Steel Mill Tar Recovery
- Ethanol Extraction Centrifuge
- Waste Oil De-sludging
- Crude Oil Tank Bottom Sludge
- Municipal Wastewater
- Pyrolysis Sludge Separation
- Liquid Humus Fertilizer
- Sludge Thickening & Dewatering
Why Nitrogen Purging?
When a centrifuge processes sludge containing flammable solvents, the high-speed rotating bowl creates centrifugal aerosolization and off-gassing of volatile organic compounds. In standard centrifuges, these vapors can accumulate to ignitable concentrations inside the casing. The CHNX 418 addresses this risk by continuously flowing inert nitrogen gas through the bowl cavity and discharge areas, displacing any oxygen and preventing combustible mixtures from forming.
This approach is recognized by ATEX standards as an effective protective measure for centrifuge applications in Zone 1 and Zone 2 hazardous locations. Contact our engineering team to discuss whether the CHNX 418 or another explosion-proof centrifuge configuration is appropriate for your specific solvents and process conditions. See also our decanter centrifuge overview and decanter centrifuge applications for broader context.
Need the CHNX 418 for a Hazardous Application?
Dolphin Centrifuge supplies remanufactured CHNX 418 decanters, built on Alfa Laval machines originally manufactured for ATEX service, for flammable sludge processing. Contact our engineers to review your application.
Frequently Asked Questions
What does the 'CH' designation mean in CHNX 418?
The 'CH' in CHNX 418 stands for 'Chemical Hazardous'. It identifies the nitrogen-purged variant of the standard NX 418 decanter centrifuge, originally manufactured by Alfa Laval for ATEX service and intended for processing flammable, explosive, or otherwise hazardous sludges and slurries. The continuous inert gas purging system maintains a non-ignitable atmosphere throughout operation.
Why does the CHNX 418 use nitrogen purging instead of explosion-proof motors?
Explosion-proof motors alone do not protect the bowl interior from ignitable vapor concentrations. The CHNX 418 uses continuous nitrogen purging because the high-speed rotating bowl can aerosolize volatile organic compounds and create ignitable mixtures inside the casing. Nitrogen displacement eliminates oxygen from the bowl cavity and discharge areas, preventing combustible mixtures regardless of the electrical rating of the motor.
What industries use the Alfa Laval CHNX 418?
The CHNX 418 is used in solvent recovery and recycling, pharmaceutical manufacturing waste processing, chemical plant sludge with flammable content, petrochemical refinery slurries, paint and coatings waste, ink and resin waste dewatering, and adhesive and polymer slurry separation — any application where the feed contains flammable solvents or vapors requiring ATEX-classified equipment.
How does the CHNX 418 compare to the standard NX 418?
The CHNX 418 retains all the separation performance of the standard NX 418 (418 mm bowl diameter, variable speed drive) while adding continuous nitrogen purging, explosion-proof motors, and sealed casing with inert gas inlet and vent connections. The CHNX was originally manufactured by Alfa Laval for ATEX service. The separation characteristics (G-force, scroll speed differential, pond depth) are unchanged from the base NX 418 decanter.
Does Dolphin Centrifuge supply and service the Alfa Laval CHNX 418?
Yes. Dolphin Centrifuge supplies reconditioned Alfa Laval CHNX 418 decanter centrifuges from our Warren, Michigan facility. Each unit is fully disassembled, inspected, rebuilt to OEM specifications, and tested with the nitrogen purge system function verified before shipment. We also stock replacement parts and offer field service. Contact (248) 522-2573 for availability.