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GDX™ Gravity Decker

The GDX™ gravity decker is mainly used for dewatering paper machine broke and for pre-thickening reject pulp. It is available in 2.5 and 3.4 meter diameters.

Design Features of the GDX Gravity Decker

Drum – perforated plates mounted on a drum support assembly.

Vat Seals –  stainless steel wire cables with a thick plastic coating that fit in V-shaped profiles between the drum and the vat at each end. The simple design needs little maintenance and minimizes power consumption.

Drive – a shaft-mounted gear box supplied with guards, belts and sheaves. 

Fabric Cleaning – the cleaning shower header has an internal brush and strainers at each nozzle that allows plugged showers to be cleared from the outside of the GDX by rotating the brush and simultaneously opening a flush valve to purge contaminants from the header.

Hood – manufactured from stainless steel, with fiberglass covers for inspection ports. 

Filter Cloth – a synthetic fabric is shrunk onto the drum.

Wetted Parts – all wetted parts are made of stainless or acid proof steel. 

Operating Principle

The drum is installed eccentric to the vat radius, with more clearance on the feed side than on the discharge side. The feed suspension enters the vat through a full length feed box. The drum rotates in the direction of the incoming feed, carrying the pulp underneath the drum to a compaction zone on the other side where dewatering occurs. Filtrate passes through the perforated deck and is discharged through the open end of the drum and an outlet connection on the vat head. The liquid level inside the drum is lower than the level in the vat outside the drum, creating a static pressure differential that drives filtration.  Pulp discharge consistency can be regulated by removing or adding stainless steel weirs to the overflow wall between the filter vat and the pulp discharge box.

Dimensions (mm)

Filter Model Filter Area (m2) A B C
2545 35.3 5914 3950 3076
2550 39.3 6414 3950 3076
2555 43.2 6414 3950 3076
2560 47.1 7414 3950 3076
2565 51.0 7914 3950 3076
2570 55.0 8414 3950 3076
2575 58.9 8914 3950 3076
3460 64.1 7550 5176 4040
3465 69.4 8050 5176 4040
3470 74.8 8550 5176 4040
3475 80/1 9050 5176 4040

Reliable Operation
The GDX™ gravity drum decker is insensitive to variations in feed flow or feed consistency, and works at a constant speed without instrumentation or regular operator attention. Pulp discharge consistency is normally in the range of 4 to 5% solids, depending on the pulp freeness and feed consistency.

No Droplegs
The GDX needs no dropleg or other vacuum source. The driving force for dewatering is the static pressure difference between the liquid level in the vat and the liquid level in the drum.

Low Maintenance Requirements
The GDX gravity drum has very few wear parts. Because there is no contact with other surfaces (no couch roll), the filter media has a long service life. The drum seal is easily replaced when worn.


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