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DRUM SCREENS
WATER FLOWS FROM OUTSIDE TO INSIDE

Out-in DS
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PURPOSE AND APPLICATION

Drum screens are used to arrest the small debris contained in a large flow of water so that the downstream users remain unobstructed and clean (condensers, exchangers, spray nozzles, membranes, etc.). The debris can be of all types including fish, shrimps, jellyfish, leaves, grass, man-made refuse, plastics, seaweed, etc.

 

Drum screens are used in thermal and nuclear power plants, LNG terminals, desalination and fertilizer plants, drinking water and irrigation plants. They are especially recommended for very large flow rates.

DESCRIPTION

The drum screen is installed in a concrete chamber between two parallel side walls with large apertures. The drum consists of a cylindrical rotor with a cylindrical surface made of side-by-side rectangular mesh panels. The rotor has two bearings and a drive at deck level. The panels travel down into the water. The water flows through the mesh panels into the drum chamber via the upstream inlet, around the outside of the drum and flows out after passing through the mesh via the two side-wall outlets.

 

The debris-laden panels travel up above deck level around the top and down again. One or two spray pipes with fantail jet nozzles located inside the drum screen at deck level, back-wash the panels and remove the debris which are projected into an external collection trough. The debris travel in a deck flume to the debris disposal system (basket, separator, etc.).

 

The screens are normally stopped and are washed periodically when obstructed by the debris. Permanent rotation can be provided.

Drum screen - Outside-to-inside

ADVANTAGES

  • 90 years’ experience

  • Permanently resists high levels of head-loss

  • Large debris-handling capacity

  • Well-suited for permanent rotation

  • Compact civil structure

  • Fully-automatic

  • Fish-friendly option

  • Next to no maintenance required.

  • Cost effective

  • Easy access to the external debris trough

  • No internal debris interference

NECESSARY ANCILLARIES

  • Spray-water supply circuit

  • Head-loss monitoring system

  • Electrical control cabinet

  • Upstream bar rack (25 to 75 mm spacing (1 to 3”))

  • Pit dewatering stoplogs

  • Trash collection system (basket, etc.)

SIZES AND DATA

  • Mesh aperture from 1x1 to 10x10 mm (0.04 to 3/8”) or less upon special request

  • Flow rate up to 170000 m3/h (500000 gpm)

  • Tidal variation: no practical limit

  • Panel frame useful width: 1.3 to 6 m (2 to 13 ft)

  • Wider machines on special request (two-wheel layout)

OPTIONAL FEATURES

  • Two or three-speed operation

  • Seismic qualification

  • Special high travel speed design for handling very heavy debris loads

  • Jellyfish lifting trays

  • Screening medium resistant to fiber build-up

  • Screening medium preventing jellyfish adherence

  • Low pressure water-life protection system

  • “Scoop-a-fishTM” total fish survival system

  • Atex compliance

  • By-pass valves

MATERIALS

  • Drum rotor, mesh carrying structure, hub and shaft, bearing blocks:   
    For fresh-water applications: painted carbon steel or AISI 304L stainless steel     
    For seawater applications: AISI 316L stainless steel with anodes, duplex or super-duplex stainless steel
         

  • Transmission shaft and bearings:         
    For fresh-water applications: carbon steel or AISI 304L stainless steel 
    For seawater applications: AISI 316L stainless steel, duplex or super-duplex stainless steel      
     

  • Bolts, nuts, washers:       
    For fresh-water applications: A2 or A4 stainless steel  
    For seawater applications: A4, duplex or super-duplex stainless steel      
     

  • Small fittings, spray-water pipes:
    For fresh-water applications: AISI 304L stainless steel
    For seawater applications: AISI 316L, duplex or super-duplex stainless steel                 
     

  • Screening mesh frames: 
    For fresh-water applications: AISI 304L stainless steel or composite  
    For seawater applications: AISI 316L, duplex or super-duplex stainless steel or composite  
         

  • Spur gear and pinion:
    Composite materials, carbon steel or cast iron (stainless steel in special cases) 
        

  • Seals:
    Composite materials or rubber   
     

  • Debris-collection trough: 
    GRP, AISI 316L, duplex or super-duplex stainless steel             
     

  • Anodes:   
    None required for fresh-water applications        
    For seawater applications: anodes are required for use with AISI 316L stainless steel and sometimes for duplex stainless steel

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