Screening panels are carried on a vertical travelling path, between
chains suspended from substantial sprockets on a head shaft. The
chains/screen panels and guides are contained in a carbon steel
or stainless steel screen support structure. A feature of this
type of screen is its high capacity per width ratio and ability
to deal with large variations in water levels and depths.
Dependant upon the size of screen, the frame will be fabricated
from rolled steel sections suitably braced to withstand loads
or from pressed and fabricated plate in stainless steel or carbon
steel. The head section is fabricated to hold the head shaft in
guides and incorporates spray pipes and discharge trough. Covers
are manufactured in stainless steel and have inspection windows
fitted as standard.
The chains are at pitches of 300 or 450mm depending on the size
of the screen. Links are carbon steel plated or stainless steel
and are fitted with moulded nylon rollers sized to suit the screen.
Drive to the head shaft, which is supported in heavy duty roller
bearings, is normally by a shaft mounted gear reducer often with
two speed motor. Motors can be fitted with torque limiting coupling
or preferably current sensing overload in control, to prevent
damage due to obstruction or overload.
The panel frames are of mild steel or stainless steel construction
secured to the chain by stainless steel bolts. The frame carries
plastic perforated panels or stainless steel meshes depending
upon application and can be removed from outside the screen. The
trailing edge of the panel is extended forward to form platforms
for lifting larger debris. Each panel is fitted with UHMW nylon
shaped seal plate. This corresponds with fixed side seals to give
minimum clearance at sealing between clean and unscreened water.
The screens are fitted with spray header pipe (s) each with a
row of jets to wash debris from the panels into the debris trough
incorporated into the head covers. Debris troughs can be fitted
with extra sparge water supply, dependant upon debris loading.