FLUSHING
BASKET STRAINERS
are
a type of modified simplex strainer, having the drain port
connected to the bottom of the strainer basket, enabling "flushing"
of retained particles when the drain valve is opened. The
effectiveness of the cleaning is dependent upon the differential
pressure of the system compared to the (presumably)
atmospheric pressure of the drain port. Other factors include
the particle characteristics; if they tend to be hard and
non-deformable, this strainer design provides a low-cost
approach for reducing labor related expenses. Most designs are
modified cast strainers, thus pricing and lead time are low.
BACKWASHING
BASKET STRAINERS
use some of the fluid already
strained to dislodge particulate embedded within the filter element.
This is accomplished by effectively reversing the flow through
the element and out the drain port using an internal nozzle
assembly which slowly rotates within the element.
Approximately 5% of the flow is used for backwashing the filter
element and the duration of the cleaning cycle is typically 3-5
minutes. This style strainer supports flow rates typical of
pipeline sizes from 2" to 48" and due to the backwashing nature,
are mostly used for applications using water.
MECHANICALLY CLEANED STRAINERS
are a design pioneered by Ronningen-Petter (now
owned by Eaton)
are used mostly for non-water fluids or for applications
where it is important to minimize product loss. Very often
these fluids are either viscous or hazardous such as paint, wax,
petroleum products and food/beverage applications. An
internal disc wipes the surface of the element, pushing all of the
retained particles to the purge chamber. When the drain valve
is opened, the system pressure flushes the particles out the drain.
The cleaning cycle is typically <1 second and the volume of
solids/fluid <1 gallon. The internal stroke frequency and the
purging frequency are set with programmable timers.
TUBULAR BACKWASHING FILTER SYSTEMS
are
another design pioneered by
Ronningen-Petter and are used for applications
requiring fine particle retentions (as fine as 100
mesh [150 microns]). Tubular
backwashing filter systems temporarily reverse the flow through the
filter element to backwash and dislodge embedded particulate to a
drain port.
When continuous flow is required, the filter system will consist of
multiple chambers, ensuring that a minimum flow and a constant
discharge pressure is maintained during the cleaning cycle.
MULTIPLEXED SYSTEMS
refer to several automatic
strainers or filters installed on a single pipeline and controlled
by a single control panel in support of high flow rates, large
particles loads and viscous fluid applications. These systems share
a common inlet, outlet and drain manifold.
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