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Types of Basket Strainers
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Duplex Basket Strainers
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A duplex basket strainer can operate continuously and never has to be
shut down for cleaning. The most popular and convenient type is, in
reality, a specialized plug valve. A diverter plug is carefully fitted
to the strainer body. It permits flow to pass either left or right.
When one basket becomes full, the flow is shifted to the other one.
The dirty basket is then removed, cleaned and replaced, ready for use
again. Another, newer, type of duplex strainer utilizes a diverter
cartridge in place of the diverter plug. This diverter cartridge
diverts the flow through the strainer using balls and operates like a
ball valve. This design’s main advantage is that their is no leakage
from one strainer basket chamber to the other.
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Large Size Duplex Strainers
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A get larger, however, these types of duplex strainer design become
unwieldy and impractical. In these cases a sliding gate valve
arrangement is used to transfer the flow. The valve discs are actuated
by a set of hand wheels. They are synchronized so when one basket
chamber is being opened to receive the flow, the other basket chamber
I being sealed off.
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Applications
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Obviously, duplex basket strainers are valuable in locations where
it is impossible to shut off flow or stop the operation. Examples are
cleaning fuel oil in large industrial oil burners, for all types of
marine applications, straining water in cooling towers, and straining
fluids in continuously running chemical operations.
Most people do not realize that a duplex strainer is useful in
applications other than ones which must run continually. Often it is
desirable to keep something going for a few hours only, but during
this short time the line must not shut down. In filling paint
cans, for instance, there may be considerable variations from batch to
batch. One lot might have an unusually large amount of material to be
strained and the filling line would have to be stopped several times
if a simplex basket strainer were used. A duplex unit avoids this.
Flow can be switched from one basket to the other, as can fill, and
the line can keep running.
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Simplex Basket Strainers
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There are two kinds of basket strainers, simplex and duplex. A simplex
basket strainer is used where the line can be shut down for short
periods to clean or change baskets. It becomes an integral part of the
pipeline and all flow passes through it.
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An Important Consideration
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An important feature of a well designed duplex basket strainer is that
it must never allow the flow to stop. If this is possible, a careless
workman can inadvertently do great damage. For instance, the flow of
lubricating oil to a compressor could be shut off while switching from
one basket to the other. With a properly made duplex strainer it
should be impossible to stop the system. If this is required, a
separate valve can be used.
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