Hoffman Flatbed Vacumatic Filters
Hoffman Vacumatic Filters are flatbed vacuum
units. A continuous metal conveyor belt supports the disposable
media, while a heavy-duty Hoffman exhauster creates a vacuum
beneath the media. As liquid increases and, at a preset limit,
a vacuum switch causes the belt (and media) to be indexed. As
media is newly exposed, it can be pre-coated by dirty liquid
prior to entering the vacuum chamber.
The Vacu-Matic relies on the flow of air
to perform three major functions. First, air is used to dry
the cake prior to sludge removal. This minimizes loss of process
liquids and reduces sludge disposal costs. Second, using the
optional air skimmer, air flow is directed by the exhauster
discharge over the liquid pool to skim away floating contaminants.
Third, air passing the filter chamber aerates the cleaned liquid.
This is particularly important in the case of coolants to control
bacterial growth and resulting coolant rancidity.
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Vacu-Matic: Hi-Flo-Matic Operation
The filter feed pump supplies the Vacu-Matic
with process fluid from the dirty tank. This liquid is pumped
to the distributor and evenly apportioned across the filter
bed pool. The bed consists of a flat wire belt supporting the
filter media. A Hoffman exhauster or centrifugal blower produces vacuum in the chamber
beneath the filter bed, drawing the liquid through the media
and the built up deposit of solids (filter cake). When the pressure
drop across the filter cake/media reaches a given limit, an
electrical switch is closed. This indexes the media and, as
a result, discharges spent media and dried filter cake into
the disposal container. At the same time, clean media is drawn
onto the filter bed. Both the vacuum in the chamber and the
liquid level drop due to the inrush of liquid through this fresh
media. This sudden flow builds the filter cake back to a functional
level. The clean liquid passing through the fliter cake and
media drains into the clean liquid compartment of the holding
tank. A "water leg" is maintained in the clean overflow pipe
to sustain a vacuum in the filter. Where excessive floating
solids or tramp oil exist in the incoming liquid, discharge
air from the vacuum producer can operate an optional air skimmer.
This moves floating materials toward the dirty end for removal
as media is indexed. Should the filter bed become flooded due
to mechanical malfunction or unexpected impurities in the process,
the liquid level is reduced via the overflow slot connected
to the side gutter. This is connected to an overflow drain pipe
dumping into the dirty compartment of the holding tank.
to view Vacu-matic Filter Sizing specifications