Shaking

Shaking can be done manually but is usually performed mechanically in industrial-scale
baghouses. Small baghouses handling exhaust streams less than 500 cfm (14.2 m3/min)
are frequently cleaned by hand levers. However, thorough cleaning is rarely achieved
since a great amount of effort must be used for several minutes to remove dust cakes from
the bags. In addition, these small units do not usually have a manometer installed on them
to give pressure drop readings across the baghouse. These readings are used to determine
when bag cleaning is necessary. Therefore, manual shaker baghouses are not recommended
for use in controlling particulate emissions from industrial sources.
Mechanical shaking is accomplished by using a motor that drives a shaft to move a rod
connected to the bags. It is a low energy process that gently shakes the bags to remove
deposited particles. The shaking motion and speed depends on the vendor’s design and the
composition of dust deposited on the bag (see Figure 1). The shaking motion is generally
in the horizontal direction.

Fig.1. shaking

The tops of the bags in shaker baghouses are sealed or closed and supported by a hook or
clasp (see Figure 2). Bags are open at the bottom and attached to a cell plate. The bags
are shaken at the top by moving the frame where the bags are attached. This causes the
bags to ripple and release the dust. The flow of dirty gas is stopped during the cleaning
process. Therefore the baghouse must be compartmentalized to be usable on a continuous
basis. Shaker baghouses always use interior filtration (dust collected on the inside of the
bags).

Fig.2 Bag attachment for shaker cleaning baghouses

Fig 3. Typical shaker baghouse

In a typical shaker baghouse, bags are attached to a shaft that is driven by an externally
mounted motor (Figure 3). The bags are shaken, and the dust falls into a hopper located
below the bags. The duration of the cleaning cycle can last from 30 seconds to as long as a
few minutes, but generally lasts around 30 seconds.
Frequency of bag cleaning depends on the type of dust, the concentration, and the pressure
drop across the baghouse. The baghouse usually has two or more compartments to allow
one compartment to be shut down for cleaning.
Figure 4 shows a typical shaking mechanism of a shaker baghouse. The bags are
attached in sets of two rows to mounting frames across the width of the baghouse. A motor
drives the shaking lever, which in turn causes the frame to move and the bags to shake.

Fig. 4 Detail of a shaking lever system

Shaking should not be used when collecting sticky dusts. The force needed to remove
sticky dust can tear or rip the bag.
Bag wear can occur at the top of the bag where the support loop attaches; it can also be a
problem at the bottom of the bag where it is attached to the cell plate. Proper frequency of
bag cleaning is therefore important to prevent premature bag failure.
Typical design parameters for shaking cleaning are given in Table . Occasionally shaking
cleaning is used along with reverse-air cleaning to promote thorough bag cleaning for
applications such as coal-fired utility boilers.

                                                          Shaker cleaning parameters