Yearbook 2013/2014 - ehedg

78 Effective tank and vessel cleaning: How different systems can help meet today’s demands
Rotating cleaners
Rotating cleaners rotate around an axis, and they can be
found as fast or slowly rotating types (Figures 3 and 4).
Slowly rotating cleaners use flat or round jet nozzles to spray
the cleaning solution on the tank wall. Unlike spray balls,
the cleaner does not wet all inner tank surfaces at the same
time, but rather, applies a concentrated liquid jet to one
segment of the tank wall at a time. This means that the full
impact energy of the jet can act on this particular segment
and that a thicker liquid film forms on the tank wall, which,
due to its higher energy, achieves better cleaning results as
it runs down to the tank outlet. Without switching the supply
pump on/off, this produces a pulse/pause type of operation
for each segment of the tank that allows the product residues
to be softened and rinsed off. This effect cannot be achieved
by a spray ball.
As a result, the mechanical cleaning effect of the slowly
rotating cleaner is much greater than that of a spray ball.
This even applies if the cleaning solution flow rate is relatively
low. Under normal operating conditions the cleaning medium
consumption is about 30-50% less compared to a spray
ball.
Figure 4. Rotating cleaner in the head of a mixing tank.
Figure 3. Various types of rotating cleaners.
Orbital cleaners
The special characterristics of this type of cleaner are the
round-jet nozzles that rotate in two planes and produce
highly focused high impact jets for intensive cleaning of the
inside surfaces of tanks or vessels (Figure 5). Depending on
the type, the cleaners have two or four nozzles. The nozzles
have an inside diameter of up to 12 mm in accordance with
application requirements. The horizontal and vertical rotary
movement is produced by a turbine gear unit, driven by the
cleaning medium, or by a separate drive such as an electric
or pneumatic motor. The continuous rotation in two planes
produces a finely meshed, net-like pattern of cleaning jets
on the inside wall of the tank. At the end of a full cycle, each
and every point of the tank has been directly subjected
to mechanical impact from a strong jet. A complete cycle
typically takes between 3 and 9 minutes. In practice, orbital
cleaners generally operate at pressures of 4 to 8 bar and
can easily cover an effective horizontal cleaning diameter