Chemical Engineering June 2022 - 23

Facts At Your Fingertips
Clean-in-Place (CIP) Systems
Department Editor: Scott Jenkins
C
leaning equipment surfaces is
critical for processes involving
biological materials to prevent
microbial contamination. Clean-inplace
(CIP) systems play a key role.
In addition to preventing contamination,
CIP systems also remove grit,
scale and organic matter, which may
affect
process
performance.
This
one-page reference provides information
on CIP system equipment
and operating considerations for
bioprocessing facilities.
CIP equipment
CIP systems supply fluid to a spray
device inside the vessel, which sprays
the solution onto the vessel walls. A
variety of spray devices are available,
including static sprayballs and fluiddriven
orbital cleaners. Sprayballs are
high-flow, low-pressure devices often
used to clean tanks smaller than 15-ft
dia., while fluid-driven orbital cleaners
are low-flow, high-pressure devices
used for tanks greater than 15-ft dia.
Tanks. Tanks are typically constructed
from 304L or 316L stainless steel.
Internal welds should be ground
smooth and dead spots should be
minimized. Internal polishing of CIP
vessels is usually not required. Detergent
tanks should be equipped with
agitators to ease the preparation of
detergent solutions.
Pumps. There will likely be multiple
unit operations and tanks using the
same CIP solutions, but with different
flow and pressure requirements. To
address this situation, variable-speed
drives (VSDs) or parallel pumps (systems
with different flows and heads)
may be used to meet the range of requirements.
Pumps are normally centrifugal,
often with VSDs. Net positive
suction head (NPSH) requirements
are an important consideration, due
to the elevated temperatures required
for some CIP fluids. Hydraulic losses
for spray nozzles and equipment
(heat exchangers, sterilizers and
more) need to be calculated based
on vendor information.
Piping. Key considerations of piping
design for CIP systems include the
proper design of CIP circuits, the ability
to drain CIP lines,
and the appropriate
segregation of the
CIP system from
the process being
cleaned. Ideally,
dead legs should be
no longer than two
pipe diameters, and
the overall system
should be designed
to drain completely.
Lines should be
sized for fully turbulent
flow. The
CIP supply
FIGURE 1. In this typical
CIP system, CIP solution
is sprayed into the tank
to clean internal surfaces,
and is drained or pumped
through a separate CIPreturn
line
Process
vessel
Process
CIP return
CIP return pump
general practice is to have a velocity
range of 5 to 7 ft/s. All horizontal lines
should be sloped to a drain point,
and low points must be equipped
with drains. The minimum slope of
the pipe should be at least 1/16 in.
per ft. Valve selection should avoid
non-drainable conditions or crevices
that will not be cleaned. So-called
" clean " ball valve designs are available
for sizes 6 in. and less. For larger
sizes, hygienic butterfly-valve designs
should be considered. The tie-in point
between the CIP system and the process
should be either a block-andbleed
connection, or a line break.
Instrumentation. Generally recommended
instrumentation for CIP processes
includes the following:
* Visual sightglasses for CIP supply
and return lines
* Temperature indicators on the caustic,
acid and rinse-water tanks
* Conductivity transmitters in the CIP
supply and return lines
* Temperature indication and control
on the cleaning solution heater
* Temperature indication in the CIP
return line
* Level indicators on all tanks
* Differential pressure indicators
across filters and heat exchangers
* Limit switches confirming position
of crucial valves
CIP operation
A typical CIP sequence includes the
following elements:
Process heel drain. A complete
drain of the heel is needed to minimize
waste and avoid contamination
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JUNE 2022
of the cleaning fluid.
Pre-rinse. The primary objective of
the initial rinse is the mechanical removal
of dirt. Water recovered from a
later step in the CIP sequence is used
for the pre-rinse step. The pre-rinse
effluent stream may need to undergo
a bio-deactivation process before being
sent for further waste treatment.
Detergent wash. This step involves
chemical cleaning to remove remaining
dirt. The detergent solution is circulated
through the system. The solution
type and concentration should
be determined by plant experience.
While a 2-4 wt.% caustic solution is
commonly used in this step, an acidbased
detergent (or both) can also be
used, depending on the type of dirt or
other contaminants present.
Water rinse. A once-through rinse of
clean water is typically used, with no circulation.
This substantially reduces the
amount of residual materials from the
detergent wash step. If no acid wash
is used, this water rinse step becomes
the final rinse prior to either sanitization
or sterilization. The rinse water should
be collected for reuse as the pre-rinse
fluid used in the next CIP cycle.
Acid wash. The solution used in
this step may be circulated in a loop
(similar to the detergent wash). This
step serves two functions: to neutralize
and remove any remaining
caustic from the detergent wash
step; and to remove any hard-waterscale
deposits that may occur within
the process equipment.
n
Editor's note: The content for this column was adapted from Miley,
B., Riley, J. and Zelmanovich, Y. Large-Scale Fermentation Systems:
Hygienic Design Principles, Chem. Eng., Nov. 2015. pp. 59-65.
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