Cooling
water systems are
protected from corrosion
by normal chemical
treatment programs when
operating. When cooling
systems are out of
operation all protection
is lost. It is important
to protect these systems
during winter lay-up and
storage.
Why
lay-up the cooling
system?
Most
piping and equipment
will remain damp through
moisture condensation or
inadequate draining and
drying. Upon start-up,
the corrosion particles
can cause strainers and
small lines or ports to
become plugged up. In
addition to the natural
corrosive effect of the
water, bacterial growth
can accelerate the
corrosion rate, and also
produce disease causing
organisms. Therefore, it
is very important that
proper treatment
precautions are used
whenever a water system
is idle for any period
of time.
There
are three common types
of tower lay-up
procedures:
Wet
Lay-up
"Wet
lay-up is generally
accomplished by shutting
the system off. In most
instances, the water is
self-draining into a
sump and the tower basin
and return piping are
dry. In this instance,
some of the piping is
exposed to moisture and
some of the piping and
equipment is exposed to
stagnant water during
the off-season.
Dry
Lay-up
Dry
lay-up is just what it
means, draining the
system from all areas.
This procedure exposes
equipment and piping to
moisture all during the
off-season. If possible,
open the equipment and
piping immediately for
inspection and allow to
air dry.
Wet/dry
Lay-up
This
type of lay-up generally
is used in comfort
systems by draining the
system to just below the
roofline to prevent
freezing. The tower and
some of the piping are
exposed to moisture and
the remainder of the
piping is exposed to
stagnant water during
the off-season.
Corrosion
protection can be
achieved in all three
instances by following
this procedure.
One
week prior to shutting
down the system,
maintain the
inhibitor/dispersant at
twice the normal
operating levels, and
set the tower bleed rate
at double the normal,
i.e., keep the TDS at
1/2 normal operating
range. This procedure
will help to disperse
any inorganic fouling.
A
non-oxidizing biocide
should be added 24 hours
before shutdown to
reduce bacterial growth
during the idle period.
We recommend using the
maximum normal dosage of
any microbiocide
currently in use
The
system can now be shut
down as you wish: Dry,
"Wet or Wet/Dry. To
observe the level of
corrosion protection, a
corrosion coupon can be
inserted in the coupon
rack, to stimulate the
general system prior to
initiating the shutdown
procedure.
If
a wet system is to be idle
for long periods, we
recommend adding biocide
three months and
recirculating throughout
the system for 12 hours.
"Water
systems or equipment that
are drained should be
rinsed. However, mud or
debris in the bottom of
sumps or tower basins
should be cleaned out
immediately following
shutdown.
It
is important to make sure
the proper personal
protective respiratory
device is used before
working directly in the
mist of a cooling tower or
other aerosol-producing
device. Legionella
bacteria are likely found
in systems where particles
are airborne. |
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