OM-NI 2/20
19
Condenser Coil & Raw Water System Cleaning
(continued)
There are two methods used for cleaning a system. The
"Immersion Method" and the "Open Loop Recirculation
Method". Immersion cleaning requires the system to be
filled with the water/chemical mix and left to dissolve
the internal growth/contamination for an extended period
of time. It is the least effective of the two methods and
should be considered only if there is a blockage in the
system that stops the flow of liquid. Open loop recircula
-
tion method pumps the mix through the system. It is cap-
tured back into the container where the mix is drawn from
by the recirculation pump. This continuous flow through
the system is the most effective method of cleaning.
When the system is chemically cleaned a forward-flush
and back-flush procedure should be performed. To
forward-flush the water/chemical mix is pumped into the
bottom connection and discharges from the top connec-
tion back into the container. This will be the same flow
direction as the normal raw water flow. It will fill the
coil/manifold/piping with the mix so that all surfaces
are wetted. After the cleaning procedure is done the flow
should be reversed and the system back-flushed with the
mix. Pump pressure in addition to gravity will remove any
larger debris that may be left in the system back into the
container.
It is very important that whenever a system is chemically
cleaned that it must be flushed with fresh water for a mini
-
mum of 10 minutes to remove residual chemical.
Every chemical manufacturer provides dilution ratios and
gallons of chemical required for the size system that you
have. They also have recommended cleaning times for
average or heavy fouling of the system. Some chemicals
have color indication or test strips to monitor strength
of the solution so that you know when to add more or
replace as needed. A visual inspection inside the chemi-
cal container will also give and indication if the system is
clean. If no more debris is seen entering the container then
it is probably clean.
Upon completion of the cleaning routine and flushing
with fresh water the system should be put back online.
The pressures, amperages and temperatures should be
taken again. If they are still operating high then additional
cleaning may be needed.
It should be noted that on smaller systems the raw water
pumps may have a magnetic drive impeller. This station-
ary impeller may be restrictive to the flow of the solution
during cleaning and it is recommended that it be removed
until the cleaning process is complete. Don't forget to
re-install it prior to doing the post-cleaning system check.
Make sure there is no debris inside the impeller housing
prior to installing the impeller.
When you have a situation where the condenser coil
needs cleaning, do not assume that it is the only part of
the system that is fouled up. Even if the raw water strainer
looks clean the piping and manifold can also be dirty. A
visual inspection of the inside of the piping and manifold
should be done at the time of the cleaning or fresh water
back-flushing.
Maintenance
