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Membrane Cleaning
For normal cleaning, the SC-3 Acid Cleaning Compound is used first, then the SC-2 Alkaline Cleaning
Compound. If known bio-fouling is present, the SC-2 may be used first. Using hot water if possible, up
to 120° (45C) is recommended as it greatly enhances the ability of the cleaners to do their jobs.
If the history of the system is unknown or it has been left “unpickled” for an extended length of time
and biological growth is present, it is recommended that the system be cleaned with SC-2, using an
alternate source of unchlorinated fresh water before the system is run under pressure. A simple test can
be performed to see if biological growth has occurred. Before running the system, remove the prefil-
ters and examine their condition. If the housings are full of smelly discolored water, the system was
not properly stored. Install clean prefilters if they were bad. Next, check the membrane. Detach the
brine discharge hose and lead to a bucket. Open the pressure relief valve one turn, and manually run
the system for 30 seconds. Examine the brine water. If it is discolored and smells bad, perform an SC-2
cleaning with an alternate source of unchlorinated water before running the system pressurized. If the
brine is fairly clean, the system can be purged, run normally, and checked for performance. Clean the
membranes only if performance is reduced.
Heating the water is preferable. The cleaning solution throughout the system will heat as it circulates in
and out of the pot. An alternative is to heat the one or two gallons of initial water to 120° on the main
stove before mixing in the cleaner and circulating it into the system. Periodically stop and reheat the
solution.
Perform the cleaning procedures while the ship is in acceptable sea water for purging and test-
ing
, or follow the flushing, purging, and testing procedure given in the “Dry Testing with Artificial
Ocean” instructions.
There are two types of cleaners: acid and alkaline. The acid cleaner (SC-3) will remove mineral scal-
ing. The alkaline cleaner (SC-2) is used to remove biological by-products, oil, and dirt particles that
get past the prefilters. If membrane performance is reduced and they have not been “pickled” recently,
cleaning is recommended. The acid cleaner should be used first. If the problem persists after the acid
cleaning, do the alkaline cleaning. If the membrane fails to respond to both cleanings, this is an indica-
tion of another problem with the system, or that it is time to replace the membrane. Contact Spectra
Watermakers before removing a membrane.
The membranes need to be cleaned only when operating pressures have risen 10% due to fouling, or
when the product quality degrades. The leading cause of fouling is from biological growth that occurs
when the system is left unused without flushing or pickling. Fouling from mineral scaling can happen
during operation under certain sea water conditions, and from rust. Monitor the product salinity and
feed pressure for higher than normal readings for the existing conditions. Other conditions can cause
high pressure such as cold feed water or clogged filters. Low product flow is usually due to low volt-
age, damaged feed pump or Clark Pump. Look for all other causes before cleaning the membrane.
Membrane life can be shortened by excessive cleaning.
The Membranes
