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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 wa-
ter 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 has been left “unpickled” for an extended length of
time and biological growth is present, it is recommended that the system is 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 sys-
tem, remove the prefilters and examine their condition If the housings are full of smelly discol-
ored 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’s discolored and smells bad, perform an SC-2 cleaning with an alternate source of unchlori-
nated 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. One way to do this is to find a camp stove and use a large
stainless steel pot to heat the solution in. 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. Periodi-
cally stop and reheat the solution.
Perform the cleaning procedures while the ship is in acceptable sea water for purging and testing.
• There are two types of cleaners: acid and alkaline. The acid cleaner (SC-3) will remove min-
eral scaling. 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 with both chemicals is recommended. The acid cleaner
should be used first. If the membrane fails to respond to both cleanings, this is an indication
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 feed pressure begins to rise due to fouling or
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 exist-
ing conditions. Other conditions can cause high pressure such as cold feed water or clogged
filters. Low product flow is usually due to low voltage, 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