45
The Membranes
The membranes need to be cleaned only when operating pressures have risen more
than 10% 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
conditions. Cold water can also cause high pressure. If the system pressure is in-
creasing and production is dropping off it is likely the membrane is becoming fouled.
Keeping a log of the basic operating parameters can help show a problem before a
critical shutdown occurs.
There are two types of cleaners: acid and alkaline. The acid cleaner (SC-3) will remove
mineral 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 recommend-
ed. 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 membranes. Contact Spectra
Watermakers before removing a membrane.
If known bio-fouling is present, the SC-2 may be used first. Use warm water if possible,
up to 120° F (45°C) is recommended as it greatly enhances the effectiveness of the
cleaners.
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.
Before running the system, remove the prefilters and examine their condition If the
housings are full of smelly discolored water, the system was not properly stored. Install
clean prefilters.
Next check the membrane. Attach the brine discharge service 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 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.
MAINTENANCE, continued...
Summary of Contents for LB-20000
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