Spectra Watermakers LB-1800C, Installation And Operating Manual

Page: 31 / 53

31
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 biologi-
cal growth that occurs when the system is left unused without flushing or pickling. Foul-
ing from mineral scaling can happen during operation under certain sea water condi-
tions, and from rust. Monitor the product salinity and feed pressure bar graphs for high-
er than normal readings for the conditions. Cold water can also cause high pressure.
Low product flow is usually due to fouled membranes which is why we recommend that
you keep a log of the basic operation parameters. If the system pressure is increasing
and production is dropping off it is likely the membrane is becoming fouled.
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 membrane. Contact Spectra Watermakers before removing a membrane.
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. Use hot water if possible, up to 120° F (45C) is recommended as it greatly en-
hances 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 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 if they were bad. Next check the membrane. At-
tach 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 ….