Table 1. Major Functional Components of the ROWPU System (Refer to Figure 3) (continued)
The solenoid operated 3-way diverter valves are
controlled by the system controllers (figure 3, item 14).
The controllers sense the salinity of the product water
output by the membranes. If the product water salinity
is within tolerances, the product water is sent to the
brominator and on to the potable water tanks. If product
water salinity is too high, the product water is diverted
and sent overboard as ROWPU system product brine.
ROWPU System Product
Brine is the by-product of reverse osmosis. The brine
is pumped overboard via the general service system
overboard discharge. The ROWPU system is protected
from the general service system by means of a check
valve that acts as a backflow preventor.
Fresh Water Flush Pump
The fresh water flush pump is a low pressure pump that
is used to clean and to prepare the ROWPU system for
use. It is a 24 Vdc pump controlled by the system
controller. The fresh water pump uses filtered potable
water to purge raw water from the filtration system and
from the raw water side of the reverse osmosis
membranes. When the ROWPU is not in use, the
system controllers automatically perform a fresh water
flush once a week. The fresh water flush serves to
prolong the life of the membranes, and it eliminates
the need to `pickle' the membranes for layup.
The charcoal filters remove sediment and foul odors
from the potable water used during flushing cycles. The
charcoal filters also block bromine and chlorine from
passing into the reverse osmosis membranes. The
charcoal filters are secured when the ROWPU is making
product water, and are protected by cutoff valves and a
water purification monitors and controllers. They control
power to the pumps, monitor the quality of the output
potable water, and monitor system operating pressures.
The system controller turns the high pressure and fresh
water flush pumps ON and OFF as required by system
demands and operating conditions. The system
controller also measures the salinity of the product
water and controls the position of the solenoid operated
3-way diverter valve accordingly. Finally, the system
controllers monitor system operating pressures. Any
system pressure out of tolerance will cause the
controller to stop the process and indicate an alarm.
Power input to the system controllers is 450 Vac
and 24 Vdc.