9-15 Chlorination unit descaling. Perform this procedure when an excess of white mineral scale shows on the
chlorination unit cells (anodes), when there is a decrease in flow rate to holding tank as shown on makeup flowmeter
(Figure 9-5), or when there is an absence of solution at top of the cells. When any of these conditions are observed,
excessive scale build-up or low flow is occurring Flush and descale unit. Flushing procedure uses water from seawater
system to flush chlorination unit. Holding tank continues to supply chlorine to product water during descaling and flushing
If EMS alarms are activated during descaling procedure, acknowledge alarms
according to paragraph 9-12, step p.
9-15.1 Initial flushing with seawater
Make sure seawater system is operating and providing seawater to chlorination system through seawater valve
SW47 or SW48.
Turn alarm ON/OFF switch on control cabinet (Figure 9-9) to OFF.
Turn function switch on control cabinet (Figure 9-9) to OFF/RESET.
Position chlorination unit valves as indicated below:
o = open
x = closed
A = position A
B = position B
C = position C
CU VALVE NO
Position valve CU4 halfway between positions A and C to reduce flow through system.
Turn brine pump ON/OFF switch inside control cabinet (Figure 9-10) to OFF.
Turn cooling water flowmeter OFF by dosing valve at bottom of flowmeter (Figure 9-5).
Turn makeup water flowmeter OFF by dosing valve at bottom of flowmeter (Figure 9-5).
Turn function switch on control cabinet (Figure 9-9) to FLUSH.
Allow seawater to flow through chlorination unit for about 5 minutes, then turn function switch on control
cabinet to OFF/RESET.
Open chlorination valve CU9 to allow chlorination unit to drain. If sump appears to be overfilling, partially
close valve CU9 to reduce drain flow to sump.
After chlorination unit has drained, close valves CU8 and CU9 and turn valve CU5 to position C (OFF).
Flush unit with acid according to paragraph 9-15.2
9-15.2 Flushing with acid
9-15.2.1 Acid tank preparation
Wear rubber gloves, safety goggles or faceshield, and chemical dust mask when
working with acid crystals and acid solution.
Remove lid to acid tank and fill with about 25 gallons of drinking water from fill hose attached to bib in void 2 port
above holding tank