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SOP1 – Ballast Operations
9
necessary. Upper hatches may be open for observation and insertion of a sonde but will be
closed while water is held after filling.
Scant head-space remains once tank-level-indicators (TLI) read 300 m
3
. Therefore, plan shut
down procedure in advance. If tank-1 is ahead, synchronize by slowing pump-1 pump down.
This should only affect the control tank (tank-1 aft) since this tank was transitioned to uptake
first, and it’s pump may thus be slowed without impacting flow to the treated (#2 forward) tank.
To stop filling tanks pumps are either stopped or system is set back to sea-to-sea mode. Before
doing either sampling is halted and any challenge-condition enhancement injection has been
deactivated. Shutdown sequence for treatments that cannot be run in sea-to-sea mode due to
toxicity will be specified in the test-plan but probably will involve pump shut-down and tank
isolation valve closure while still valves are in uptake mode. For systems that do not create
toxicity the pumps and pipes assembly will be put back on sea-to-sea and sampling will cease
immediately. Then injection will cease, the vendor bypass will be opened and the vendor can be
shut down. Once this has occurred and the vendor no longer needs flow, pumps may be stopped.
A ‘soft’ ramp-down in pump-speed is not required. The pumps are not positive displacement so
water in motion will coast gently to a halt. Check-valves then function to prevent back-flow
while operator closes primary and secondary tank isolation valves. Check both lower tank
hatches and secure tighter if weeping/dripping. Deploy into each tank a calibrated and logging
multi-parameter instruments through upper tank hatches (SOP 5) before closing the hatch and
excluding light. Now clean and reconfigure the pump-pipes-assembly per the below.
2.5. Cleaning and Preparing the Pipes and Pumps to Rest between Uptake and
Discharge Operations
Using municipal potable water, raise intake hose to storage position with foot-valve completely
above water. Open all bottom drain and air-vents. Position butterfly valves half-open except
overboard discharge valve (closed) and if tanks contain water the primary and secondary tank
isolation valves (closed) as well as drains on 8” under-tank trunks (closed). Wait 10-minutes for
pipes to drain out. Close sea-strainer primary valve and flush pipes with potable water via intake
port near sea-chest. Sequentially shut bottom-drains and air-vents as water begins to flow from
each. Turn off potable water when solid water comes out of upper air-vents. Open bottom drains
except for under-tank trunks. Partly open main overboard discharge valve. Turn off power to
VFD’s and also enhancement injectors after the mixing tanks and hoses are cleaned as per SOP
3.
2.6. Discharge operations (DC), emptying tanks in series
Tanks are discharged in series, with the treated (#2 forward) tank discharged first lowering
potential for interaction between treated and control water and associated risk of sample
contamination. Close bottom drains and set valve line-up for recirculation tank-2. Open bottom
drain on section of ballast pipe isolating sea-suction from tank-suction (double-block) to avoid
contamination. Recirculation mode fills pump, pipes, and primes sampling system without
actually discharging. Tank head will prime the system. Open primary and secondary tank
isolation valves and close air vents once solid water emerges from them. Before pump-start,
twice confirm valve line-up is correct and note tank pressure-head appearing as 5 or 6 psi within
the pump and pipes assembly. If this pressure is not present, then valve line-up is not correct.