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SOP1 – Ballast Operations
7
second, and lastly the small vent connected to pump seals. Let pressure build to 5-10 psi, then
shut off priming water at the intake port.
Position one operator at an IMAC interface and a second operator at the to-the-sea ‘block’ valve
located just downstream from the #1 (red-upper) pinch-valve. If you haven’t done this yet,
initiate IMAC data logging by starting an ‘event’ on the IMAC home-screen. No data will be
logged until this ‘event-start’ step has been completed.
The VFD for pump-1 (control) is set at moderate flow with rpm control mode at 700 rpm. Upon
hearing ‘START-ONE’ from the blocking valve operator an IMAC operator immediately presses
start and announces “START” to the blocking valve operator. At that point the “blocking valve”
operator smoothly and without delay opens the valve about 4-clicks checking for pump rotation
(visual and/or motor sounds), DP gauge movement, and pinch-valve discharge pressure gauge
movement to show pump is spinning up and pressure/flow are building. Remember to lock the
part-open valve into a notch. Immediately repeat the start-up sequence for pump-2. At 700 rpm
let flow build and stabilize in both pumps. Now adjust pinch-valve for around 50-75 kpa and
tweak block-valve to create discharge pressure on the pump around 10-15 psi.
When flow/pressure are stabilized as above for both pumps then manipulate pump commands
and positioning of pinch and ‘block’ valves to suit flow and pressure goals of the test event. On
final approach to target flow and pressure transition pumps to flow-control, adjust to target flow,
and lastly use valves appropriately to get the rest of the way to target pressure.
Parameters of pressure and flow during operations should rarely exceed 35 psi or 310 m
3
h
-1
.
Pressure is affected during adjustments to flow; however, in flow-control mode pressure
adjustments will not affect flow until pressures over 55-60-psi where pumps will slip, begin to
dead-head, and then shut down. Note that small movement of 8” butterfly ‘block’ valves result in
large pressure variations so use the pinch valves to fine-tune. Thus the procedure for pinch and
‘block’ valve adjustment utilizes the ‘block-valve’ as coarse adjustment and the pinch-valve for
fine-tuning: position an operator at the IMAC screen or at pump-discharge mechanical pressure
gauge to monitor pressure. To reach target pressure dial in about 50-kpa on pinch-valve and very
slowly close ‘block’ valve until 10-15 psi appear on pinch-discharge mechanical gauge or about
20 psi on the pump-discharge IMAC or mechanical gauge. Drop ‘block’ valve in notch. Slowly
close pinch-valve until around 100 kpa appear on differential pressure-gauge, or 30 psi appears
on pump-discharge, whichever comes first. If not yet to 30 psi, slightly increase restriction at
‘block’ valve. At this point, pressure will be extremely responsive to tiny movements of the
‘block’ valve. Be ready to ease if pressure observer sees pressure over target.
The pinch-valve is subject to repetitive and sometimes severe pressure oscillation (panting) if
closed too far. Usually differential pressure exceeds 100 kpa before this occurs. If this condition
occurs, open the pinch-valve until panting stops and begin the adjustment process over again
with a little more emphasis on the block-valve this time.
When desired flow and pressure is established, flow may be transitioned to/from vendor and
from over-board to tanks and sampling can proceed as dictated by the test plan and SOP 4.