Alfa Laval PureBallast 135 Compact USCG, System Manual

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3.4.22.2 External feed
The external feed is used to fine tune the control of the flow that comes to
PureBallast. It works as an addition to the flow controlled by the control valve
(V201-8).
3.4.22.2.1 Fine tune external feed control (optional)
External feed control allows PureBallast to control the flow delivered from the
vessel’s ballast water system by regulating either the ballast water pump via a
variable frequency driver (VFD) or a valve installed before PureBallast.
If this optional signal is used to control flow to PureBallast, the regulation can
be finetuned to function as smooth as possible.
When the flow in the system is too high, PureBallast’s control valve V201-8 will
close to reduce flow. If the V201-8 closes more than a parameter set degree,
the control system sends a signal requesting the ballast pump to reduce the
speed (and so the flow). When the flow is reduced, V201-8 can open.
Valve V201-8 operates (open/closes) in a range between a parameter set
value (p157) and 100 %, where default is 70 %. Within this range, flow is
regulated by V201-8 without cavitation.
Preparations and conditions
• This operation requires login level AlfaLaval.
Follow the steps below:
1. Start a ballast process. Wait until the system is in mode Full ballast. Listen
for cavitation noises at V201-8.
If cavitation, go to step 2. It not, go to step 5.
2. Go to page 5.1 Main parameters .
3. Increase parameter p157 in steps of 5 % at a time. After each change, wait
until the parameter change take effect (a couple of minutes). Listen for
cavitation noises at V201-8.
Note: The effect can not be observed during backflush, since the external
feed function is disabled.
200000695-1-EN-GB 94
3 Operating instructions and control system description EN