Marine Growth Prevention System (MGPS) prevents marine growth from
accumulating. In the seawater cooling systems to keep the piping clear of bio-fouling.
Marine growth results from the settlement of larvae and subsequent marine life
forms, in particular hard shells such as acorn barnacles and gooseneck barnacles. In
extreme cases, marine growth fouling can become so serious as to completely
obstruct the flow of seawater through cooling piping. Lesser cooling system
complications include overheating, reduced efficiency, and increased corrosion.
7.11.1 Structure and Principle of Operation
The system is designed to prevent adhesion of marine growths to the interior of the
sea water lines system of the ship through the chemical reaction of chlorine
compounds which are produce through electrolization of the sea water.
The sea water from the delivery of the sea water pump i.e, main cooling s.w. pump,
is led into the electrolytic cell and in which electrolyzed by the electrodes. The sea
water that electrolyzed containing chlorine compounds is injected through nozzles
into the sea chests (high and low sea chest, emergency fire pump sea chest, etc.,)
to mix with the sea water coming from outside of the ship and thus preventing the
adhesion of the marine growths in the piping’s and coolers.
7.11.2 Parts of Marine Growth Prevention System
a. Rectifier (Power Supply)
A galvanostatic silicon rectifier under SCR control that convert A.C. to D.C.
indispensable for electrolysis.
Electrolysis is a method of separating chemically bonded elements and
compounds to sea water by passing an electric current through them.
b. Electrolytic Cell
Housed in the same casing with the rectifier and consists of Anode (Pt-plated Ti
Anode) and cathode (mild steel) to generate chlorine compounds through the
electrolization of sea water (in case of Nippon Corrosion Engineering).
c. Flow Meter
A Differential Pressure Type Flow Meter with a built in micro switch is used to
monitor the flow rate of the sea water into the electrolytic cell. It has an interlock
connection to the rectifier that in case the sea water flow rate is not sufficient, the
rectifier will automatically shutdown by the used of the signal coming from the
micro switch.
Another flow meter is connected into the outlet of the electrolytic cell to function
as monitor for adequate distribution of electrolyzed sea water into the respective
sea chest with any interconnection with the rectifier.
d. Injection Nozzle
Each sea chest is equipped with injection nozzle/s through which the sea water
containing chlorine compound is injected evenly into the respective sea chests.
7.11.3 Operation Procedures (MGPS TD-800P)
a. Open the ship side valves for the sea chest to be used and the MGPS valves
(s.w. supply valve from s.w. pump, inlet & outlet valve for flow meter and the
electrolytic cell and the distribution valves to sea chest to be used).
b. Check the “setting needle” (red) of flow meter on the inlet of the cell and make
sure it is set to the correct value about 5~7m3/hr.
c. Operate s.w. pump and make sure that the sea water flow into the cell is not less
than 7m3/hr as the specified flow rate in the “Operation Plan”.
d. Operation with the Rectifier panel:
i. Turn the “Output Adjust “knob of D.C. output voltage regulator counter-clockwise
and set to lowest output setting.
ii. Switch on the NFB A.C. input switch and make sure the pilot lamp source(ivory)
indicator is lit.
iii. Turn “Start-Stop” Change-over switch to “Start” position and check the pilot lamp
source (green) is lit. The rectifier is now in operation.
iv. Turn “Output Adjust” knob of D.C. output voltage regulator to set the operation
current as per the “operation plan”.
Note: When turning “Output Adjust” knob of D.C. Output Voltage Regulator:
1. counter clockwise – amperage and voltage decreases
2. clockwise – amperage and voltage increases.
v. Check the MGPS condition and ensure that the operation parameters are in
accordance to the “Operation Plan”.
vi. Carry out proper “Daily Log” for the operation parameters for future reference.
Precautions:
a. In case that the sea water flow rate to the electrolytic cell drops below the set
value in the flow meter, the operation of the MGPS rectifier will automatically shut
down and the green lamp indicator will be off. When the flow rate has increased
above the set value, the operation of the MGPS will automatically start again.
Always check the sea water flow rate condition and the MGPS operation panel
that it is with accordance to the operation plan.
b. Adjust the distribution valve on the outlet of electrolytic cell for even distribution of
sea water flow at the sea chest by observing the respective flow meter.
c. Check the chlorine compounds condition of the sea water by means of the
“residual chlorine tester” and follow the operation plan.
d. Adjust the operating current as per ship condition, i.e., at sea, in port, etc., and in
accordance to the operating plan.
vii. In case the operation of the MGPS will be stopped;
a. Turn the “Adjust Knob” of the D.C. voltage regulator counter-clockwise to full and
switch of the power.
b. Close all the valves for the MGPS and sea water lines.
c. Drain the electrolytic cell by opening the drain valve at the bottom of the casing.
