Sea water contains both macro and micro marine organisms such as sea worm,
molluscs, barnacles, algae, hard shells like acorn barnades etc. These organisms
stick to the surface of the ship and flourish over there, resulting in marine growth.
Effects of Marine Growth
The fouling problem arises when barnacles, mussels and other lower forms of
marine life as larvae enter pipework systems and settle on the internal surface of
pipes where they rapidly grow and multiply.
In the most extreme cases, complete seawater lines can become blocked,
affecting the safety and operational capability of the ship. In other instances, the
gradual restriction in the flow of seawater through cooling systems can impair
engine efficiency, leading to increased fuel usage.
As the marine organisms flourish they block and narrow the passage of cooling
water in the ship’s system resulting in the following factors:
– Impairing the heat transfer system.
– Overheating of several water-cooled machineries.
– Increase in the rate of corrosion and thinning of pipes.
– Reduced efficiency which can lead to loss of vessel speed, increase fuel uses
and loss of time.
Without MGPS With MGPS
Image Credit: Iccp-mgps.com
Fighting Marine Growth:
To avoid formation of marine growth MGPS or marine
growth preventive system (MGPS) is used onboard ship.
Image Credit: Iccp-mgps.com
Fig: MGPS in Engine room sea water system
Marine Growth Protection System (MGPS)
• MGPS is based on the electrolytic principle and consists of copper,
aluminium and ferrous anodes which are fed with an impressed electrical
current from a control panel.
• The anode are usually mounted in pairs in the ship’s sea chest or strainer
where they are in direct contact with the flow of water entering the
seawater lines. Also the anodes can be mounted on independent treatment
tank for other convenience.
• In operation, the copper anode produces ions which are transported by the
seawater and carried into the pipework system and equipment beyond.
• Although the concentrations of copper in solution are extremely small i.e.
less than 2 parts per billion they are sufficient to prevent marine life from
setting and multiplying.
• At the same time, the slow dissolution of the aluminium / ferrous anode
produces ions which spread throughout the system and produce an anti-
corrosive layer on the internal surface of pipes.
MGPS- Chlorination System
• This system is designed to prevent the adhesion of marine
growths to the internal pipe line of ships through the chemical
reaction of chlorine compounds which are produced through the
electrolyzation of sea water.
• First, the sea water taken out of the outlet of one of the common
sea water pumps or the pump for exclusive use in MGPS is led
into the Generating Chamber, in which the sea water is
electrolyzed with specially designed electrodes. Then the sea
water containing chlorine compounds is injected into scoop or
sea chests through the nozzles to mix with the sea water sucked
in from outside of the ship, thus preventing marine growths from
adhering to the interior of the ship's sea water line including sea
chest, piping and heat exchanger.
How it works:
- The anti-fouling process is based on the electrolysis of part
of the sodium chloride (NaCl) contained in sea water. The
electrolysis is obtained by passing the sea water through a
generating chamber containing electrode(Ti anode).
- The chemical and electrochemical reactions which occur in
the generating chamber are as follows:
1) at the anode free chlorine is formed
2 Cl ⇔ Cl₂ + 2e-
2) at the cathode OH-ions are formed
2 H2O + 2e- ⇔ 2 OH-+ H3
3) around the anode the OH- ions react with the Na+ ions
and Cl2 to produce sodium hypochlorite
2 NaOH + Cl₂ ⇔ NaOCl + NaCl + H2O
- Alongside these principal reactions which bring about the
production of sodium hypochlorite, secondary reactions
occur due to the actions which are present in sea water
such as calcium and magnesium, forming hydrates and
- The sodium hypochlorite solution leaving the generating
chamber is piped to the chlorine injection points situated
on the sea chests to be mixed with the incoming sea
- Then the chlorine-active contained in the solution
oxidizes the organic substances found in sea water.
- The adult organisms, for example mussels, are able to
resist the effects of chlorine-active by closing themselves
inside their shells. However unable to feed they will not
settle in an environment where chlorine-active is present.
Effects of Chlorine
• Chlorine is a well known toxicant. It has been shown that
0.2 to 0.5 PPM of continuous chlorination will prevent all
marine fouling in time. Higher than 0.5 PPM might
produce the corrosion of the metallic piping, and other
• A trace residual discharge will insure the killing of all
fouling organisms in a sea water system when constant
chlorination is employed. It should be emphasized that
constant chlorination is the best method for safe and
efficient fouling and bacteria control.
Advantages of Using MGPS
1. Based on the electrolytic principle, providing continuous and
reliable protection from marine growth without the use of chemicals.
2. A dual system combining pipework anti-fouling and corrosion
3. Environmentally safe. Meets all environmental protection standards
4. Reduces energy consumption
5. Maintains plant and equipment at high efficiency
6. Reduces cleaning costs of pumps, pipes, valves, sea chests,
gratings, heat exchangers, etc.
7. Improved heat transfer in heat exchangers
8. Increases life span of plant and equipment
9. Provides continuous maintenance free protection for years
10. Lower capital and operating costs than any competing technology
4. Marine Auxiliary Machinery, Seventh Edition
Paperback by H D Mc George
4. General Engineering Knowledge for Marine