Short notes of MGPS | ETO ORAL

 

MGPS – Marine Growth Prevention System

The seawater system is protected against fouling by the anti-fouling system.

The system protects against marine growth and corrosion by passing an electric current through anodes placed at the seawater intakes.

The marine growth protection anodes (Cu) are made from copper and the trap corrosion anodes (Al) are made from aluminium alloy. The anodes are fitted in the suction strainers.

The port and starboard side strainers each have two MG anodes and two TC (Trap corrosion) anodes.

A low current must be maintained at the sea suction strainer which is not operating.

Working of MGPS

MGPS is based on the electrolytic principle and consists of copper, and aluminium anodes

Reaction at copper Anode:

The Cu anodes release copper ions when an electric voltage is applied. These Cu ions combine with oxygen in the water to form cuprous oxides which have a strong toxic effect on marine organisms which enter the system, thereby minimizing their growth and fouling of the seawater system. 

Anode reaction	Cu   →   Cu2 +   + 2e-
Cathodic reaction	3 H2O + 2e-   →  H2 + 2OH-
Colloid formation	Cu2+ + 2OH-   →    Cu2O

Reaction at Aluminium Anode:

The TC anodes form aluminium hydroxide when an electric current is applied. This forms an anti-corrosion barrier on the steel pipework of the seawater system.

 

Anode reaction	Al   →   Al 3 + 3e-
Cathodic reaction	3 H2o + 3e-      →   3/2H2 + 3OH-
Colloid formation	Al3+ + 3OH-      →   Al(OH)3

General Specifications of MGPS 

Power supply: 220VAC 60 Hz Maximum output 20A DC

Anodes: Copper (Cu) and Aluminum (Al)

What is the life of MGPS anodes?

Anode life is approximately 2.5 years.

Effects of low Current settings

Too low a current results in insufficient protection.

Effects of High current settings

Too high a current results in rapid wasting of the anodes.

Higher currents than necessary will result in the rapid depletion of the anodes and the system will not be protected when the anodes have wasted away.

The rapid depletion of the copper anodes can result in the deposition of the copper on the suction strainer causing partial blockage of the strainer. The condition of the strainers and the anodes should be checked at six-monthly intervals to ensure that this depletion is not taking place.

When do we have to reduce the Anode current?

If the seawater flow rate is reduced from this value the current applied to the anodes should also be reduced.

Incorrect the setting of the current can result in inadequate protection against marine growth and corrosion.

Adjustment of current should only be made after consulting the Maker or Operating Manual.

What is the operating current of MGPS Anode?

Generally,

Anode	In operation current	Not operating current
Al Anode	3.3 A	0.05 A
Cu Anode	1.7 A	0.05 A

A low current must be maintained at the sea suction strainer which is not operating. 

It is essential that the correct current is always applied to the anodes at the operating sea water suction chest as the maker advises.

Which of the anodes decomposes faster?

Copper (Cu) anode.

What is electrolysis?

Electrical current flow through the liquid causes a chemical reaction.

What is the concentration of copper?

concentrations of copper are extremely small -less than 2 parts per billion

Maintenance

Check the current readings and note them down every day.

The anodes must be checked periodically in order to ensure that they are wasting at the expected rate.