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Anti-Fowling
Anti-fowling is the process of eliminating obstructive organisms from essential components of seawater systems. Marine organism grow and attach to the surfaces of the outboard suction inlets used to obtain water for cooling systems. Electro-chlorination involves running high electrical current through sea water. The combination of current and sea water alters the chemical composition to create sodium hypochlorite to purge any bio-matter. An electrolytic method of anti-fowling involves running electrical current through two anodes (Scardino, 2009). These anodes typically consist of copper and aluminum (or iron). The copper anode releases its ion into the water creating an environment that is too toxic for bio-matter. The second metal, aluminum, coats the inside of the pipes to help prevent corrosion. Other forms of marine growth such as muscles and algae may attach themselves to the bottom of a ships hull. This causes the ship to have a less hydrodynamic shape since it would not be uniform and smooth around the hull. This creates the problem of less fuel efficiency as it slows down the vessel (IMO, 2018). This issue can be remedied by using special paint that prevent the growth of such organisms.

Industry Growth
     Marine engineering is predicted to grow approximately 12% from 2016 to 2026. Currently there are about 8,200 naval architects and marine engineers employed, however, this number is expected to increase to 9,200 by the year 2026 (BLS, 2017). This trend could be attributed to the demand in fossil fuels obtained through offshore drilling and mining. In addition, 90% of the worlds trade is done overseas by a close to 50,000 ships, all of which requiring engineers aboard and shore side (ICS, 2017).

Stability
Engineers also face the challenge of balancing cargo as the mass of the ship increase and the center of gravity shifts higher as additional containers are stacked vertically. In addition, the weight of fuel presents a problem as the pitch of the ship cause the weight to shift with the liquid causing an imbalance. This offset is counteracted by water inside larger ballast tanks. Engineers are faced with the task of balancing and tracking the fuel and ballast water of a ship.

Corrosion
    Corrosion can be inhibited through cathodic protection by utilizing sacrifice anodes. A piece of metal of metal such as zinc, is used as the sacrificial anode as it becomes the cathode in the chemical reaction. This causes the metal to corrode and not the ship’s hull. Another way to prevent corrosion is by sending a controlled amount of low DC current to the ship’s hull to prevent the process of electro-chemical corrosion. This changes the electrical charge of the ship’s hull to prevent electro-chemical corrosion.

Sulfur Emission
The burning of marine fuels has the potential to release harmful pollutants into the atmosphere. Ships burn marine diesel in addition to heavy fuel oil. Heavy fuel oil, being the heaviest of refined oils, releases sulfur when burned. Sulfur emission have the potential to raise atmospheric and ocean acidities causing harm to. However, heavy fuel oil may only be burned in international waters due to the pollution created. It is commercially advantageous due to the cost effectiveness compared to other marine fuels. It is prospected that heavy fuel oil will be phased out of commercial use by the year 2020 (Smith, 2018).

Oil and Water discharge
     Water, oil, and other substances collect at the bottom of the ship in what is known as the bilge. Bilge water is pumped over board, however, must pass a pollution threshold test of 15ppm (parts per million) of oil to be discharged. Water is tested and either discharged if clean or recirculated to a holding tank to be separated before being tested again. The tank it is sent back to, oily water separator, utilizes gravity to separate the fluids due to there viscosity. Ships over 400 gross tons must are required to carry the equipment to separate oil from bilge water. Furthermore, as enforced by MARPOL, all ships over 400 gross tons and all oil tankers over 150 gross tons are require to log all oil transfer is an oil record book (EPA, 2011).

Cavitation
Cavitation is another challenge marine engineers are pitted with. Cavitation is the process of forming an air bubble in a liquid due to the vaporization of that liquid cause by an area of low pressure. This area of low pressure lowers the boiling point of a liquid allowing it to vaporize into a gas. Cavitation can take place in pumps which could cause damage to the impeller that moves the fluids through the system. Cavitation is also seen in propulsion. Low pressure pockets form on the surface of the propeller blades as its revolutions per minute increase (IIMS, 2015). Cavitation on the propeller causes a small put violent implosion which could warp the propeller blade. To remedy the issue, more blades allow the same amount of propulsion force but at a lower rate of revolutions. This is crucial for submarines as the propeller needs to keep the vessel relatively quiet to stay hidden. With more propeller blades, the vessel is able to achieve the same amount of propulsion force at lower shaft revolutions.

Bureau of Labor Statistics (2017, Oct. 24) Occupational Handbook: Marine Engineers and Naval Architects www.bls.gov/ooh/architecture-and-engineering/marine-engineers-and-naval-architects.htm#

Environmental Protection Agency Office of Wastewater Management Untied States (2011) Oily Bilgewater Separators https://www3.epa.gov/npdes/pubs/vgp_bilge.pdf

International Chamber of Shipping (2017) Shipping and World Trade, http://www.ics-shipping.org/shipping-facts/shipping-and-world-trade

International Maritime Organization (2018) Anti-Fouling systems  http://www.imo.org/en/OurWork/Environment/Anti-foulingSystems/Pages/Default.aspx 

International Institute of Maritime Surveying (2015) An Introduction to Propeller Cavitation

https://www.iims.org.uk/introduction-propeller-cavitation/

Scardino, A.J., Fletcher, L.E., Lewis, J.A. (2009) Fouling control using air bubble curtains: protection for stationary vessel. Journal of marine engineering and technology, 8(1), 3-10. https://doi.org/10.1080/20464177.2009.11020214

Smith C. (Feb. 21, 2018) Eco Ships:The New Norm for Top Tier Ships, Maritime Reporter and Engineering News, 80(2). www.maritimepropulsion.com