Marine Engineering Study Materials

MEO Class 2 Orals Questions and Answers Part 2

What is static stability?

• It is defined as the ability of a ship to regain its upright equilibrium position, after the removal of external factor which caused the vessel to heal at an angle.
• It gives the stability information of a vessel under the condition that the outside water is static.
• It is expressed in terms of metacentric height, GM (for angle of heel up to 10 degrees) and righting lever, GZ (for angle of heel above 10 degrees)
• Its unit is meter.
• Static stability at two different angle can be same.

What is dynamic stability?

• It is defined as the energy required in heeling the ship from upright equilibrium till the angle of heel in question.
• It gives the stability information of a vessel considering dynamic behavior of the sea.
• It is expressed in terms of area under righting moment curve or GZ curve.
• Its unit is meter-radians.

What is combustible gas detectors or explosimeter?

• An explosimeter is a device used to detect the amount of combustible gases present in a sample of the given atmosphere.
• This gives reading in terms of percentage of the lower flammable limit or LFL.
• The working principle of explosimeter is, resistance proportional to heat.
• The equipment consist of a wheatstone bridge with one resistance as variable.
• It can only be used if gas content is very low.

What is tankscope?

• A tankscope is a device used for measurement of hydrocarbon gas content in a sample of given atmosphere.
• This is meant for measuring hydrocarbon vapours in inerted atmospheres.
• The reading is only percentage of the volume of the hydrocarbon vapour.
• The principle is that, there is an alteration in the temperature of the heated filament which enhances the change of resistance.

How multi gas detectors work?

• Multi gas detectors are used to detect only targeted gases and vapours.
• It is very specific to that gas only.
• It consist of a portable bellow pump and detector tubes.
• The detector tube is like a vial filled with reagent that will react with the specific chemical.
• If the atmosphere contain that specific gas or vapour, colour of the tube changes.
• The length of the colour is read from the tube for amount of gas present.

What is MOB or Man Overboard Marker?

Man overboard marker is a device fitted on the outboard side of ship’s bridge wing attached to a life buoy. If any crew member or passenger falls overboard, personnel onboard will quickly release the MOB marker which will fall into sea and float, emitting orange smoke and flashing lights. The purpose of man overboard marker is to mark the position of the person fallen overboard for rescue operation. Once released, the MOB marker will float in sea attached to the life buoy and produce dense orange smoke for at least 15 minutes and two lights will burn for at least 2 hours as a day and night signal. SOLAS require MOB marker be able to be operable from a mounting height of at least 30 meters. Potassium chromate is the main ingredient of MOB marker. Chemical reaction of potassium chromate with other ingredients inside generates the dense orange smoke.

What is VGP or Vessel General Permit?

• It is National Pollutant Discharge Elimination System (NPDES) permit.
• It is issued by the US Environmental Protection Agency (USEPA) as a result of federal court ruling.
• It establishes permit limits and conditions on 26 waste water discharges incidental to the normal operation of vessels that were previously exempted by the USEPA.
• It prevent discharges to the US inland waters such as rivers, lakes, streams, etc.
• Waste water includes bilge water, ballast water, anti fouling hull coating, AFFF, boiler blow down, chain locker effluent, distillation and reverse osmosis brine, elevator pit effluent, etc.

MEO Class 2 Orals Questions and Answers Part 2