Proceedings magazine is a communication tool for the Coast Guard's Marine Safety & Security Council. Each quarterly magazine focuses on a specific theme of interest to the marine industry.
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80 Proceedings Winter 2013–2014 www.uscg.mil/proceedings Engineering A nswers 1. Note: The quality of the spray pattern produced by a diesel engine fuel injection nozzle is primarily a function of the following: the viscosity of the fuel passing through the nozzle orifces, the pressure of the fuel behind the nozzle orifces, and the geometry of the orifces themselves. A. incorrect fuel rack setting Incorrect answer. An incorrect fuel rack setting results in a change of the overall quantity of fuel injected into the engine cylinder by the fuel injection nozzle. This has no impact on the rate of injection or the quality of the spray pattern. B. overcooling of the nozzle Correct answer. When the injector nozzle is overcooled, the temperature of the fuel passing through the nozzle orifces is lowered, which results in an increase in fuel viscosity. The higher viscosity fuel results in improper fuel atomization, which impacts the quality of the spray pattern. C. low fring pres- sure Incorrect answer. An incorrect spray pattern may possibly result in low fring pressure, but low fring pressure is not a direct cause of an incorrect spray pattern. D. excessive lube oil temperature Incorrect answer. Excessive lube oil temperature certainly has a negative impact on the characteristics of cylinder lubrication, but this does not have a direct impact on fuel injector nozzle spray patterns. 2. Note: An impressed current cathodic protection system is utilized to maintain continuous protection of the hull without sacrifcial corrosion of the anodes. A. The anodes are connected to the hull and waste away with time. Incorrect answer. This type of protection is associated with the use of zinc anodes bonded to the hull which are sacrifcial (waste away with time) and require periodic replacement to maintain protection of the hull. There is no impressed current with this method of protection. B. The anodes are insulated from the hull and do not waste away with time. Correct answer. Anodes that are attached to but insulated from the hull are associ- ated with an impressed current cathodic protection system. Such anodes are not sacrifcial and will not waste away with time. C. The anodes are connected to the hull and do not waste away with time. Incorrect answer. Anodes that are bonded to the hull are sacrifcial and will waste away with time. D. The anodes are insulated from the hull and waste away with time. Incorrect answer. Anodes that are attached to but insulated from the hull are used in an impressed current cathodic protection system and do not waste away with time. 3. Note: Fixed CO 2 extinguishing systems can either be manually deployed or automatically activated depending upon the application. A. machinery space Incorrect answer. A fxed CO 2 extinguishing system used to protect a machinery space, such as an engine-room, is a total-fooding system. This system is always deployed manually and only after ascer- taining that all personnel have been evacuated from the machinery space. B. paint locker Correct answer. Smaller systems (using less than 300 lbs. of CO 2 ) used to protect a paint locker may be either manually deployed or automatically activated. C. cargo hold Incorrect answer. The cargo hold fxed fre CO2 system is activated in much the same way a machinery space total-fooding system is activated. After sealing the hold, the system is deployed manually. D. all the above Incorrect answer. Choice "B" is the only correct answer. 4. Note: The pertinent regulations are found in Subchapter F, Marine Engineering. In searching the Subchapter F index, it is found that the regulations for refrigeration machinery are found in Subpart §58.20. In searching Subpart §58.20, it is found that the regulations pertaining to pressure relieving devices are found in §58.20-10. A. The relief valve from the receiver must relieve to the condenser frst. Incorrect answer. The relief valve from the receiver may relieve to the con- denser frst before relieving to the low side or the atmosphere. However, the relief valve may either relieve directly to the atmosphere or to the low side before relieving to the atmosphere. See §58.20-10(b). B. The relief valve setting shall be 1 ¼ times the maximum allowable working pressure. Incorrect answer. The relief valve shall be set to a pressure not greater than the maximum allowable working pressure. See §58.20-10(a). C. A rupture disc may be ftted in series with the relief valve. Correct answer. A rupture disc may be ftted in series with the relief valve as long as the bursting pressure is no higher than the relief valve pressure relief setting and that the relief valve is of a type not affected by back pressure. See §58.20-10(b). D. The rupture disc shall burst at a pressure not higher than 10% above the relief valve setting. Incorrect answer. When piped in series with a relief valve, the rupture disc shall burst at a pressure no higher than the relief valve pressure relief setting. See §58.20-10(b). Winter �2013_45.indd 80 2/10/14 9:32 AM