5. ACCIDENTES MARITIMOS
5.4 ANÁLISIS DE SINIESTROS Y/O SUCESOS
stages of a flash type evaporator would indicate __________.
3193 Fluctuations in the pressure and temperature of the steam supplied to the first-effect of a low pressure submerged tube distilling plant will cause ___________.
A. chill shocking is necessary to remove scale A. increased heat levels throughout the entire unit B. leakage at the second-stage condenser B. decreased priming and lower salinity distillate C. faulty operation of the brine overboard pump C. first effect scale formation to be loosened
D. carryover in the first-stage D. pressure and temperature fluctuations in the entire unit
Ans: D Ans: D
3194 Which of the following descriptions best identifies the operating principal of a flash-type evaporator?
3195 Which of the listed problems could produce a high absolute pressure within a flash type evaporator?
A. Sea water is heated to boiling temperature while under a vacuum. A. production of high salinity distillate
B. Sea water is passed over heated plates in a thin film. B. seawater feed temperature below 75°C C. Heated sea water is injected into a vacuum chamber. C. a leak in the first stage demister D. Sea water is forced through a heated eductor. D. a cracked distillate pump vent line
Ans: C Ans: D
3196 One advantage of a triple-effect low pressure submerged tube distilling plant over a double-effect unit is _____________.
3197 A salinity indicating system functions on the basic principle of measuring the _____________.
A. better water purity A. electrical inductance of water
B. less scale formation B. electrical conductivity of water
C. less internal corrosion C. specific gravity of water
D. greater evaporator efficiency D. hydrogen ion concentration of water
Ans: D Ans: B
3198 One distinct advantage of flash type evaporators, as compared to most other evaporators, is that in a flash evaporator ________.
3199 Early models of the flash-type evaporators used a separate shell-and-tube heat exchanger as the air ejector condenser. More recent models use a combined air ejector condenser with the
____________.
A. high temperature distillate can be recirculated to induce additional flashing
A. distilling condenser
B. scale formation is not a severe problem B. salt water feed heater
C. cold shocking is more effective in removing scale C. distillate cooler D. water purity is greatly increased at high capacity D. flash chamber
Ans: B Ans: B
3200 If the supplied steam pressure to the first effect of a submerged tube distilling plant is allowed to fluctuate, the distiller
_________________.
3201 Fluctuating pressures and temperatures in an evaporator will _____________.
A. solenoid dump valve will trip A. eliminate most of the scale formation in the first effect B. air ejector will operate erratically B. increase the heat level in all effects
C. water levels will automatically lower C. increase the probability of priming
D. brine density will increase D. automatically cold shock the evaporator
Ans: A Ans: C
3202 The temperature of the steam flow to the saltwater feed heater, in a flash type evaporator can be manipulated by a/an
____________.
3203 In a two stage flash evaporator, heated feedwater is vaporized in the _____________.
A. pressure regulator within the supply orifice A. feed inlet box
B. thermally actuated bypass valve B. distiller feedwater heater
C. attemporator in the steam supply piping C. first and second stage flash chambers D. sensor wired in with the three-way salinity dump valve D. first and second stage vapor separators
Ans: C Ans: C
3204 Excessive scale formation in a distilling plant may result from ____________.
3205 A vacuum is initially created in a flash type distilling plant by _________.
A. poor distillate quality A. the flashing of the feed water
B. reduced evaporator capacity B. the condensation of the saltwater feed
C. low brine concentration C. air ejectors, eductors, or a separate vacuum pump
D. improper vacuum regulation D. condensation of the distillate
Ans: D Ans: C
3206 While at sea, the flash type evaporator is discharging the output to the distill tanks. If it becomes necessary to reduce the feed water temperature below 74°C, you should ____________.
3207 If a flash-type evaporator was designed to operate in seawater at 24°C, and the current seawater temperature is 10°C, without readjusting any valve associated with this evaporator, ___________.
A. continue the current evaporator operation A. the capacity will be doubled
B. dump the evaporator to the bilge B. the capacity will remain the same regardless of the seawater temperature
C. secure the evaporator until the feedwater temperature can be raised to 74°C or more
C. it will probably "trip off the line" as a result of an excessive and violent rate of flashing
D. raise the tripping point at the salinity indicating panel for the three-way valve
D. it will produce the purest and lowest salinity concentration of distillate that can be produced
Ans: A Ans: C
3208 Where auxiliary steam supply is not used in the process of maintaining vacuum in a distilling unit, the vacuum is usually attained by ________.
3209 In the event of a power failure to the salinity panel on a flash-type evaporator, the three-way solenoid valve will _____________.
A. air operated air ejectors A. be frozen in its last position
B. vacuum pumps B. direct distillate to the fresh water tank
C. increasing the rate of condensation in the distiller condensers C. dump distillate to the bilge
D. a separate suction connection to the brine overboard pump D. dump distillate to the makeup feed tank
Ans: B Ans: C
3210 The absolute pressure maintained in the shell of the salt water feed heater on most flash evaporators used on steam propelled vessels is __________________.
3211 Condensate formed within the first-effect tube nest of a double-effect, low pressure evaporator, is removed by a _______.
A. slightly less than the absolute pressure of the L.P. extraction A. series of baffles B. slightly less than the supplied live steam pressure at the reducing
valve outlet
B. crossover pipe
C. slightly higher than the second stage vacuum C. condensate separator
D. slightly lower than the first stage vacuum D. drain pump
Ans: A Ans: D
3212 Steam supply for the operation of the low pressure evaporators may be obtained directly from the ________.
3213 The brine level in the second-stage of a flash-type evaporator is due in part to the feed rate, the rate of evaporation in both stages, and the _____________.
A. main steam line A. steam flow rate to the air ejectors
B. turbine extraction line B. float controlled level of the feed heater
C. turbo-generator steam supply line C. capacity of the distillate pump
D. air ejector exhaust line D. throughput of the brine overboard pump
Ans: B Ans: D
3214 Fluctuations in the pressure and temperature of the steam supplied to the first-effect of a low pressure distilling plant will cause _____________.
3215 A fixed orifice plate is generally installed in the live steam supply to an evaporator. One of the functions of this orifice is to control the quantity of the supplied steam. A second function is to ____________.
A. increased heat levels throughout the entire unit A. reduce pressure fluctuations from occurring in the steam supply to the salt water feed heater
B. decreased priming and lower distillate salinity B. produce more useful superheated supply steam C. first effect scale formation to be lessened C. guarantee that the steam supply will remain desuperheated D. pressure and temperature fluctuations in the entire unit D. produce a low salt water feed heater shell absolute pressure
Ans: D Ans: A
3216 When securing a centrifugal distillate pump, which of the listed steps should be carried out FIRST?
3217 A vacuum is initially established in the first and second stages of a low pressure evaporator by the use of _________.
A. Stop the pump. A. vacuum drag from the auxiliary condensate system
B. Close the pressure gage valves. B. individual vacuum pumps
C. Trip the three-way solenoid valve. C. a single non-condensing air ejector
D. Close the sealing line valves to the pump. D. a two stage air ejector
Ans: C Ans: D
3218 The vapor separators installed in some distilling plants consist of several rows of vertical hooked vanes which remove entrained moisture from the vapor by _____________.
3219 Where a two-stage air ejector set is used in a two-stage flash evaporator, the first-stage air ejector takes suction from the second stage of the evaporator, and the second stage air ejector _____________.
A. directing the vapor through a fine metallic mesh A. takes suction from the first stage of the evaporator B. condensing water droplets on the metal vanes B. takes suction from the second stage of the evaporator as well
C. trapping water droplets in the metallic mesh C. takes suction from the first stage ejector discharge D. abruptly changing the direction of vapor flow D. is normally idle and used mainly as a standby unit
Ans: D Ans: C
3220 When the steam leaving the control orifice of the live steam supply is not conditioned, the evaporator _____________.
3221 A flash type evaporator is designed to operate in 24°C sea water, if operated in 10°C sea water, ________.
A. capacity will be increased A. the absolute pressures will be slightly below the predicted design absolute pressures
B. capacity will be decreased B. absolute pressure in the evaporator stages will be higher C. salt water feed heater absolute pressure will decrease significantly C. the unit will operate at reduced capacity
D. salt water feed heater absolute pressure will increase significantly D. thermal efficiency will decrease, but brine density will increase
Ans: B Ans: A
3222 In order to prevent salt water contamination of the distillate in a flash-type evaporator, it is important to provide a positive seal around the _____________.
3223 Which of the following statements describes the proper operation of a three-way solenoid trip valve on a flash-type evaporator?
A. spray caps A. The valve must be manually reset.
B. demisters B. The valve will trip if the sea water feed temperature drops below
79°C.
C. saltwater heater vents C. The valve is interlocked to trip only on de-energization of the
solenoid.
D. steam supply orifice plate D. The valve will trip if the distillate is too warm.
Ans: B Ans: A
3224 Where would a salinity cell be installed in a double-effect distilling plant?
3225 The purpose of chill shocking an evaporator is to _________.
A. Distillate pump discharge A. prepare for a hydrostatic test
B. Tube nest drain pump discharge B. stress relieve the tubes
C. Air ejector condensate drain C. break loose scale deposits formed on the tubes
D. All of the above D. test for leaks in the tubes
Ans: D Ans: C
3226 Which of the listed problems is occurring if a coil type high pressure evaporator constantly requires an increase in the coil steam pressure in order to maintain capacity?
3227 In the last effect of a multi-effect submerged tubedistilling plant rapid fluctuations of the absolutepressure tend to cause _____________.
A. The brine density is improper. A. scale formation with increased heat transfer
B. Heat transfer surfaces are being layered with scale. B. priming with increased salinity of distillate C. Impure distillate is being produced. C. slight foaming at the distillate feed pump D. Shell vapor pressure is constantly decreasing. D. improved operating conditions at the brine pump
Ans: B Ans: B
3228 In which of the following types of evaporators is the control of brine density least important?
3229 A multistage flash evaporator will be unable to produce consistently pure distillate if the __________________.
A. Solo shell evaporators A. distillate cooler is dirty
B. Flash evaporators B. tubes of the saltwater feed heater are flooded internally
C. Submerged tube evaporators C. distillate meter stops
D. Basket evaporators D. vacuum is fluctuating
Ans: B Ans: D
3230 When securing a centrifugal type distillate pump, which of the listed steps should be carried out first?
3231 Rapid fluctuation of the last effect shell vacuum in a submerged tube evaporator can cause _____________.
A. Close the pressure gage isolation valves. A. erratic air ejector operation
B. Secure the casing vapor vent line. B. air leaks in the tube nest
C. Secure the stuffing box sealing water line. C. rapid scaling in all effects
D. Trip the three way dump valve. D. priming in that effect
Ans: D Ans: D
3232 Improper waterside venting of the tube nests in a submerged tube evaporator will cause a/an _____________.
3233 If a higher than normal water level is observed through the inspection port of a flash evaporator, you should suspect ______________.
A. fluctuating vacuum in the evaporator A. a leak in the feedwater heater
B. loss of evaporator capacity B. improper vacuum
C. increased vacuum in the first effect C. a malfunctioning brine pump
D. increased brine overboard flow rate D. a clogged desuperheater water strainer
Ans: B Ans: C
3234 Indicated high salinity of the distillate discharged from a flash-type distilling plant will be a result of ___________.
3235 In a flash evaporator, scale as a result of higher than normal temperatures is most likely to occur in the ________.
A. maintaining the proper distilling plant heat balance A. second stage feed heater
B. carrying the brine level below normal B. saltwater feed heater
C. leaks in the demister baffles C. distillate cooler
D. venting of the saltwater heater drain pump D. second stage vapor separator
Ans: C Ans: B
3236 Irregular feeding or surging of the feedwater supply to a flash evaporator may be attributed to ______________.
3237 If the orifice in the loop seal of a flash evaporator were to become significantly enlarged through erosion, the ________.
A. erratic water flow through the air eductor A. distillate produced in the second stage would flow towards the first stage
B. a clogged vent line from the air eductor condenser B. evaporator absolute pressure would eventually equalize in both stages to that of the first stage
C. excessive pressure in the seawater feed heater C. evaporator absolute pressure could eventually equalize in both stages to that of the second stage
D. a dirty strainer in the saltwater feed pump suction line D. salt water feed heater absolute pressure would increase to that of the evaporator second stage
Ans: D Ans: C
3238 In a flash evaporator, heated water under pressure is converted into vapor by suddenly ____________.
3239 Which of the following statements represents the basic principle of operation of an electrical salinity indicator?
A. increasing its temperature A. Measures the hydrogen ion concentration.
B. increasing its velocity B. Measures the electrical resistance of the water.
C. decreasing its density C. Determines the conductivity of the dissolved oxygen.
D. decreasing its pressure D. Measures the voltage of the chloride ions.
Ans: D Ans: B
3240 In a double-effect submerged tube evaporator, the brine density should be prevented from falling below 1.5/32nds to minimize ____________.
3241 Vapor is produced in a flash evaporator by introducing _______________.
A. scale formation on the tube nests A. steam through heating coils
B. loss in capacity and maintain plant efficiency B. steam through cooling coils
C. corrosion in the evaporator C. heated water into a high pressure area
D. carryover in the evaporator D. heated water into a low pressure area
Ans: B Ans: D
3242 A fluctuating and unsteady vacuum in an evaporator may be caused by _____________.
3243 In the operation of a two-stage flash type distilling plant, the rate of scale formation is greatly reduced by _________.
A. wet steam entering the air ejector nozzle A. operating the unit at its rated capacity
B. pinhole leaks in the evaporator tube nests B. maintaining a relatively high feedwater temperature
C. rapid scaling on the evaporator tube nests C. the fact that the first-stage regulator keeps the heater shell at a constant pressure
D. high water levels in the last effect D. the fact that no boiling occurs on heat transfer surfaces anywhere in the unit
Ans: A Ans: D
3244 Which of the listed chemicals can be routinely used to maintain the hygienic quality of potable water?
3245 When any low pressure distilling plant is operated at less than the designed vacuum, the _____________.
A. Hydrochloric acid A. heat level drops
B. Chlorine B. capacity increases
C. Sulfuric acid C. scale formation increases
D. Zinc chromate D. distillate purity increases
Ans: B Ans: C
3246 Potable water piping systems installed aboard ships must be _______.
3247 Short cycling of the potable water pump is avoided by the proper use of a ________.
A. disinfected monthly with a chlorine compound A. hydro-pneumatic tank completely filled with compressed air at system operating pressure
B. independent of all other piping systems B. hydro-pneumatic tank filled with water
C. cadmium lined to prevent internal corrosion C. charge of air, at 1.4 kg/cm2 (137.9 kPa) above system pressure with the hydro-pneumatic tank one quarter full of water
D. flushed each time potable water is taken onboard D. charge of air, at system pressure, when the hydro-pneumatic tank is half full of water
Ans: B Ans: D
3248 A recirculating line is provided in the potable hot water system to __________.
3249 Which of the following components would be necessary for the proper operation of a potable hot water system?
A. maintain uniform inlet conditions for the constant speed supply pumps
A. Circulating pump
B. maintain flow rates which will eliminate fluid film formation in the piping
B. Drift pockets
C. return overflow from the pressure tanks back to the potable water tanks
C. Sterilizer
D. maintain the desired temperature range throughout the system D. Hydro-pneumatic expansion tank
Ans: D Ans: A
3250 A solenoid operated distillate bypass valve is installed in the discharge line between a distilling plant and the potable water tanks to prevent ____________.
3251 Distilled water from an evaporator may be discharged into a potable water tank _____________.
A. excessively warm distillate from entering the potable tanks A. through a detachable hose connection B. salty distillate from reaching the potable tanks B. after passing through an activated charcoal filter C. overfilling and overflowing the potable tanks C. after chemical analysis shows it is fit for consumption D. contaminated water from leaving the potable tanks D. through a solenoid operated three-way valve
Ans: B Ans: D
3252 Brine density in a distilling plant is measured with a/an _____________.
3253 Tube leaks in the distillate cooler of a two stage flash evaporator will result in _____________.
A. psychrometer A. loss of second stage vacuum
B. salinometer B. contamination of the distillate
C. anemometer C. lower feed inlet temperature
D. sphygmomanometer D. contamination of the second stage condenser
Ans: B Ans: B
3254 In a flash type evaporator, all saltwater headers are vented through individual vent cocks to the _________.
3255 Why would a flash type distilling unit be more efficient when operated in cooler seawater temperatures?
A. saltwater heater shell A. Steam carryover between stages is reduced.
B. second-stage condenser B. Evaporator vacuum is increased.
C. atmosphere C. The amount of available flash steam is decreased.
D. second-stage flash chamber D. Feedwater flow from the feedwater heater is increased.
Ans: C Ans: B
3256 The condensers located in the various stages of a flash evaporator are cooled by _____________.
3257 The steam coils in a high pressure evaporator used for saltwater service should be descaled with _____________.
A. distillate A. a wire brush
B. seawater B. a needle gun
C. brine C. a chipping hammer
D. air D. soap and water
Ans: B Ans: A
3258 Scale accumulation on evaporator heating surfaces will cause ___________.
3259 If the rated distillate production of a submerged tube type evaporator cannot be maintained with the supplied maximum steam flow rate, the evaporator ______________.
A. immediate loss of vacuum A. chemical feed must be increased
B. increased distillate quality B. has a serious brine leak
C. immediate tube failure C. temperature switch is defective
D. reduced evaporator capacity D. heating surfaces are scaled
Ans: D Ans: D
3260 The first stage feedwater temperature and shell absolute pressure in a multistage flash evaporator is _____________.
3261 In a two stage flash evaporator, operating conditions in the second stage, as compared to the first stage, are _________.
A. equal to the second stage feedwater temperature and shell absolute pressure
A. higher temperature and higher absolute pressure
B. higher than the second stage feedwater temperature and shell absolute pressure
B. higher temperature and lower absolute pressure
C. lower than the feedwater temperature and shell absolute pressure in the second stage
C. lower temperature and higher absolute pressure
D. higher than the second stage feedwater temperature but at a lower shell absolute pressure
D. lower temperature and lower absolute pressure
Ans: B Ans: D
3262 A vacuum differential is maintained in the distillate circuit between any two stages of a multiple stage distilling plant by the use of a/an ____________.
3263 The average salinity of normal seawater, when expressed as brine density is equivalent to _____________.
3264 Salinity cells are strategically installed in distillingunits to indicate the ___________. I. purity of the distillate produced II. quality of the distillate produced
3265 Potable and nonpotable water systems aboard ship _________.
A. I only A. may be temporarily connected with a removable spool
B. II only B. are permanently connected through a double stop valve
C. Both I and II C. may never be cross-connected by any means
D. Neither I nor II D. may be connected if they are used only for wash water
D. Neither I nor II D. may be connected if they are used only for wash water