3. MATERIALES Y MÉTODOS
3.5. Concentración de microplásticos en las cremas
1464 The burner assembly on an automatically fired auxiliary boiler fitted with variable capacity, pressure atomizing burners, maintains steam pressure by ______________.
1465 If the combustion control system of an automatically fired auxiliary boiler fails to sustain burner ignition after a normal shutdown, you should check for a/an __________.
A. cycling on and off A. faulty photocell detector
B. changing fuel oil return pressure B. low steam pressure
C. changing the speed of a rotary cup C. high voltage on the ignition electrode
D. varying air pressure supplied to the nozzle D. open air damper
Ans: B Ans: A
1466 A three-way thermostatic control valve regulates the diesel engine cooling water temperature by passing a portion of the water _____________.
1467 The primary function of a flame safeguard system, as used on an automatically fired auxiliary boiler, is to prevent ____________.
A. around the engine A. accidental dry firing and overpressure
B. around the cooler B. uncontrolled fires in the furnace
C. to the expansion tank C. explosions in the boiler furnace
D. overboard D. overheating of the pressure parts
Ans: B Ans: C
1468 All automatically fired low pressure heating boilers must have an automatic ____________.
1469 The fuel supply system to an automatic auxiliary boiler, will be automatically shutdown if the boiler ______________.
A. fuel cutoff as a result of low water A. salinity is abnormally high
B. pressure-control regulator B. steam demand is too high
C. feedwater control valve C. water level is abnormally low
D. superheat control system D. feedwater flow is low
Ans: A Ans: C
1470 Automatic burner shutdown in an auxiliary boiler, as a result of a component failure in the flame safeguard controls, will _______________.
1471 In a diesel engine closed freshwater cooling system, the amount of coolant flowing through the heat exchanger is controlled by the _____________.
A. prevent the boiler from automatically relighting A. suction pressure regulator
B. eliminate the need for furnace purging B. thermostatic bypass valve
C. cause automatic restart after a purge period C. sea water temperature D. cause an explosion in the boiler furnace D. water level in the expansion tank
Ans: A Ans: B
1472 Under which of the following conditions must the combustion control system for a small automatic auxiliary boiler secure the burner?
1473 Temperature control valves installed in the jacket cooling water system of a diesel engine, modulates the rate of water flow through the __________.
A. High water level A. cooling water pump
B. Low steam pressure B. nozzle cooling passages
C. Flame failure C. cylinder jackets
D. High fuel oil temperature D. heat exchanger
Ans: C Ans: D
1474 At the beginning of the prepurge period on an automatic auxiliary boiler equipped with a programmed control system, the unit will not restart if airflow is not sensed and ______________.
1475 After a normal, or safety shutdown, automatic combustion control systems for an auxiliary boiler are designed to prevent the immediate refiring of a burner in order for the ________________.
A. the damper is not sufficiently opened A. furnace to be repurged
B. the damper is not fully closed B. electric charge to buildup in the igniter
C. oil pressure is not sensed C. fuel pump to restart
D. water pressure is not sensed D. drum level to stabilize
Ans: A Ans: A
1476 Which of the following types of feedwater regulators is commonly used with a water-tube, natural circulation, auxiliary boiler?
1477 Automatic combustion control systems for auxiliary boilers are designed to cycle burners on and off in response to the _______________.
A. Thermomechanical A. excess air pressure
B. Bimetallic element B. steam moisture content
C. Ring thermostat C. furnace temperature
D. Modulating pressostat D. steam pressure
Ans: A Ans: D
1478 If the operating element of a thermostatic valve installed in a diesel engine cooling system malfunctions, it may result in
______________.
1479 Automatic combustion control systems for some auxiliary boilers are designed to cycle burners on and off in response to ____________.
A. a low level in the engine expansion tank A. fuel supply pressure
B. excessively high coolant pressure B. fuel return pressure
C. improper temperatures C. steam pressure
D. malfunctioning of the jacket water heater D. furnace air pressure
Ans: C Ans: C
1480 Engine protection by means of an alarm or shutdown control can be obtained with devices that are sensitive to _____________.
1481 Control of the main propulsion diesel engines can be shifted from the engine room to the wheelhouse from the ___________.
A. temperature A. wheelhouse control station
B. pressure B. engine room control station
C. engine speed C. captain's office
D. all of the above D. chief engineer's office
Ans: D Ans: B
1482 To test the operation of the flame failure switch of an operating automatically fired auxiliary boiler, you should _____________.
1483 Electrically operated safety devices on auxiliary diesel engines function to stop the engine by _____________.
A. de-energize the high voltage ignition system A. increasing the volume of intake air
B. move the igniter away from the normal firing position B. shutting off the fuel supply C. close the manual fuel valve with the burner firing C. increasing the engine back pressure
D. shift the controls to low fire D. overspeeding the engine
Ans: C Ans: B
1484 The programmed control system of an automatic auxiliary boiler will terminate the light off process during the prepurge period if air flow is not sensed and _________.
1485 On auxiliary boilers using individual flame scanners to monitor the main and pilot flames, the main flame scanner should be sighted to ______________.
A. the damper is not sufficiently open A. detect pilot flames that are incorrectly positioned B. the damper is not fully closed B. view the refractory directly opposite the main burner
C. oil pressure is not sensed C. avoid detecting the pilot flame
D. water pressure is not sensed D. view the main flame in its outer periphery
Ans: A Ans: C
1486 Automatic combustion control systems for some auxiliary boilers are designed to cycle burners on in response to ____________.
1487 If the flame of an automatically fired auxiliary boiler tends to move away from the burner tip when the firing rate is changed from low to high, you should ____________.
A. low fuel pressure A. decrease the fuel pressure
B. fuel return pressure B. adjust damper linkage to slow the opening rate of the dampers
C. low steam pressure C. adjust damper linkage to lengthen the purge period
D. furnace air pressure D. adjust the photocell to observe the new flame position
Ans: C Ans: B
1488 Which of the following conditions will cause only one of the burner solenoid valves to close on an automatically fired, two burner unit, auxiliary boiler?
1489 While an auxiliary boiler is operating at design load, which of the following actions will occur if the automatic combustion control system detects a steam pressure drop?
A. Loss of the forced draft fan A. More burners will be lighted off.
B. Low boiler water level B. The registers will open fully.
C. High boiler water level C. The fuel oil valve and air damper will open wider.
D. A faulty coil in one the solenoid valves D. The steam flow will be automatically regulated
Ans: D Ans: C
1490 The main propulsion diesel engine jacket water temperature rises above normal, with the raw water sea suction and the expansion tank water level being normal. Which of the following problems is most likely the cause?
1491 Constant capacity pressure atomizing fuel oil burners installed on automatically fired auxiliary boilers, respond to variations in load demand by ____________.
A. Faulty thermostatic bypass valve. A. automatically increasing the fuel/air ratio B. Eroded zinc pencils in the heat exchanger. B. automatically cycling the burner on and off
C. Steam formation in the expansion tank. C. responding to the boiler high and low water level limit switches
D. Excessive leakage from jacket water pump seals. D. regulating the fuel oil service pump discharge pressure
Ans: A Ans: B
1492 Burner ignition failure in an automatically fired auxiliary boiler would be caused by ____________.
1493 An automatically fired auxiliary boiler is required by Regulations to be shutdown as a result of ____________.
A. a burned out solenoid in the oil supply valve A. low boiler pressure
B. high temperature excess air B. low water level
C. incorrectly setting the hotwell dump valve C. wide flame cone angle D. an incorrectly positioned burner snubber assembly D. high fuel oil pressure
Ans: A Ans: B
1494 If the combustion control system of an automatically fired auxiliary boiler fails to restart from the normal shutdown mode, you should check for ______________.
1495 When the steam pressure drops below a set value on an automatically fired auxiliary boiler, fitted with rotary cup atomizers, the combustion control system will _________.
A. broken or grounded high tension leads A. increase the fuel oil control valve opening
B. a faulty ignition cable connector B. increase the rotary cup speed
C. an incorrect electrode setting C. decrease the back pressure regulating valve opening
D. all of the above D. decrease the supply steam control valve opening
Ans: D Ans: A
1496 The jacket water temperature in a diesel engine closed freshwater cooling system is normally controlled by _____________.
1497 On an automatically fired auxiliary boiler, the steam pressure limit switch is wired into the burner electric circuit to ______________.
A. regulating the level of corrosion inhibitor in the primary cooling system
A. energized the flame scannercircuit when high boiler pressure is reached
B. the level of the freshwater expansion tank B. sound an alarm when the burner is shut off
C. varying the engine load to meet temperature requirements C. shut off the burner when the cutoff pressure is reached D. the operation of thermostatic valve D. maintain smokeless fuel oil atomization
Ans: D Ans: C
1498 A failure of any component of a flame safeguard control for an auxiliary boiler will result in ____________.
1499 The fuel oil supply system to an automatic auxiliary boiler, will automatically shutdown if the boiler _____________.
A. a furnace explosion A. steam demand is high
B. automatic burner shutdown B. salinity is high
C. uncontrolled firing C. safety valve simmers
D. automatic restart D. burner flame is extinguished
Ans: B Ans: D
1500 Control of the fuel oil metering valve in an automatically fired auxiliary boiler is accomplished by a ___________.
1501 The pressostat is installed on an auxiliary boiler to sense steam pressure changes, it _______________.
A. pressure magnifying device in the steam coil outlet A. controls the flow of feedwater to the boiler
B. signal from feed water electrode B. monitors the boiler high water level
C. metering device in the air supply line C. secures the fires when a fusible plug burns out
D. steam pressure sensing device with linkage to the damper air vanes
D. automatically regulates the quantity of oil and air flow to the burner
Ans: D Ans: D
1502 Which of the automatic boiler controls listed should be tested prior to lighting off an auxiliary boiler?
1503 A photoelectric cell installed in an automatically fired auxiliary boiler burner management system ________________.
A. Automatic bottom blow valve A. opens the burner circuit upon sensing a flame failure
B. Low water level cutoff switch B. must be bypassed at low firing rates
C. Voltage output of the ignition transformer C. requires mechanical linkage to secure the burner fuel supply D. Insulation resistance readings in the ignition system high tension
leads
D. detects a flame failure by monitoring radiant heat from glowing refractory
Ans: B Ans: A
1504 If the jacket water temperature in an auxiliary diesel engine cooling system is lower than normal, the probable cause is _________.
1505 Diesel engine control can be obtained by the bridge _____________.
A. air binding of the engine cooling system A. at any time
B. a cracked water cooled exhaust manifold B. only after the engine room control station is switched to "bridge control"
C. blockage in the heat exchanger C. whenever the secondary station is switched to "bridge control"
D. faulty operation of the thermostat D. with the approval of the chief engineer only
Ans: D Ans: B
1506 The temperature at which an adjustable bellows type thermostat valve is set by ______.
1507
A. changing the position of the actuating bulb B. replacing the bellows with a heavier spring C. varying air loading pressure to the bellows D. changing spring compression to oppose bellows Ans: D
1508 Where diesel engine speed and clutch controls are combined into one operation by a single control lever, movement of the lever from the "stop" position to the "ahead" position will FIRST
____________.
1509 The control system for a controllable pitch propeller can be programmed ___________.I. to produce a maximum combined propeller and engine efficiency between pitch and a given engine speed II. for continuous operation of the engine at pre-setconditions
A. decrease the engine speed A. I only is correct
B. increase the engine speed B. II only is correct
C. engage the ahead clutch C. both I and II are correct
D. disengage the astern clutch D. neither I or II are correct
Ans: C Ans: C
1510 A diesel engine is operating at 1800 RPM and driving a propeller at 600 RPM. What is the speed reduction ratio?
1511 The torque transmitted by an electromagnetic slip coupling is dependent upon excitation and the _____________.
A. 0.30 to 1 A. engine speed
B. 3.00 to 1 B. harmonic frequency
C. 3.33 to 1 C. amount of slip
D. 33.0 to 1 D. resonance
Ans: B Ans: C
1512 Which of the couplings listed will prevent shock loads from being transmitted to an engine?
1513 In most marine single reduction gear units, the spur gear is driven by the _____________.
A. Grid A. quill shaft
B. Dog type B. helical gear
C. Friction C. pinion gear
D. Hydraulic D. spur gear
Ans: D Ans: C
1514 Hydraulic couplings will transmit torque equal to the input torque by means of energy changes in a rotating vortex of liquid. For the vortices to form, there must be __________.
1515 Helical reduction gears, as used with main propulsion drive trains, are constructed so that several teeth are meshed at the same time to ____________.
A. slip between the impeller and runner A. eliminate propeller shaft end thrust B. less than 2 per cent slip between the impeller and runner B. translate heavy load into high speed output C. axial thrust generated by the runner pinion shaft C. provide smooth continuous power transmission D. momentary torsional vibration transmitted by the driving impeller D. allow construction with fewer gear teeth
Ans: A Ans: C
1516 Which of the following characteristics is true relative to meshing spur gears?
1517 Gear-type flexible couplings are often used in diesel engine drive trains because they _____________.
A. The gear of larger diameter will rotate at a slower RPM. A. require no lubrication under normal operating conditions B. Both gears will operate in the same direction. B. compensate for gross misalignment in the drive train C. The teeth on the larger gear are larger than the teeth on the smaller
gear.
C. are able to transmit high torque, even where slight misalignment exists
D. Power can be transmitted at a 90° angle. D. will rapidly disconnect the engine from the line shaft
Ans: A Ans: C
1518 When used with reversing reduction gears, medium-speed diesel engines should be bolted to their foundations with fitted bolts at the drive end and clearance (loosely fitted) bolts in other locations. This is done to _____________.
1519 The best method for determining the amount of eccentricity or offset misalignment between the disconnected propeller shaft coupling flange and the reduction gear output flange is by using a _____________.
A. maintain alignment when the ship's hull is working in heavy seas A. straight edge laid across the flange edges POWER TRANSMISSION,GEARS AND CLUTCHES
B. ensure engine vibrations correspond to the natural frequency of the hull
B. thickness gauge between the separated flange faces
C. permit the engine to expand away from the driven equipment as the engine heats up and expands
C. bridge gauge to check the position of each flange in relation to the other
D. maintain engine thrust bearing clearances D. dial indicator mounted on one flange indicating any misalignment of the other flange
Ans: C Ans: D
1520 A flexible coupling is located between the _____________. 1521 Reduction gear casings are vented in order to _____________.
A. engine and the pinion A. allow windage to exist for cooling the gears
B. line shaft and tailshaft B. avoid a buildup of pressure within the gear case
C. pinion and the bull gear C. avoid lube oil foaming within the case
D. thrust bearing and the worm gear D. allow for proper lubrication of the friction clutch shoes
Ans: A Ans: B
1522 Which of the types of reduction gearing listed is best suited for medium speed main propulsion units?
1523 Misalignment of the drive shaft and propeller shaft flanges can be detected by using a dial indicator or _____________.
A. Hypoid A. inside micrometer
B. Helical B. feeler gauge and straight edge
C. Cyclical C. adjustable trammel
D. Spur D. sighting device
Ans: B Ans: B
1524 Which of the bearing types listed is most commonly used in smaller vessel main propulsion reduction gears as thrust bearings?
1525 When more than one propulsion diesel engine is connected to a single propeller shaft through reduction gears, the gears are usually _____________.
A. Ball bearings A. single reduction
B. Poured bearings B. double reduction
C. Sleeved bearings C. triple reduction
D. Tapered roller bearings D. quadruple reduction
Ans: D Ans: A
1526 Which of the following statements is correct concerning a hydraulic coupling?
1527 One advantage of hydraulic clutches over mechanical clutches in diesel engine installations is ____________.
A. Rapid declutching is impossible. A. the power is transmitted at a very high efficiency of 60%
B. Accurate alignment between the rotating members is extremely important.
B. the torsional vibrations are transmitted directly to the reduction gears
C. Torque is controlled by the volume of oil in the coupling. C. each clutch has a separate oil gland for reverse operation D. Torsional vibrations from the engine are transmitted directly to the
hull by the coupling.
D. no mechanical connection exists between the driving and driven elements
Ans: C Ans: D
1528 The magnetic lock between the armature and field in an electromagnetic coupling is established by _____________.
1529 In reducing engine speed to an efficient propeller speed by the use of reduction gears, ____________.
A. controlled engine speed A. speed and torque are both reduced
B. energizing the field coils B. speed is reduced and torque remains unchanged
C. brush contact with the armature C. speed is reduced and torque is increased
D. rotating the primary rotor D. speed is sometimes unchanged while torque is increased
Ans: B Ans: C
1530 When changing the direction of propeller shaft rotation in a diesel plant equipped with a pneumatic clutch, you must pause at neutral to allow the _____________.
1531 Airflex clutches are used to transmit power from a diesel engine to the propeller shaft. A restricted orifice is used in the control air system of this unit to _____________.
A. fuel rack to readjust A. delay deflation of the clutch being disengaged
B. engine to slow down B. delay inflation of the clutch being engaged
C. propeller to stop C. reduce the deflation time of both clutches
D. clutch to deflate D. reduce the inflation time of both clutches
Ans: D Ans: B
1532 The power loss associated with slip in a fluid coupling appears as __________.
1533 Slippage of an air operated friction clutch can result from _____________.
A. chattering in the driving member A. an overloaded engine
B. heat in the hydraulic fluid B. prolonged slow speed operation
C. vibration in the driving member C. weak disc springs
D. leakage around the ring valve D. newly installed friction blocks
Ans: B Ans: A
1534 Pitting in the area close to the pitch line and on the same end of each gear tooth of a reduction gear unit would be caused by _____________.
1535 When an additional load is applied to a diesel engine which is using an inadequately inflated air bladder clutch unit, you can expect _____________.
A. corrosion on the gears A. pneumatic seizure
B. excessive gear speed B. overheating because of slipping shoes
C. dirt in the oil C. chipped reduction gear teeth
D. misalignment of the gears D. excessive wear on the thrust bearings
Ans: D Ans: B
1536 Pitted reduction gear teeth having a deep blue color with evidence of overheating have been operated with __________.
1537 Misalignment of the drive shaft and propeller shaft flanges can be detected by using a dial indicator or _____________.
A. excessive speed A. inside micrometer
B. improper warm-up B. feeler gauge
C. extreme misalignment C. adjustable trammel
D. inadequate lubrication D. sighting device
Ans: D Ans: B
1538 A gear type flexible coupling is precision built for _____________. 1539 Effective hydraulic coupling operation depends upon a certain amount of _____________.
A. reduced torsional vibration and resonance A. slip
B. increased slip and maneuvering capability B. mechanical friction C. high torque transmittal under limited misalignment conditions C. fluid overheating D. low axial thrust transmission under minimal alignment irregularities D. torsional vibration
B. increased slip and maneuvering capability B. mechanical friction C. high torque transmittal under limited misalignment conditions C. fluid overheating D. low axial thrust transmission under minimal alignment irregularities D. torsional vibration