What are the causes of failure of bearings?

1 Answer

Answer :

a) Faulty mounting

b) Faulty lubrication

c) Foreign matter in lubrication

d) Water in the bearing arrangement

e) Vibration

f) Inoccurrences of form of shaft or housing seating.

g) Passage of electric current.

h) Metal fatigue

Related questions

Description : The failure of ball bearings used in electric motors can result from _____________. A. failure to clean the bearing before repacking B. failure to maintain proper alignment C. excess lubrication forcing the bearing full of grease and eliminating all areas of expansion D. all of the above

Last Answer : Answer: D

Description : What are the causes of motor failure? 

Last Answer : a. Corrosion or rust. b. Excessive moisture (winding IR low and bearing lubrication loss). c. High ambient temperature. d. Poor ventilation. e. Inadequate lubrication. f. ... Manufacture defect or wrong design. m. Deterioration with age. n. Maintenance improper. 

Description : On large generators, space heaters are used to ____________. A. keep the machine at ambient tmperature of the machinery space B. maintain rotor and stator winding temperatures above the dew point ... C. prevent condensation in the lube oil D. prevent electrolysis due to condensation in the bearings

Last Answer : Answer: B

Description : To protect the rotor of a motor disassembled for maintenance or overhaul, it should be ___________________. A. suspended by wire slings in one corner of the shop B. stowed upright on its shaft C. supported by two 'V' notched wood blocks D. returned to the frame as soon as the bearings are removed

Last Answer : Answer: C

Description : On electrical generators one of the bearings is isolated from the bedplate. This insulating block should not be painted and must be kept clean to ___________. A. protect operating personnel from shock ... the prime mover as it warms up D. eliminate shaft currents to prevent damaging the bearings

Last Answer : Answer: D

Description : If the bearings of an electrical generator are failing more frequently than expected and the lubricating oil is sludging then you should ______________. A. check the connections to the output leads B. ... replace the bearing with a sealed roller type D. replace the thrust bearing of the prime mover

Last Answer : Answer: B

Description : The following air gap readings were obtained from a horizontally mounted, bilge pump, induction motor, equipped with sleeve bearings: FWD END-AFT END, Top .045 - .049, Right Side .045 - .047, Left ... the aft bearing. C. The forward bearing should be lowered. D. The aft bearing should be lowered.

Last Answer : Answer: A

Description : Air gap readings should be taken on electrical generation machinery periodicly to _________. I. determine the need for cleaning II. check the condition of the bearings A. I only B. II only C. both I and II D. neither I or II

Last Answer : Answer: B

Description : Air gap readings for electrical generating equipment should be taken periodicly. This is to _______. I. determine the condition of the bearings II. prevent damage to the rotor and stator A. I only B. II only C. both I and II D. neither I or II

Last Answer : Answer: C

Description : If air gap readings for an electical generating machine have changed significantly from the last reading, you should check _________. A. the bearings B. insulation readings and machine cleanliness C. the prime mover thrust bearing D. the field coil bolts for the proper torque values

Last Answer : Answer: A

Description : Air gap readings should be taken periodicly on electrical generation equipment to __________. A. determine the amount of varnish that can be applied to correct insulation problems B. determine the ... field coil bolts and correct lateral adjustment of the field coils D. increase machine efficiency

Last Answer : Answer: B

Description : To protect the rotor of a motor disassembled for maintenance or overhaul, it should be ___________________. A. suspended by wire slings in one corner of the shop B. wrapped in several layers of heavy ... flat wood blocks on the workbench D. returned to the frame as soon as the bearings are removed

Last Answer : Answer: B

Description : A split-phase induction squirrel-cage motor will not come up to speed, even though the rated voltage, rated frequency, and rated load are applied. The suspected trouble could be due to _____________. A. a faulty centrifugal switch B. broken rotor bars C. worn bearings D. all of the above

Last Answer : Answer: D

Description : When disassembling electric motors for maintenance or overhaul, ________________. A. punch mark frame and end bells for proper assembly B. wrap bearings in lint free cloths if they are to be reused C. tag and store small parts in a box D. all of the above

Last Answer : Answer: D

Description : The reactive power drawn by a motor from an AC generator is the power which is _____________. A. used to establish the magnetic field of the motor B. lost in overcoming friction in the ... by current flow through the windings D. transmitted directly through the rotor shaft to perform useful work

Last Answer : Answer: A

Description : One of the generator or motor bearings is generally insulated from the end housing in order to prevent ________. A. rapid brush wear B. current leakage from the shaft C. excessive field winding heat D. circulation of shaft currents induced in the machine's frame

Last Answer : Answer: D

Description : The following air gap readings were obtained from a horizontally mounted, bilge pump, induction motor, equipped with sleeve bearings: FWD END -AFT END, Top .045 - .049 , Right Side .045 - .047, Left ... the aft bearing. C. The forward bearing should be lowered. D. The aft bearing should be lowered.

Last Answer : Answer: A

Description : In the illustrated motor, roller bearings are used because __________. EL-0001 A. of their ability to absorb moderate thrust loads B. they electrically insulate the rotor from the frame reducing ... clearance between the rotor and stator is generally as close as mechanical tolerance will permit

Last Answer : Answer: D

Description : The air gap in an induction motor should be periodically checked with a feeler gage to prevent possible ___________. A. rotor contact with the stator B. axial misalignment of the rotor C. damage to the motor bearings D. electrical damage to the bearings

Last Answer : Answer: A

Description : When removing ball or roller bearings from the shaft of a motor, you should use a _____________. A. rawhide hammer B. brass mallet C. wheel puller D. soft iron pry bar

Last Answer : Answer: C

Description : The only point in the steering stand shown in the illustration which needs periodic lubrication is the ______________. EL-0098 A. repeater assembly ball bearings B. steering wheel bearing C. operation selector switch D. course selector pointer

Last Answer : Answer: B

Description : Before reassembling any machinery, you should _____________. A. replace all bearings regardless of length of service B. apply a heavy coat of oil to all mating surfaces C. clean any corroded surfaces and file all burrs smooth D. coat all parts with alemite grease

Last Answer : Answer: C

Description : Which bearings preferred for all large power motor?  

Last Answer : Plain bearings  

Description : Why do we grease the bearings?

Last Answer : a) Grease lubricant gives good protection against ingress of moisture and dirt into motor. b) Easy to seal against leakage of grease into motor compared to oil. c) Low friction torque at starting. 

Description : Where preloaded ball bearings used? 

Last Answer : If more vibration exists even when machine is not in running conditions.  

Description : What is the operating life of bearings? 

Last Answer : a) Continuous 24 hrs operation – 40000 to 50000 hrs. b) Affected by load axially or radial. c) Operating temperature. 

Description : What are the types of bearings are adopted for small motors and large motors?

Last Answer : Small motors (LT motors) Horizontal mounted - deep groove ball bearing at both ends. Medium motors Roller bearing at DE and deep groove bearing at NDE. Large motors (HT motors above 750 kW) Horizontal ... mounted - face to face angular contact ball bearing at NDE and roller or ball bearing at DE.

Description : Where automatic restart does not present a hazard after a power failure, Coast Guard Regulations (46 CFR) require motor controllers for auxiliaries vital to the propelling equipment to be provided ... overload protection B. low voltage protection C. low voltage release D. reverse current protection

Last Answer : Answer: C

Description : Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus

Last Answer : Answer: B

Description : Voltage failure of an AC generator may be caused by ____________. A. failure of the exciter generator B. a tripped bus circuit breaker C. high mica segments on the stator bus bar D. excessive prime mover speed

Last Answer : Answer: A

Description : If an AC generator experiences voltage failure, the cause may be _____________. A. an open in the field circuit B. the brushes shifting out of the neutral plane C. excessive locked-rotor current D. a rotating slip ring

Last Answer : Answer: A

Description : An alternator will fail to produce line voltage as a result of _____________. A. a closed circuit breaker B. oxidized slip rings C. improperly staggered brushes D. exciter generator failure

Last Answer : Answer: D

Description : Unnecessary and frequent applications of varnish to the generator windings to repair defective insulation will result in ____________. A. heavy coatings of varnish interfering with heat dissipation B. ... of the rectifier assembly D. a built-up of varnish without changing generator operation

Last Answer : Answer: A

Description : In the event of a power failure during cargo loading operations, the movement of an electric powered cargo winch will be stopped by ____________. A. a manual override switch B. the weight of the load on the boom C. a spring set brake D. a hand operated band brake

Last Answer : Answer: C

Description : Which of the following conditions can lead to the failure of a resistor? A. Excessive vibration B. Insufficient ventilation C. Corrosion D. All of the above

Last Answer : Answer: D

Description : When insulation failure produces a low resistance current path between two conductors, the resulting condition is known as ____________. A. an open B. a short circuit C. a ground D. a surge

Last Answer : Answer: B

Description : The 24 volt DC bus on the emergency switchboard is used to supply power to the _____________. A. general alarm system B. gyrocompass power failure alarm system C. smoke detection system D. all of the above

Last Answer : Answer: D

Description : Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. main bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus

Last Answer : Answer: B

Description : When power is restored after a complete power failure, a steering gear pump motor will ____________. A. have to be restarted B. have to be reset C. restart automatically D. trip its overload relays

Last Answer : Answer: C

Description : Humming or buzzing of electric contacts is a symptom of ____________. A. low voltage on the operating coil B. power failure to the operating coil C. a control circuit ground D. a control circuit overload

Last Answer : Answer: A

Description : If both the 'high level' and 'low level' alarms come on for the same address of a centralized control console, the most likely problem is a/an ____________. A. sensor failure B. failed alarm C. low level D. extremely high level

Last Answer : Answer: A

Description : The type of control circuit that will not permit automatic restarting after power is restored, following a power failure is called _____________. A. low voltage protection B. low voltage release C. overload lockout D. reduced voltage restart

Last Answer : Answer: A

Description : The type of feature afforded auxiliaries vital to the operation of propelling equipment, where automatic restart after a voltage failure would not create a hazard, is termed _____________. A. low voltage protection B. high amperage protection C. low voltage release D. high amperage release

Last Answer : Answer: C

Description : Grounds occurring in electrical machinery as a result of insulation failure may result from _____________. A. deterioration through extended use B. excessive heat C. extended periods of vibration D. all of the above

Last Answer : Answer: D

Description : What can be the reasons for the failure of the transformer?

Last Answer : Answer: Transformer is one of the most expensive equipments in the Power System. Failure of the transformer can cause outage of power supply for even days. However, multiple things can go wrong with ... relays. 3.Short Circuits 4.Open Circuits 5.Earth Faults 6.Over Voltage 7.Reduced system frequency

Description : What FCN was implemented to avoid reactor trip on 220V-DC failure of PHT and PPP breakers?

Last Answer : The breaker close position supervision relay VAA 21 is changed by VAJC type, contacts position do not change if 220V-DC is lost now.

Description : Why AVR changes over to manual on AVR PT fuse failure? 

Last Answer : Because loss of feedback to voltage corrector.  

Description : What is the cooling water used in moderator heat exchanger during normal operation? And during class IV failure?

Last Answer : During normal operation process LP water is used in moderator heat exchangers, which transfers heat to seawater. During class IV failure firewater is used for the moderator heat exchanger. 

Description : What causes RAM failure in the laptop?

Last Answer : There could be many different causes, including an awful power supply, unnecessary hotness, a PC infection/malware, an undermined working framework establishment or another flawed equipment component.