Turbines/ Reduction Gears and Propellers Flashcards
propellers are visually inspected at what periodicity?
semi-annualy
what is used to clean the prairie holes on a propeller?
low pressure air
what reference can be sued to find general information on main engine reduction gears?
NSTM 9420
what two types of reduction gear teeth are in use today on propulsion reduction gears?
herring bone and helical gears
main reduction gear pinion’s are made from what material?
forged steel
the maximum allowable bearing temperature during engine operation is?
180 degrees F
what device prevents rotation of the propeller during a casualty?
main engine locking device
what medium is used to cool the stern tube during operation?
seawater
after securing the engine, equalized cooling of the shaft is made possible by what device?
main engine jacking gear
the main engine locking device should only be engaged when?
the ship is dead in the water and the propeller is not turning
when approaching port or an anchorage, main engine lube oil temperature is reduced to what temperature?
100 degrees F
why is the main engine lube oil temperature lowered to 100 degrees F upon reaching port or an anchorage
to minimize moisture buildup and rust formation on the reduction gears
when laying up reduction gears for an extended period what is used to keep them moisture free?
dehumidifier
the main reduction gear dehumidifier system must be checked at what frequency for correct operation?
daily
permission to open any access to the main engine reduction gears must be obtained from whom?
engineering officer
backlash of main engine reduction gears refers to what?
the gear play between the surfaces of the teeth in mesh measure at the pitch circle
what increases engine backlash?
gear wear
what NSTM deals with propulsion and SSTG turbines?
NSTM 231
the high pressure turbine element is normally defined as what type of turbine?
impulse type
the low pressure turbine element is normally defined as what type of turbine?
reaction type
what connects the high pressure turbine to the low pressure turbine?
crossover or cross under pipe
why are extraction valves fitted on some LP and HP turbines?
to increase steam cycle efficiency
what does the term impulse turbine refer to?
a turbine in which the steam impinges upon the rotor blades and moves the rotor by a. direct push
what type of steam turbine moves the rotor by the force of reaction?
reaction turbine
what two main factors determine whether the rotor is moved by a direct impulse or reaction?
by the angle at which the steam hits the moving blades
on an impulse turbine were does the steam lose pressure and gain velocity?
the nozzle
in the moving blades of an impulse turbine, steam loses velocity, and pressure does what?
remains constant
what type of turbine does not have a nozzle to direct steam, but has a set of fixed blades?
reaction
what is the function of the fixed blades of a reaction turbine?
to direct the steam flow to the moving blades
what is considered a stage on an impulse turbine?
one set of nozzles and the succeeding row or rows of moving and fixed blades
what is a single stage impulse turbine usually called?
rateau
what is the definition of a Curtis stage turbine?
a velocity compounded impulse turbine
what does the term radial flow mean?
steam flows radially either toward or away from the axis of the rotor
the astern turbine elements are located in what turbine?
the low pressure turbine
what prevents foreign material from entering the high pressure turbine steam chest?
the main steam strainer
what is the purpose of gland sealing steam?
prevents steam from leaking out of the main engine and air from being introduced into the engine
turbine casing drains normally drain to what piece of equipment or system?
low pressure drain system or main condenser
the main engine thrust bearing is normally what type?
kinsgbury pivoted segmental show type
the kingsbury thrust bearing shoes serve what purpose?
the shoes are free to tilt and form the hydrodynamic wedge of oil between its babbitt face and the thrust collar
what device is installed on main engine thrust bearings to indicate flow?
bullseye bubblers or as properly termed sight flow indicators
what is the minimum allowable lube oil temperature prior to jacking the main engine over?
90 degrees F
a bowed rotor is caused by what?
improper warmup or overheating of the rotor
information on correcting a bowed rotor casualty can be found where?
engineering operation casualty control (EOCC) guide or NSTM 231
what does the term singled up refer to when dealing with propulsion turbines?
singled up is used as an emergency means of getting underway when a casualty accurst to either the HP or LP turbine in which one is placed out of commission. Singled up of a turbine required the operator to disconnect one of the turbine’s power driven unit
what does the term locked train reduction gears refer to?
the two first reduction pinions are locked between the two first reduction gears and transmit power from the turbine equally to the two gears
the main engine flexible coupling serves to protect the engine from?
longitudal and angular forces
the propeller and shaft is supported outside the hull of the ship by?
strut and strut bearing
what device is installed on the main engine to prevent the leakage of steam from the engine?
labyrinth seals
