-
291: The speed at which the crankshaft rotates is measured in what unit?
Revolutions Per Minutes (RPM).
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292: What is the formula used to determine indicated horsepower?
IHP=PXLXAXN/33,000 where P=means indicated pressure; L Length of stroke, in feet; A effective area of the piston, in square inches; N= Number of strokes per minutes, and 33,000= units of power (one horsepower) in foot-pound per minutes.
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293: What are two phases of a diesel run in schedule?
First Phase is running in at no load and the second phase is running in at a progressively high load.
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294: What is the maximum lube oil temperature when conducting bearing run in check?
120 Degrees F.
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295: How will the surface of an improperly seated piston ring look on a two cycle engine?
Have a dull appearance and may have black carbon build up where blow by occurred.
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296: During diesel engine run in readings are taken at what interval?
Every 15 minutes.
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297: What is the purpose of the crankcase vacuum system?
Reduce lube oil contamination caused by blow by of the combustion chamber past the piston rings into the crankcase.
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298: If you are operating a diesel engine and discover a decrease in crankcase vacuum, what should you investigate first?
Check the engine crankcase vacuum U-tube manometer for proper operation.
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299: How is the crankcase manometer total reading calculated?
By adding the two reading (both Tubes) together.
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300: What medium is used a liquid within the crankcase manometer?
Water.
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301: What causes a difference in crankcase manometer leg readings?
Incorrect Zero adjustment.
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302: Brake horsepower is defined as what?
Known as the amount of power available for useful work, the sum totals of all mechanical losses deducted from total IHP
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303: What is the most effective diesel starting fluid?
Diethyl ether.
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304: Diethyl ether must ever be used when what is installed?
Air inlet pre-heaters.
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305: What adverse effect is caused by prolong periods of idling a diesel engine at no load?
Causes heavy carbon deposits within the engine.
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306: What is the recommended load on a warm diesel engine?
60-80% of full load.
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307: What readings must be taken prior to operating a diesel engine in dry dock?
Crankcase deflection and trust readings.
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308: Diesel engine means effective pressure (MEP) is limited by what three factors?
Heat loss, volumetric efficiency, fuel air mixture.
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309: In a direct drive ship, what determines the diesel engine mean effective pressure?
The RPM of the Shaft.
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310: What is the most economical diesel engine rated speed?
90% of rated speed.
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311: Define diesel engine efficiency?
The amount of power developed as compared to the energy input which is measured by the heating value of the fuel consumed.
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312: How is diesel engine cycle efficiency determined?
By dividing the output by the input.
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313: The term compression ratio refers to what?
The ration of the volume of air above the piston, when the piston is at the bottom dead center position and the volume of air above the piston, when the piston is at top dead center position.
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314: What does mechanical efficiency equal?
BHP/HPx100
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315: What is mechanical efficiency?
The amount of power developed by the expansion of gas in the cylinder.
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316: What factor has the most effect on mechanical efficiency?
Friction within the diesel engine.
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317: Volumetric efficiency is the relationship between the quantity of intake air and what?
Piston displacement.
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318: Volumetric efficiency does not apply to what type of diesel engine?
Two stroke cycle engines.
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319: Who authorized to calibrate fuel injector systems?
Only qualified shop personnel and repair facilities.
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320: Is it allowed to adjust fuel rack setting to equalize exhaust temperatures?
No, never adjust fuel rack to compensate.
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321: What type of test should be performed after replacement of liner and before installing pistons and heads?
A pressure test.
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322: Where does a cylinder liner suffer the most wear?
At an area 90 degrees to the crankshaft and in the direction of piston thrust.
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323: What publication contains general information on all types of diesel engines?
NSTM 233.
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324: What are five symptoms of a diesel engine being unbalanced?
Black exhaust smoke, high exhaust temperature, high lube oil and cooling water temperatures, excessive heat, excessive vibration.
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325: How can you verify that black exhaust smoke is causing cylinder overload?
By opening the indicator cock on each individual cylinder and checking the color of the exhaust.
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326: How are cylinder liner stored?
Well greased and stored vertically on end only.
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327: How are unserviceable sodium filled exhaust and intake valves disposed of?
Per local regulations and instructions.
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328: What can happen to a cracked sodium filled intake valve that comes in contact with water?
A possible explosion as the sodium becomes explosive.
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329: How do exhaust pyrometers work?
The thermocouple located in a protective tube converts the heat sensed into an electrical signal that is proportional to the temperature.
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330: What would be the likely cause of a slowly responding exhaust pyrometer?
Excessive carbon buildup.
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331: What are two types of pyrometer?
Fixed and portable hand-held.
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332: On a hand-held pyrometer what is the zero adjuster set to?
Ambient room temperature vice 0 degrees F.
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333: How many foot pound equal 1 BTU?
778 foot pound.
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334: What type of engine efficiency measures completeness of combustion?
Thermal efficiency.
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335: Diesel engine piston serve what three purpose?
1. To seal the combustion and compression pressure within the cylinder. 2.Transfer heat from the piston to liner. 3. To meter the required lubricating oil to the liner and rings.
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336: What is the pressure drop across each compression ring on a properly functioning set of compression rings with open gaps?
The pressure drop in � the pressure above the ring.
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337: Too much oil distributed by the oil control ring will have what adverse effect on compression ring operation?
Ring breakage or flutter.
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338: When is single piston replacement recommended?
Only during emergencies, normally all rings on one piston will be replaced.
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339: Improper cleaning of piston ring lands and grooves will have what effect on newly installed piston rings?
Excessive wear will occur causing premature failure.
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340: What action must be taken when piston pins have surface defects?
The pins must be replaced, never use sandpaper or emery cloth to remove the defect.
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341: When taking compression readings on a 6-71 engine, what is the required engine rpm?
600 RPM.
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342: What are two types of cylinder pressure indicators?
Spring balanced and trapped pressure type
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343: What type of cylinder pressure indicator uses a spherical ball piston?
Spring balance indicator.
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344: What type of trapped pressure indicator uses a bourdon tube gage connected to a cylindrical pressure chamber?
Kiene Indicator.
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345: When obtaining data from propulsion engines for plotting on trend analysis graphs, what range should the ordered speed be maintained?
Between a standard and bull bell.
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346: At what periodicity is the first check of oil consumption recorded on a newly overhaul engine?
200 hours.
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347:What is the require PMS periodicity when conducting a diesel trend analysis on an emergency diesel generator?
Every quarter or 400+-50 hours of operation
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348: When handling a pressure indicator during compression and firing pressure testing, what is the required safety gear?
Welders gloves.
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349: What is the minimum amount of run time load required prior to data collection, when conducting an emergency diesel generator trend analysis?
2 hours at 80% load.
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350: Cylinder pressure indicators are required to be calibrated at what interval?
Every 24 Months
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351: What is used to maintain the correct freshwater temperature during engine operation?
An automatic regulating valve
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352: When should Babbitt bearings be renewed?
When the bearing is wiped, worn beyond limits, excessive honeycombed, and when sufficient bearing metal is broken loose from the shell.
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353: What causes circumferential bearing grooving and scratching?
Dirt in the lubricating oil.
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354: Bearing scraping should only be used in what applications?
To blend or smooth oil groove edges and remove high from the bearing surface.
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355: Small boat engine coupling should be visually inspected at what interval?
Daily.
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356: How is critical speed marked on the engine tachometer?
By a red mark
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357: Detailed information pertaining to diesel engine critical speed can be located in what publication?
NAVSEA Technical manual.
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358: What causes engine crankshaft torsional vibration?
Firing pulses of the cylinders
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359: Engine crankshaft torsional vibration is defined as what?
A periodic motion twisting in alternately opposite directions of the crankshaft about its longitudinal centerline.
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360: Where are the greatest crankshaft stresses created by critical vibration normally located?
In the crankpin or crankshaft cheek area,
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361: Who sets the limits on permissible stresses during critical vibration?
The engine manufacturer.
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362: What component limits instantaneous fluctuations in crankshaft speed during sudden changes of load and carries the pistons over the compression pressure?
The flywheel.
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363: What are three methods of connecting the flywheel to the crankshaft?
Split hub flywheel, tapered shaft and hub, flange connections.
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364: What is installed on some crankshaft to balance the off-center weight of the individual crank and balance the centrifugal forces created by the rotation of the crank?
Counter weights
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365: If counter weights are removed for any reason they must be marked in what manner prior to disassembly?
By match marking the shaft and the counter weight with punch marks
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366: The small clearance between the flywheel and the housing is filled with what on a viscous type vibration damper?
A viscous silicone compound
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367: What type of damper uses a spider gear with external teeth and an intermediate ring with interval teeth?
A gear type damper ( hydraulic)
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368: What provides the damper action in a gear type damper?
Strategically placed drilled vent holes
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369: What type of damper has two or more symmetrically located, heavy steel segment or balances suspended so that they can swing in the plane of rotation?
Pendulum Type.
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370: How are pendulums suspended in a pendulum type damper?
On pins inserted through holes drilled in sectors and in the housing.
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371: What dissipates the vibration energy in a harmonic balancing damper?
By the friction of the leaves of the spring�s inelastic coupling between the crankshaft and the main flywheel.
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372: When are viscous vibration dampers normally changed?
During engine overhaul if not specified IAW PMS.
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373: How often is engine alignment required to be checked?
At original installation, after overhaul, when engine blocks are lifted or separated from sub-base foundation repairs, collision, grounding and after each undocking.
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374: Regardless of machinery condition, engine alignment must not be checked for how many hours after undocking?
48 hours.
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375: What is used to correct minor deficiencies in engine alignment?
Shims.
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376: Excessive deformation of shims can cause what vibration effect?
A loss of bolt preloading.
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377: What is the only authorized shims used on diesel engines and their driven equipment?
Composition three shims, corrosion resistant steel, per MIL-S 22499 up to.050 inches thick.
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378: Shims are never used in what type of engine installation?
High chock installation.
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379: Epoxy shocks are only used in what class of ship?
MSO
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380: What tool is used to determine improper main bore misalignment on a large diesel engine?
Deflection/ strain gage.
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381: How is main bearing bore alignment checked on small diesel engine?
By removing the crankshaft and bearing inserts, then torquing the bearing caps in place, once this is accomplished a mandrel is used to check alignment.
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382: What is the first step to correct engine and coupling misalignment on a main propulsion diesel engine?
Align the coupling to the drive shaft.
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383: What tool is used to check crankshaft alignment?
Crankshaft deflection/ strain gage..
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384: Where is the crankshaft deflection strain gage placed to obtain a reading?
Placed between the crank webs
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385: When conducting crankshaft deflection checks, if the pointer of the deflection/strain gage moves toward the plus side of zero, the webs are moving in what direction?
The webs are opening.
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386: The deflection/strain gage is divided into what incrementations?
1/1000 of an inch.
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387: When using a deflection/strain gage what determines the magnitude of the indicator pointer swing?
Depends on where the gage is located on the webs
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388: What requirement must be done prior to conducting crankshaft deflection readings?
The Cylinder pressure indicator valves must be open and the engine prelubed.
-
389: What tool is recommended to apply punch marks to a crankshaft?
A needle valve from a scrapped fuel injector.
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390: Deflection/strain gage reading should be taken with the engine at what temperature?
Ambient/cold
-
391: How far is the deflection/strain gage pre-loader to prior to conducting readings?
1/3 of its travel/
-
392: When conducting deflection/strain gage readings of a crankshaft, reading shall be taken in how many position?
Five.
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393:When conducting deflection/strain gage readings on a crankshaft, what action must be taken if readings 1 and 5 vary more than � thousands?
Repeat the readings to check for consistency.
-
394: Why is position 3 most crucial when conducting deflection/strain gage readings?
Because it indicates bearing wear, condition of foundation and position of outboard bearing.
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395: What is the rule of thumb used for reading a deflection/strain gage?
.0001 inch for each inch stroke other than the last throw on the flywheel end.
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396: A crankshaft that has all +(plus) deflection readings will have what relative shape?
Webs open and the crankshaft is convex upwards.
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397: Highly stressed areas of a large diesel engine block can be inspected using what method?
Magnetic particle method.
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398: What defines a highly stressed weld area on a large diesel engine?
Welds between bearing blocks and main vertical frames, welds between decks and main frames, welds of ribs and gussets in vertical drive housing and flywheel and frames.
-
399: Magnetic particle NDT must be used on what type of engine?
Isotta Franchini.
-
400: All welds repairs conducted on diesel engines must be in accordance with what standard?
MIL-STD-278
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401: Who is the approving authority on all diesel engine weld repairs?
NAVSEA.
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