Junior Eng part 2
Card Set Information
Junior Eng part 2
Describe the function of the photo cell detector with respect to the combustion control system.
Provides the voltage signal for sustained burner ignition.
Why do we shut the manually operated fuel valves prior to performing any work on an automatically fired auxiliary boiler?
To prevent uncontrolled fuel leaks.
What happens when a component fails in the flame safeguard control for an automatically fired auxiliary boiler?
Boiler will shut down and automatic restart will be prevented.
How does the flame scanner output at high fire compare to its output at low fire?
Output voltage is proportional to flame size.
What could happen to the feed pump suction if the feed water is to hot?
Loss of suction.
A successful prepurge is dependant upon what two components?
Damper position and airflow.
Describe what happens to the flame of an automatic boiler when the steam pressure is higher than the normal operating band.
Fuel valve will shut causing the flame to go out.
If a boiler is equipped with a low level probe sensor, what will happen if the water level drops below the level of the low level probe?
Fuel valve will shut causing the flame to go out.
Why do we maintain pH within the range specified by the manufacturer?
Reduce corrosion rates.
If fuel is shutoff doe to a flame out on an automatically controlled boiler, what does 46CFR require?
Visual and audible alarm.
Describe the fusible plug on a Scotch or auxiliary boiler.
Located at or near the center of the crown sheet.
How is the fuel atomized for use when using the steam atomizer?
Steam expansion atomizes the fuel.
List the seven systems required by 46CFR63 for large automatically controlled auxiliary boiler.
Programming control system
Operating control system
Flame safeguard control system
Limit control system
Combustion control system
Fuel supply control system
List the three steps in the procedure for replacing tubes in a water tube auxiliary boiler.
Rolled, Beaded, and Seal Welded
Why is it important for safety valves to open and close rapidly?
To prevent wire drawing.
46CFR61 requires that auxiliary boilers that have undergone major repairs be hydrostatically tested to what percentage of their operating pressure?
Why do we purge boiler furnaces prior to light the fires?
To prevent explosion upon ignition.
List the major cause of heavy soot accumulations in auxiliary boilers.
What elements is basic to all complete hydraulic systems?
Fluid storage and conditioning equipment.
What hydraulic device can easily vary speed to provide high torque?
What type of valve is used to regulate actuator speed?
With what are some hydraulic fluids formulated to make them fire-resistant?
A hydraulic fluid that has poor lubricating qualities can cause what?
What is the purpose of the filters, coolers, and heaters in a hydraulic system?
To condition the fluid
The point in the operating cycle where the moving member is at rest is called the what?
What is the result of hydraulic fluid flow and pressure?
motion and force
The number of lines and fittings in a system can be reduced by using a what?
What does a pictorial diagram show?
General position and appearance of components
What is an important characteristic of a schematic diagram?
Helps you trace fluid flow
What does a solid line on a hydraulic schematic diagram always represent?
Hollow arrows on a schematic drawing will tell you that the drawing is prepared for what system?
When a hydraulic system breaks down, the cause is usually what?
interruption of flow
Which of the six basic elements of a hydraulic system is not represented by a symbol?
The preferred method for connecting a pump shaft to the drive unit is by the use of a what?
What is extremely important when joining pump and motor shafts?
Before adjusting the pressure setting of a pump, make sure that is what?
The device that provides an easy method for making hydraulic circuit mods is called a what?
For added convenience a supply valve may be provided with what?
Disregarding mechanical damage, what is the most frequent cause of solenoid failure?
After installing J.I.C. approved valve, you should test the valve with what?
Which connector should not be used in a hydraulic system?
Too comply with J.I.C., proper flare angle for tubing should be what?
37 degrees from the centerlion
What is the advantage of tube bending?
reduced number of fittings
Which hose connection is recommended for high pressure hydraulic applications?
What three things are recommended when installing hydraulic hose?
use long links
avoid twisting hose
use large diameter hose
What kind of seal can be used to compensate for cylinder wear?
A spring loaded radial seal is used to protect what?
Variable volumes can be obtained with gear pumps by variation of what?
the pump drive speed
A radial piston pump can fail to deliver rated fluid volume because of what?
obstructed suction passages or pintle
Minor internal leakage will cause oil to accumulate in a pump casing, resulting in what?
Agitation and overheating
Close tolerance will make an axial piston pump run hot if what?
low volume pumping
Constant displacement gear pumps are controlled by what?
What can control the delivery rate of a variable stroke axial piston pump?
The tilting box position
What are the most common pumps in a hydraulic system?
Cylinder should be what when testing for for external misalignment?
What will cause the cylinder to stop if its orifice becomes blocked?
Speed control valve
If the internal drain at either end of a hydraulic two way spool directional control valve cylinder became plugged, the valve would be placed in what?
Where is the filter located at in a multi-operation hydraulic system?
Between the pump and directional control valves
How often should be fluid filter elements be cleaned of replaced?
6 months or 1000 hours
How do you vary the volume discharged by a gear pump?
varying the pump drive speed
Casing obstructions in the radial piston pump will cause what to happen?
fail to deliver rated the rated fluid volume
In general, what is the purpose of the casing drain on a hydraulic pump?
Prevent damage from agitation and overheating
What determines the cushioning effect in a hydraulic cylinder?
Describe the travel of a cylinder if the cushioning valve is not open enough.
Piston abruptly slows and continues to creep to the completion of its stroke.
What is the purpose of a hydraulic system pressure relief valve?
Establishes the maximum pressure of a hydraulic system
What is the purpose of a hydraulic accumulator?
Store fluid under pressure
What is the purpose of a hydraulic system unloading valve?
Temporarily diverts pump discharge until additional flow is required
What is the purpose of a hydraulic system counterbalance valve?
Prevent stray movement of vertical load.
What is the purpose of spring-center valves, 3-position valves, 2-position valves?
directional control valves
What controls the discharge capacity of an axial piston hydraulic pump?
Fixed by the pump housing angle
Why do we try to minimize turbulence in a hydraulic system?
To minimize energy loss
Synthetic fire resistant fluids cannot operate over a wide temperature range because of what?
Their viscosity index
Hydraulic fluid that becomes excessively high in viscosity will cause what?
How far from the bottom of a reservoir should an intake pipe be placed?
After a routine overhaul or system breakdown, what should be checked out?
If pressure to control valve inlet is higher than to be delivered to the actuator, what is wrong?
the valve is defective
When should hydraulic system cycle performance be checked?
At 2000 hours
What is compression ignition?
Heat of compression which causes fuel to ignite.
Describe the energy conversions in an internal combustion engine.
Chemical to Thermal to Mechanical
In operating diesel engine, what changes as load changes?
Combustion pressure on the power stroke.
Describe the purpose of counterweights on a crankshaft.
Uniform loading and wear of main bearing.
What causes most fuel injection nozzles to open?
Fuel oil pressure
What controls the injection pressure of a common rail fuel system?
Which type of fuel system combines the injection pump with the injection nozzle in one housing?
What type of fuel injection system uses a spring loaded differential spray needle valve and individual pump for each cylinder?
Jerk pump injection
What is the purpose of the delivery check valve used in a diesel fuel injection jerk pump?
Quick cutoff of fuel injection
Describe how wrist pin bearings perform their function.
On most medium speed engines, how are the crank pins or crank journal bearing lubricated?
Drilled passages in the crankshaft
Why are connecting rod precision bearings made slightly larger than the space they are to fill?
To cause crush to lock in place.
How does a ball bearing carry its load?
2 small points diametrically opposed from each other
What are 2 general types of sliding contact bearing?
thrust and journal
Describe the construction and function of a Quill Shaft.
Lighter weight, Hollow, and axial flexibility
How do you prevent moisture accumulation in main propulsion reduction gear?
Run till temperature drops to ambient, secure oil flow, energize dehumidifiers.
What are the benefits of double helical gears?
Eliminates side tooth gear thrust.
How and why are double helical gear teeth meshed that way?
Several teeth are meshed at the same time to provide smooth continuous power transmission.
Describe the term articulated as it pertains to reduction gears.
Gears are contained in a separate sequential gear housing.
Explain the operation of an articulated double reduction gear set for a cross compounded steam turbine.
4 pinion gears, and 3 gear trains
Why are the teeth of reduction gears normally cut in a temperature controlled room?
To prevent ambient conditions from affecting machining process.
What type of friction consumes the most power and generates the most heat?
What is an effect and a solution of an increase in speed of rotation on oil lubricated bearings?
Increased heat, a fine mist spray to reduce heat.
Internal friction of a liquid
Why are their magnets in lube oil strainers?
Check for metal to metal failure, primarily for reduction gears.
If oil is leaking out from between _____/_____ is not continously drained on a variable stroke axial pston Hydraulic pump damage can occur
Valve Plate/ Cylinder Barrel
The _____ valve is used in a diesel fuel injection jerk pump to assist in quick cutoff of fuel injection
Delivery Check Valve
Reduction gears on main propeller turbines are ______ cut to eliminate gear tooth thrust
____ gears are required in articulated double reduction gear set for a cross-compounded turbine
Cracked or broken teeth of a reduction gear is the result of severe overstress due to ____ or ______
misalignment or overload
Most shafts are subject to ____ and ____ stresses
Torsional and bending
Plain journal bearings are suited for
Heavy duty, low speed
solid bronze sleeve bearings are what type of bearings
plain journal bearings
____ bearings closures roate with the shaft
Running _____ tests do not include axial runout
principle limitation of antifriction bearings is lack of resistance to ____
In a fixed and floating 2 bearing mounting ____ is carried by the fixed bearings
A good way to prevent creeping or spinning of the inner ring
_____ is likely to be considered when choosing a mounting for a anti friction bearings
______ is not an important characteristic of a plain bearing
a small ______ indicates small teeth for a gear