3rd Grade Stationary Engineer Exam Questions and Answers: Water Tube and Fire Tube Boilers, Exams of Engineering

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3rd Grade Stationary Engineer 21 – 40

Exam Questions and Answers

What is a water tube boiler? list 5 advantages list 5 disadvantages name 4 types in a water tube boiler, products of combustion pass around tubes containing boiler water ADVANTAGES:

1. rapid steamers
2. use less water
3. less chance of explosion
4. no flat surfaces
5. smaller tube sizes DISADVANTAGES:
6. elaborate settings
7. field assembled
8. initial cost per pound of steam is higher
9. greater number of openings thus more air infiltration
10. require more floor space TYPES:
11. B.&W.
12. Stirling
13. Heine
14. "D" type what is a fire tube boiler? list 5 advantages list 5 disadvantages name 4 types in a fire tube boiler, products of combustion pass through tubes or flues surrounded by water. ADVANTAGES:

1. very little setting required
2. factory assembled for fast installation
3. low initial cost
4. can be made portable
5. compact

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DISADVANTAGES:

1. slow steamers
2. limited in pressure and capacity
3. liable to disastrous explosions because drums and joints are set over the fire
4. inefficient
5. inaccessible for inspection

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TYPES:

1. H.R.T.
2. locomotive
3. Scotch Marine
4. Vertical fire tube What type stays are used in wet back (Scotch Marine) type boilers? stay bolts and through stays. these sometimes will have a telltale drilled in them describe a sectional boiler the sectional headers are built up of vertical sections or units. a sufficient number of sections are clamped together to form the desired boiler size. these boilers can be erected in an existing building by carrying them in piece by piece what is a superheater? what are the advantages of a superheater? a super heater is a device used to raise the temperature of steam without raising its pressure.
5. increases efficiency of the boiler
6. delivers dryer steam
7. dryer steam can be transmitted long distances with minimal heat loss
8. dryer steam reduces condensation and erosion what is a radiant type superheater? what is a convection type superheater? what is the third type of superheater? A radiant superheater is set over the fire to absorb radiant heat from the furnace by direct radiation a convection superheater is placed in the gas passage of the furnace, usually between the first and

second pass. little to no radiation will reach this type the third type is a combination of radiant and convection what is an economizer? what is an air pre-heater? an economizer is a heat exchanger designed to recover waste heat from the products of combustion by pre-heating the feedwater. It's located in the breaching between the boiler and stack. NOTE: there is great economy in heating feedwater. the air pre-heater consists of a series of tubes or plates that have hot gasses on one side and incoming air on the other. heat in the hot gasses leaving the boiler is recovering by the incoming air. (both reduce stack temperatures and increase boiler efficiency) what is a water wall? a set of tubes containing boiler water set in the refractory. they absorb heat that would otherwise be lost to the refractory and they increase the capacity of the boiler what is A.S.M.E. and its purpose? what code of information is stamped on the boiler? what is an A.S.M.E. symbol stamp? where are the code markings found on a boiler? American Society of Mechanical Engineers has written a set of minimum standards for the safe construction of pressure vessels.

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stamped on the boiler shell or a plate attached to the shell will be:

1. model and serial numbers
2. safe working pressure
3. date of manufacture
4. horsepower rating
5. square feet of heating surface
6. steam generation in pounds per hour
7. fuel designed for
8. ASME stamp

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the ASME symbol stamp will identify the boiler or accessory type.

fire tube boiler - it may be located by the water column near the front right side water tube boiler - it will be located next to the manhole on the steam drum what is the cross section of a 1" bolt?

DxDx.7854(1/4pi) 1x1x.7854=.7854 sq.in. show your work and label everything! what is an alloy? name 5 a mixture of two or more metals.

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1. brass
2. bronze
3. steel
4. stainless steel
5. cast iron at what pressure is the use of cast iron fittings permitted? 15 psi. or 250*F. Not to exceed either one what is meant by "Factor of Safety"? the bursting pressure divided by the working pressure or the comparison of the tensile strength to the actual working stress what is the Factor of Safety for Boilers, Flywheels and Pipe? New boilers is 4 Pre-owned boilers constructed to ASME code is 5 Flywheels is 4 Pipe is 8

1. what is a lap joint? what is a butt joint? what is a butt-strap joint? LAP JOINT = when one plate overlaps the other and is joined BUTT JOINT = when two ends of the plate meet end to end and are joined BUTT-STRAP JOINT = when two ends of the plate meet end to end and are joined by a plate. (one plate is a single butt strap joint / two plates are a double butt strap joint) is the longitudinal joint the strongest part of the boiler NO! it is the strongest type joint, but any joint is the weakest part of a boiler two boilers are make of the same grade of steel, same thickness of plate and same type of joints. one is 30" in diameter the other is 60" diameter. which will withstand the greatest pressure and demonstrate your answer

the 30" boiler-it has less total pressure on the shell. DxDx.7854(1/4pi)xpsi 30x30x.7854x120 psi = 84,823 lbs. total pressure 60x60x.7854x120 psi = 339,292 lbs. total pressure show your work on everything! what are tube ligaments? the area between the tube holes on the tube sheet what type stays are used in the heads of water tube boilers? why? there are no stays

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the head of the boiler drum is shaped with a die, which dishes and forms them in to the shape they would take as a result of the pressure to which they will be subjected why is a row of tubes sometimes left out of an HRT boiler? to improve circulation reducing carryover