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City of Omaha 3rd Grade
N.A.P.E. Stationary Engineers
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How can you lose your license? - answer Drinking on the job / sleeping on the job / negligence / unsafe work / failing to renew your license annually / signing a falsified licensing application for someone What must you do if you change jobs? - answer You must notify city hall if you change jobs, change your address or if you retire Why should you do rounds? - answer You do rounds so that you can find and correct problems to prevent break downs. Keeping permanent records will make it easier to forecast most breakdowns because you will get to know your equipment. What is a steam Boiler? - answer A steam boiler is a closed vessel PARTIALLY FILLED with water, under pressure, that transforms water into steam with the application of heat. What are requirements of a good boiler? - answer 1. simple
- designed to accommodate expansion and contraction
- adequate steam and water space
- efficient
- responsive to demands
- accessible for cleaning and repair
- safe Name and describe three types of heat transfer used in boiler operation. - answer RADIANT HEAT-is heat radiated from a hot to cold body and depends on the temperature difference and the color of the body that receives the heat. The heat from the sun reaches us by means of radiation. CONDUCTION HEAT-is heat that passes from the gas to the tube by physical contact. The heat passes from molecule of metal to molecule of metal with no displacement of the molecules. CONVECTION HEAT-is heat transmitted from a hot to cold body by movement of the conveying substance. What is a combustion chamber? - answer The area of a boiler where the burning of fuel occurs What is an internally fired boiler and name 4 types. - answer Internally fired boilers are those in which the grate and combustion chamber are enclosed within the boiler shell. Scotch Marine Cast iron package Steam locomotive Vertical fire tube What is an externally fired boiler and name 4 types. - answer Externally fired boiler is a boiler in which the setting, including furnace and grates are separate and distinct from the boiler shell.
What is a longitudinal joint? What is a circumferential joint? - answer A longitudinal joint is a seam running the length of the shell and is butt strap construction or fusion welded. It is above the fire line to avoid overheating. A circumferential joint is a lap joint running the circumference of the joint. What is the difference between a flue and a tube? - answer A tube is 4 inches or less in diameter measured externally. A flue is 4 inches or more in diameter measured internally. What is a dry pipe and where is it located? - answer The dry pipe is a steam separator located within the boiler shell and connected to the steam outlet. Its upper surface is perforated. Steam enters the perforations rapidly changing its direction of flow before entering the steam outlet. This causes droplets and impurities to separate the steam. Describe a scotch marine boiler and how it is fired? - answer A scotch marine boiler is an internally fired self contained horizontal return fire tube boiler. It is a cylindrical shell containing the combustion chamber and tubes that are surrounded by water. How is a sterling boiler suspended? - answer Lugs on the ends of the upper drums rest on the beams of its structure. The lower (mud) drum is suspended from the tubes and is free to move by expansion. Describe the circulation of water within the sterling boiler. - answer Feedwater enters the top rear drum, passes down the rear tubes to the mud drum. Steam and boiler water go up the front banks of tubes to the front and center drums. Circulator tubes allow the boiler water to pass between drums. What does not go out as steam goes back down the rear tubes.
What provisions are made for tube removal on water tube boiler? - answer Some tubes are left out. The tubes are staggered. Sometimes every other row is omitted. What is a water tube boiler? What are five advantages and five disadvantages of a water tube boiler? What are five types of water tube boilers? - answer A water tube boiler is a boiler in which the products of combustion pass around the tubes containing boiler water. Advantages - they are rapid steamers - they use less water - they have less of a chance of exploding - they have no flat surfaces - they have smaller tube sizes Disadvantages - they have elaborate settings - they are field assembled - initial cost per lb. of steam is higher - greater number of openings thus more air filtration needed - need large floor space Four types - B&W - Sterling - Hiene - Riley - Consolidated - F.M. Package - M&H - Cross Drum Straight Tube - DAO Type What is a fire tube boiler? What are five advantages of a fire tube boiler and five disadvantages of a fire tube boiler? Name four types of fire tube boilers. - answer A fire tube boiler is a boiler in which the products of combustion pass through the tubes or flues that are surrounded by water. Advantages - Low cost - small floor space - factory assembled - fast installation Disadvantages - liable to explosions - drums and joint set over the fire - inaccessible for inspection - poor circulation - slow steamer - inefficient
The third type of super heater is a combo of the radiant and the convection. What is an economizer? What is a pre-heater? - answer An economizer is a heat exchanger located in the breaching between the boiler and stack designed to recover waste heat from the products of combustion by pre-heating the feed water. The air pre-heater consists of a series of tubes or plates that have hot gases on one side and incoming air on the other side. Heat in the hot gases leaving the boiler is recovered by the incoming air. What is a water wall? - answer A water wall is a set of tubes containing boiler water, set in the refractory. The water wall absorbs heat that would otherwise be lost. The water wall increases the capacity of the boiler. What is A.S.M.E. and its purpose? What code information is stamped on the boiler? What is an A.S.M.E. stamp? Where are the code markings found on a boiler? - answer A.S.M.E - American society of mechanical engineers It is a code of minimum standards for the safe construction of pressure vessels. Stamped on the boiler shell or plate attached to the shell there will be - the safe working pressure - date of manufacture - name of manufacture - type of material used - hp rating - square feet of heating surface - steam generation in lbs. per hour - fuel designed for The A.S.M.E. stamp will identify the boiler or accessory type.
On a fire tube boiler, it will be located on the right side near the front of the boiler, near the water column. On a water tube boiler, it will be located next to the manhole on the steam drum. What is the cross section of a 1 inch bolt? - answer Diameter x Diameter x .7854 =. What is an alloy? Name five. - answer An alloy is a mixture of two or more metals. Types - brass, stainless steel, cast iron, steel, pewter, Babbitt At what pressure is the use of cast iron fittings permitted? - answer 15 psi or 250 degrees F not to exceed either one What is meant by factor of safety? - answer Factor of safety is the comparison of the tensile strength to the actual working stress. The bursting pressure divided by the working pressure. What is the factor of safety for boilers, flywheels and pipe? - answer New boilers - 4 Pre-owned boilers constructed to A.S.M.E. code is - 5 Flywheels - 3 Pipe - 8 What is a lap joint? What is a butt joint? What is a butt strap joint? - answer A lap joint is when one plate overlaps the other and is jointed. A butt joint is when two ends of the plate meet end to end and are jointed.
For drainage of the top drums and to prevent air pockets in the lower drums. Is it necessary to brace or stay a flat surface? Name three types of stays. - answer Yes, to overcome the force on heads and flat surfaces. Where there are no tubes, braces and stays must be provided to prevent bulging of the boiler plate. Through bolt - Stay bolt - Diagonal stay - Gusset stay Describe a through stay. Why are hollow stay bolts used on water legs? - answer A through stay runs from one tube sheet to the other or one flat surface to another. A rod threaded on both ends is held in place with nuts on the inside tightened against nuts on the outside of the plates. A small hole is drilled into the stay bolt so if it was to fail, it would develop a leak and be detected at once. Describe a diagonal and a gusset stay. Where would each be used? - answer A diagonal stay is made of a flat material similar to the boiler shell and is attached directly to the boiler shell and head or tube sheet. A gusset stay consists of boiler plate riveted to the shell and head or tube sheet by means of angle iron. They are more rigid. Both are used to brace right angle surfaces. Why are handholes and manholes made oval instead of round? What are minimum sizes for manhole and handhole openings? - answer So they can be inserted into and removed from their respective openings in the boiler.
Manhole 11 x 15 or 10 x 16 Handhole 2.75 x 3. What is thermal efficiency and what is a good percentage? - answer It is the ratio of heat supplied by fuel to heat absorbed by the boiler. A good percentage is 85% How do you determine boiler capacity and what is boiler heating surface? - answer Total heating surface determines the capacity of the boiler. Heating surface is any area that has hot gases on one side and boiler water on the other. It is measured from the fire side. What is furnace volume? Is furnace volume measured in square feet or cubic feet? - answer Furnace volume is the space available for complete combustion of the fuel before the products of combustion enter the heat absorbing section of the boiler. This varies with the type of fuel used. Furnace volume is measured in cubic feet. What is superheated steam? Does its temperature rise? - answer Superheated steam is steam that has been heated to a high temperature, but its pressure remains the same. Yes superheated steams temperature does rise.
Yes - Secondary air is introduced above the fuel bed to burn combustible gases. What are the three T's of combustion? - answer Time- enough time must be allowed for the fuel to be fully burned before the hot gases of combustion come into contact with boiler tubes. Temperature- combustion must occur in a high temperature zone to make sure the fuel in the flue gases is sustained above the ignition temperature until fully consumed. Turbulence- a turbulent area in the furnace allows the air and fuel to be fully mixed. In order to be completed, each molecule of fuel must come into contact with an adequate number of oxygen molecules. Define PSI, PSIG, and PSIA - answer PSI- pressure exerted on a surface PSIG- pressure read on a gauge PSIA- gauge reading plus atmosphere Could too much secondary air have a bad effect on the efficiency of a boiler? - answer YES Excess secondary air will not enter into the reaction, but will pass through the furnace wasting heat out the stack What percent of air is oxygen by volume and what by weight? - answer By volume oxygen is 21% By weight oxygen is 23% Define Perfect, Complete and Incomplete combustion. - answer Perfect - burning all the fuel using only the theoretical amount of air Complete - Burning all the fuel using more than the theoretical amount of air Incomplete - when a portion of the fuel remains unburned because of insufficient amounts of air
What is excess air? - answer The amount of air in excess of what is theoretically needed for complete combustion. In a flue gas analysis, what do you consider a good percent of CO2?
- answer 12% - 15% With 20% ideal, but mostly unattainable How is the density of smoke measured? - answer With an opacimeter or a ringleman chart What grades of smoke are allowed in boiler operation? - answer No darker than grade 1 for more than 5 minutes per hour and no more than 3 times in a 24 hour period What are 7 heat losses in a boiler? - answer Moisture in the air Moisture in the fuel Moisture formed in the burning of hydrogen Incomplete combustion Unburned carbon in the ash Heat carried away in dry flue gases Radiation and other losses What is the heat content of one pound of good coal and one pound of carbon? - answer Coal - 13,000 - 14,000 BTU's Carbon - 14,540 BTU's What is an Orsat Apparatus? Where is it used? Why is it used? - answer A flue gas analyzer to determine the amounts of CO, CO2, and O2 in flue gasses. Combustion gasses are sampled from the last pass or the breeching.
