upStationary Grade 3 Engineering License Exam - Q & A , Complete Solutions How can you lose your license? 1) drinking on the job 2) sleeping on the job 3... [Show More] ) negligence 4) unsafe work 5) signing a falsified license application for someone 6) failing to renew your license annually What must you do if you change jobs? notify city hall if you change jobs, address or retire Why should you do rounds? Find and correct problems to prevent breakdowns. Keeping permanent records will make it easy to forecast most breakdowns because you will get to know equipment What is a steam boiler? closed vessel, PARTIALLY FILLED WITH WATER, under pressure that transforms water to steam with the application of heat. What are the requirements of a good boiler? 1) simple 2) designed to accommodate expansion and contraction 3) adequate steam and water space 4) efficient 5) responsive to demands 6) accessible for cleaning and repairs 7) safe Name and describe 3 types of heat transfer used in boiler operation 1) RADIANT HEAT - transmitted from hot body to a cold body by means of direct radiation (heat from sun reaches us by radiation) 2) CONDUCTION - physical contact (coffee cup is heated by conduction when hot coffee touches the cup) 3) CONVECTION - carried along by a moving part such as air or water (your living room is heated by warm air from your furnace in another location What is a combustion chamber? the area of the boiler where COMPLETE burning of the fuel occurs What is an internally fired boiler? Name 4 types Those in which the grate and combustion chamber are enclosed within the boiler shell. 1) Scotch marine 2) Vertical firetube 3) Locomotive 4) Cast iron package boiler What is an externally fired boiler Name 4 types The setting, including the furnace and grates is separate and distinct from the boiler shell. 1) horizontal return tubular (HRT) set in brick 2) some watertube 3) cast iron set in brick 4) Stirling boiler 5) Heine boiler What is a crown sheet and its purpose? What is a tube sheet and its purpose? In a vertical firetube boiler holds the tubes and is thicker because it is exposed to the fire. holds the tubes and does not see the fire What is a waterleg on a boiler? space between the outer shell and the furnace containing boiler water. it absorbs heat that would be wasted and increases the capacity of the boiler. the surfaces are flat and must be stayed. Is an HRT Boiler set level or inclined and why? Are HRT Boiler tubes set level or inclined and why? INCLINED 1-3" front to rear to permit drainage and removal of water impurities INCLINED with the boiler Name 2 ways to support and take care of expansion of an HRT Boiler Which way is best? 1) Suspended from hangars and supported by overhead beams 2) Set on saddles equipped with rollers to permit movement of the boiler as it expands and contracts Suspended from hangars and supported by overhead beams is best because it works no hardship on the furnace walls What is a longitudinal joint? What is a circumferential joint? LONGITUDINAL JOINT = seam running the length of the shell and is butt strap construction or fusion welded. it is above the fireline to avoid overheating. CIRCUMFERENTIAL JOINT = lap joint running the circumference of the drum What is the difference between a flue and a tube? 1) Flue - 4" or more in diameter measured internally 2) Tube - 4" or less in diameter measured externally What is a drypipe and where is it located? 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 causing droplets and impurities to separate from the steam before entering the steam outlet. Describe a Scotch Marine Boiler? How it is fired? It is an internally fired self-contained horizontal return firetube boiler. It is a cylindrical shell containing the combustion chamber and tubes that are surrounded by water. How is a Stirling Boiler suspended? 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 Stirling Boiler feed water enters the top rear drum, passes down the rear tubes to the mud drum. steam and boiler water go up the front and center tubes to the front and center drums. CIRCULATING TUBES allow boiler water to pass between the drums. what does not go out as steam, goes back down the rear tubes. What provisions are made for tube removal on water boilers? 1) some tubes are left out 2) the tubes are staggered 3) sometimes, every other row is omitted 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: 1) elaborate settings 2) field assembled 3) initial cost per pound of steam is higher 4) greater number of openings thus more air infiltration 5) require more floor space TYPES: 1) B.&W. 2) Stirling 3) Heine 4) "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 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 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. ADVANTAGES: 1) increases efficiency of the boiler 2) delivers dryer steam 3) dryer steam can be transmitted long distances with minimal heat loss 4) 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 a 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 [Show Less]
