Ch. 1

Question 1

157. Packaged watertube boilers capacities range from?
     a. 2300 kg to 65000 kg per hour
     b. 500 kg to 100 mg per hour
     c. 15 psi to 15000 kg per hour
     d. 65000 to 100000 kg per hour

Answer 1

a. 2300 kg to 65000 kg per hour

Question 2

158. The main advantage of the packaged boiler is its _____ _____.
     a. small size
     b. compact design
     c. low cost
     d. quality steam

Answer 2

c. low cost

Question 3

159. Field erected boilers have outputs of?
     a. 75000 kg/h
     b. 100000 kg/h
     c. 100 mg/h
     d. 150000 kg/h or more

Answer 3

d. 150000 kg/h or more

Question 4

160. One square metre of heating surface equals 10 kilowatts. The heating surface of a boiler must be determined by computing the area of the surface involved in square metres and where a computation is to be made of a curved surface; the surface having the greater radius shall be taken.
     a. True
     b. False

Answer 4

a. True

Question 5

161. Where electric power is used as the heating source, the boiler rating shall be the maximum kilowatt rating of the ______ ______.
     a. power plant
     b. heating element
     c. boiler wiring
     d. MCC

Answer 5

b. heating element

Question 6

162. Where the boiler provides the entire steam supply to an electric generating unit, the output of the boiler is expressed in terms of power output of the generator (for example a 300 megawatt boiler).
     a. True
     b. False

Answer 6

a. True

Question 7

163. The downcomers are located in the ______ regions of the boiler, or external to the furnace altogether. The risers are located in the ________ zones of the boiler, being exposed to radiant heat of the furnace or to the very hot flue gases near the furnace.
     a. back, front
     b. cooler, hottest
     c. water, furnace
     d. drum, radiant

Answer 7

b. cooler, hottest

Question 8

164. Most downcomers run horizontally between the steam drum and the mud drum.
     a. True
     b. False

Answer 8

b. False

Question 9

165. The steam separating equipment separates the _______ from the steam/water mixture.
     a. water
     b. steam
     c. impurities
     d. water droplets

Answer 9

b. steam

Question 10

166. There are several factors that influence the natural circulation in a watertube boiler. These are:
     a. The height of the steam drum above the bottom drum or header.
     b. The amount of heat applied to the tube. The hotter the tube becomes, the more steam bubbles are formed, creating more mass differential and thus more circulation.
     c. The operating pressure of the boiler. As boiler pressures increase, the density of the steam increases
     d. The cleanliness of the tubes can also affect circulation.
     e. All of the above

Answer 10

e. All of the above

Question 11

167. The purpose of the downcomer is to supply:
     a. Hot water to the steam drum
     b. Cool water to the steam drum
     c. Cool water from steam drum to rest of boiler
     d. Steam to steam drum
     e. Boiler feed water to the boiler

Answer 11

c. Cool water from steam drum to rest of boiler

Question 12

168. These types of boilers (A, D, and O) have furnaces cooled by _________ lining the furnace walls.
     a. watertubes
     b. fans
     c. desuperheaters
     d. air circulation

Answer 12

a. watertubes

Question 13

169. In the A, D & O type boiler steam bubbles form in the hottest tubes and rise to the steam drum, where the steam is separated out of the water and steam mixture. Circulation is maintained by water returning to the mud drum through the cooler tubes. The hotter tubes, risers, are the ones in the radiant area of the furnace and the hottest areas of the generating bank of tubes.
     a. True
     b. False

Answer 13

a. True

Question 14

170. A steam generating unit consists of a number of elements all of which contribute to the production of steam. The elements of a typical steam generator include:
     1) Boiler
     2) Superheater
     3) Ash removal equipment
     4) Reheater
     5) Economizer
     6) Steam piping
     7) Air heater
     8) Fuel equipment
     9) Draft fans
     a. 1, 2, 7, 8, 9
     b. 1, 2, 4, 5, 7, 8, 9
     c. 3, 4, 6, 7, 8
     d. 1, 2, 3, 4, 5, 7, 8, 9

Answer 14

d. 1, 2, 3, 4, 5, 7, 8, 9

Question 15

171. In steam generating units the feed-water entering the boiler section first passes through the __________ section where it is heated by the combustion gases leaving the boiler.
     a. furnace
     b. economizer
     c. boiler drum
     d. superheater

Answer 15

b. economizer

Question 16

172. Combustion air for the burners is preheated to ______in the air heater section by combustion gases leaving the economizer section.
     a. 150 °C
     b. 100 °C
     c. 350 °C
     d. 500 °C

Answer 16

c. 350 °C

Question 17

173. Generally two types of draft fans are used. A _____ ____ fan supplies air to the air preheater. The preheated air (350°C) for combustion goes to the coal pulverizers and to the burners. An ______ ____ fan exhausts the combustion gases (170°C) from the air heater to the stack.
     a. center mounted, external mounted
     b. forced draft, induced draft
     c. induced draft, forced draft
     d. turbine draft, ejection draft

Answer 17

b. forced draft, induced draft

Question 18

174. Natural circulation in a boiler depends upon the ___________ in the density of a column of water and the density of a column containing a steam/water mixture.
     a. amount
     b. mass
     c. difference
     d. density

Answer 18

c. difference

Question 19

175. The difference in density between water and saturated steam becomes progressively less with increased pressure and disappears altogether at the critical pressure _______ .
     a. 22106 kPa
     b. 15000 kPa
     c. 10000 kPa
     d. 25000 kPa

Answer 19

a. 22106 kPa

Question 20

176. Steam generators operating above critical pressure are said to be ______-critical and steam generators operating below critical pressure are classed as ____-critical.
     a. sub , super
     b. super, sub
     c. normal, pre
     d. high, low

Answer 20

b. super, sub

Question 21

177. The advantage of forced circulation in a boiler is a _________ flow in all tubes.
     a. negative
     b. greater
     c. positive
     d. mass

Answer 21

c. positive

Question 22

178. The disadvantages of forced circulation in a boiler are the ______ _____ of equipment, pumps, piping, etc.
     a. greater use
     b. increased costs
     c. higher maintenance
     d. numbers of

Answer 22

b. increased costs

Question 23

179. The main feature of a Controlled Circulation Boiler is a (circulating) pump, which is used to provide circulation.
     a. True
     b. False

Answer 23

a. True

Question 24

180. Not all Once-through boilers use forced circulation.
     a. True
     b. False

Answer 24

b. False

Question 25

181. The arrangement of a once through boiler has no drums. The feed water is heated and then evaporated and superheated in ______ ______ through the unit.
     a. two passes
     b. one passage
     c. 3 passes
     d. 4 passes

Answer 25

b. one passage