| the same | space | internally |
| fires out | steam pressure | potential energy |
1. The suitability of the design for safety carrying the proposed.
2. The efficiency with which the of the coal or other fuel is converted into heat in the steam;
3. Accessibility, both externally and _______.
4. ______ occupied;
5. Speed with which steam can be raised, stating with cold water and _______.
6. The efficiency in well-designed boilers of both types is ________.
Now try to tell the gist of the text in 10 sentences. Use the questions from Ex.2 to help you.
Complete the dialogue and perform it in pairs.
- What do you know about the difference between water-tube and fire- tube boilers?
- Are they the same?
- What is the efficiency?
- How can they be worked?
- What happens with water-tube and fire-tube boilers at very high pressures?
Unit 22
Water-Tube Boilers.
1. Read and memorize the following expressions:
Ø Hand in hand - одночасно, паралельно
Ø Included tubes expanded - труби, що нахилились, і перейшли у водяні колектори
Ø Front and rear - спереду і ззаду
Ø Steam and water-circulating tubes - парові та водопровідні труби
Read and translate the text.
Water-Tube Boilers
Inherent design features have permitted a much greater development of boilers of the water-tube type than has been possible with fire-tube type. Present-day water-tube boilers are built in small and large capacities even up to single units that produce over a million pounds of steam an hour. Super heaters are used with these boilers to raise the temperature of the steam above saturation temperature to final temperature to final temperature as high as 950 F.
Horizontal inclined straight-tube boilers may have either longitudinal or cross drums and may have either box-headers or sectional headers into which the tubes are rolled.
Longitudinal - drum straight-tube boilers have inclined tubes expanded front and rear into water legs that connect to a horizontal drum parallel to the tubes. Small boilers have one drum. Lager boilers, more than about 14 tubes wide have two or more parallel drums.
Box-type water legs are formed of steel plate riveted together to form boxes about 8 in. deep. The water leg at the high end of the tubes has a flanged semicircular throat so it may be riveted directly to the drums. Sectional - type water legs are sinuous-shaped wrought-steel headers into which usually one vertical row of staggered tubes are expanded. Sectional headers are vertical and each is connected to the drum by one or two short tubes.
Straight-tube boilers usually have 4-in. diameter tubes, but when the header is used 3-in. diameter tubes are employed. Heat transfer is somewhat better with small tubes, but as tube diameter decreases, the number of headers required in a boiler of given surface increases.
Cross drum straight-tube horizontal-inclined boilers have the same arrangement of straight tubes as the longitudinal - drum types but the drum is placed at right angles.
Location of the super heater is largely determined by the desired final steam temperature and plays an important role in the general arrangement of the boiler.
Bent-tube boilers all have one or more top steam drums and a single bottom or mud drum.
Complete the following sentences.
1. Present-day water-tube boilers are built in small and large capacities...
2. Super heaters are used with these boilers to raise the temperature of the steam...
3. Horizontal inclined straight-tube boilers may have either longitudinal or cross drums and may have either box-headers...
4. Lager boilers, more than about 14 tubes wide have two or...
5. Box-type water legs are formed of steel plate riveted together to form boxes...
4. Make up 5 sentences using following words:
| Boilers, box-headers, tube, water leg, steam drum, temperature, diameter. |
