Complete the sentences

1. Boiler feed water is required for ….

2. Untreated water leads to ….

3. Dissolved salts may lead to such problems as ….

4. An excess of alkaline salts in a boiler causes ….

5. Foaming occurs when ….

6. Such metal salts as … make up the 'hardness' of the water.

TEXT C

CONTAMINATION OF FEED water

The quality of boiler water plays an important role in boiler operation. Contamination of boiler water leads to several types of problems, including the main ones – corrosion and scale formation.

Inside the boiler system, the boiler feed water passes through a series of tubes and equipment. The feed water is always chemically treated to reduce the effects of harmful minerals and gases.

The main problem starts when a lot of this boiler feed water is lost through leakages and processes such as boiler blow down, soot blowing etc., and make-up water is added to compensate this loss. This make-up water brings in a lot of the impurities into the boiler system.

How is the make-up feed water contaminated?

Boiler feed water is mainly taken from the fresh water generator. The sea water contains a large amount of salts and other dissolved minerals and gases. Many of them are harmful and eventually lead to boiler problems.

Salt deposits act as insulators and lower the heat transfer rate.

The insulating effect of deposits also causes the boiler metal temperature to rise and lead to tube-failure by overheating.

Large amounts of such deposits throughout the boiler can reduce the heat transfer and decrease the overall boiler efficiency.

Vocabulary

contamination, v загрязнение

treat feed water подготавливать питательную воду

harmful, adj вредный, опасный

leakage, n утечка, течь

boiler blow down продувание котла

soot blowing сажеобдувание

fresh water generator опреснитель; опреснительная установка

dissolve, v растворять

salt deposits отложение солей

insulator, n изолятор

heat transfer rate скорость теплоотдачи

overall, adj общий

E X E R C I S E S

1. Change these sentences using the modal verbs may, can, must:

Model. Priming is due to high ratings. Priming may be due to high ratings.

1. Foaming is due to the presence of dirty water in the boiler.

2. Oil in the feed water is very injurious to the boiler.

3. Priming is also due to a poorly designed steam drum.

4. Acids are neutralized by the addition of sodium carbonate.

5. A little of the chemicals is added at a time.

2. Change these sentences into the passive:

Model. Chemicals remove scale from the boiler. Scale from the boiler is removed by chemicals.

1. The addition of alkalis prevents scale formation.

2. The presence of oils in solution causes foaming.

3. Some of the salts produce a soft sludge.

4. The chlorides of sodium and magnesium and the sulphate of iron cause corrosion.

5. We may neutralize acids by the addition of sodium carbonate.

UNIT 6

TEXT A

BOILER PARTS. THE FURNACE

A furnace provides steady burning of fuel.

The furnaces of marine water-tube boilers are lined with refractory firebrick backed up by the insulating bricks. This brickwork acts as furnace insulation and also, by maintaining a high furnace wall temperature, assists combustion.

Water walls are used in water-tube boilers to contain the heat of the furnace and reduce the amount of refractory material required. Water walls consist of a number of tubes and extend along the sides of the furnace setting.

To provide the efficient combustion process of burning oil fuel, a certain set of conditions is necessary: maintenance of high furnace temperature, provision of continuous oil fuel and air supply and removing products of combustion.

The oil is first heated in steam or electric fuel oil heaters. This reduces its viscosity and makes it easier to pump, filter, and finally to atomize. The heated oil passes through the burners where it is atomized; this process breaks it up into a fine spray of droplets presenting a very large surface area of oil to the combustion processes.

Different types of burners have been designed for burning liquid fuel. Mechanical oil burners and steam-assisted ones are employed to obtain efficient atomization. Mechanical atomizing oil burners may be classified according to their method of atomization as centrifugal atomizers and rotary cup atomizers.

Steam-assisted oil burners are widely spread in marine practice. Their advantages are high quality atomization and a wide range of fuel oil feed control.

Vocabulary

steady, adj устойчивый

firebrick, n огнеупорный кирпич

brickwork, n кирпичная кладка

insulation, n изоляция

assist, v помогать; способствовать

water wall экран из водогрейных трубок

amount, n количество

setting, n кладка; обмуровка

set of conditions комплекс условий

maintenance, n поддержание

atomize, v распылять; тонко измельчать

tobreakup разбивать(ся)

droplet, n капля

surface, n поверхность

mechanical oil burner механическая форсунка

steam-assisted oil burner паромеханическая форсунка

centrifugal atomizer центробежный распылитель

rotary cup atomizer форсунка с вращающимся распылителем

range, n диапазон

oil feed подача топлива

E X E R C I S E S

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