VI. Прочитайте о преимуществах и недостатках огнетрубных и водотрубных котлов, затем заполните таблицу.

The advantages of the fire-tube boiler are: ease of maintenance and repair, ability to use feed water of doubtful quality, and adaptability to practically any fuel.

As disadvantages, they require large quantities of boiler water, are heavy and bulky, cannot raise steam quickly, and extremely hazardous if damaged, due to the large quantities of water and steam contained in the shells.

The strong features of the water-tube boiler, as compared with the fire-tube types, are: saving in space, safety in the event of serious rupture, saving in weight, the possibility of using high pressure and temperatures, greater mechanical flexibility, rapid steam raising. The failure of a single part is not apt to cause an explosion nor any damage beyond the damage to that part.

Their more undesirable limitations are that their operation requires a greater degree of skill and engineering knowledge, and that they require for operation pure, fresh water only.

Fire-tube boiler

ADVANTAGES	DISADVANTAGES
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2.	2.
3.	3.
	4.

Water-tube boiler

ADVANTAGES	DISADVANTAGES
1.	1.
2.
3.
4.	2.
5.
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Part 2

Давайте поговорим.

I. Прочитайте и переведите следующие диалоги.

Dialogue 1.

Visitor: What type of boiler have you on board?

You: A water-tube boiler. It is a heart of steam power plant. We use steam for our fish factory and domestic needs.

Visitor: As far as I know there are two types of steam boilers: the fire-tube and the water-tube ones.

You: You are quite right. But water-tube boilers have replaced fire-tube boilers for generating steam for main engines.

Visitor: Why so?

You: I think fire-tube boilers are heavy and bulky. Besides they are extremely hazardous if damaged due to the large quantities of water and steam contained in the shells.

Visitor: And what about the water-tube boiler?

You: Oh, they have some advantages. The strong features of the water-tube boiler as compared with the fire-tube boiler are: saving

in space and weight, greater mechanical flexibility, rapid steam raising, safety in the event of serious rupture due to small water content.

Visitor: So, there is a difference in the design of these two types of boilers.

You: It goes without saying. A fire-tube boiler is a tank boiler in which the water is outside the tubes and the hot gases pass through the smoke tubes. As for water-tube boilers the water circulates through the boiler tubes and hot gases surround these tubes.

Visitor: I see. And what are the basic parts of the water-tube boilers?

You: They are: shell, furnace, burners, water and steam drums, tube bank, economizer, superheater and some others. Have you got any more questions?

Visitor: No, thanks for your time.