V. Read and translate the following text. Materials

The first pipe line was manufactured from wrought iron. Since the end of the last century, when steel became available in bulk and at prices considerably below those of wrought-iron, this material replaced wrought iron almost completely. There are different grades or types of steel.

The chemical composition and physical properties of steel depend upon different methods of its manufacture and upon certain elements other than carbon, added during its manufacture. At the present time for the manufacture of pipes medium carbon steel is usually used, though high tensile steel has been utilized for exceptional circumstances and for high pressure lines. Other materials being used for pipe lines include aluminium, titanium and their alloys.

When two or more metals are alloyed they form a new metal which is called an alloy. Steel is often alloyed by the addition of other metals, as nickel, chromium, manganese, etc., to increase its strength and toughness and increase its life by increasing its corrosion resistance properties. In general corrosion resistance increases with the chromium content and decreases as carbon content rises. Unfortunately, most corrosion-resisting alloys of steel are unsuitable for oil and gas pipe, because of the following:

1) they are too costly;

2) difficulty is experienced in working with them because of hardness, brittleness and poor weldability. With the exception of some brass (copper and zink) fittings alloy combinations are not extensively used in gas and oil industry for pipe making. Iron and steel pipes are most commonly used because of their mechanical strength and reasonable price as compared to pipe made from other metals.

In past few years plastic pipes are known to have found wide application. Main use so far is in replacement or insertion into existing service. Biggest advantages of plastic pipe are resistance to corrosion and labour savings. (due to light weight and simple method of joining). The main drawback or disadvantage remains lower mechanical strength and limited temperature range.

Here is how plastic pipes rank in order of popularity in the gas industry: polyvinylchloride, polypropylene, cellulose acetatbutyrate, and polyethylene. A promising newcomer is polyacetal pipe.

VI. Answer the following questions. Use the questions as a plan for your retelling of the text.

1. What was the first pipe line manufactured from?

2. What material replaced wrought-iron?

3. When did steel become available in bulk?

4 What grades of steel are used for manufacturing pipe lines?

5. What other materials are used for the construction of pipe lines?

6. What is an alloy?

7. Why is steel often alloyed with other metals?

8. Why are the most alloys unsuitable for oil and gas pipes?

9. What new materials have found wide application for the production of pipes?

10. What are the advantages of plastic pipes?

VII. Translate the following sentences. State the functions of the Infinitive.

1. То solve this problem is extremely important. 2. To solve this problem we had to make a great number of experiments. 3. The problem to be solved is very important. 4. The engineers had to solve many problems before designing this machine. 5. This worker is too inexperienced to solve this problem without any help. 6. To obtain corrosion-resistant material is of extreme importance for pipeline construction. 7. The scientists are trying to obtain new materials for pipe line construction. 8. To obtain accurate results it may be necessary to use a number of gauges. 9. The amount of polonium to be obtained from a uranium mineral can be simply calculated.

8. Make the four forms of the verbs:

to vary to lay

to withstand to draw

to meet to dig

to string to know