2.Scan for the details and circle the correct letter.

• Stress corrosion cracking a/(SCC),b/(Scc),c/(SCc) is the

• unexpected sudden failure.

• SCC is highly chemically a/simple, b/specific, c/alone in that certain alloys.

• SCC only exposed to a small number of a/total, b/physical, c/chemical environments.

• a/ Metal, b/ glass, c/ paper parts with severe SCC can appear bright and shiny.

• The stresses can be the result of the crevice loads due to stress a/concentration, b/amount.

3.Choosc the words from the box to complete sentences.

environment	mildly corrosive	factor
small number	microscopic cracks	crevice loads

1. Stress corrosion cracking is the unexpected sudden failure of normally ductile metals subjected to a tensile stress in a corrosive .

2. SCC is highly chemically specific in that certain alloys are likely to undergo SCC only when exposed to a of chemical environments.

3. The chemical environment that causes SCC for a given alloy is often one which is only to the metal

4. otherwise.

5. Hence, metal parts with severe SCC can appear bright and shiny, while being filled with .

6. This ____ makes it common for SCC to go undetected prior to failure.

7. The stresses can be the result of the _____________ due to stress concentration.

4. Ask 4 types of the questions to the sentences:

1. The highly active chemicals are needed to produce catastrophic cracking.

2. The stresses can be the result of the crevice loads due to stress concentration.

3. The residual stresses can be relieved by annealing.

5. Discuss the answers to the questions with your group mates.

1. Is the stress corrosion cracking the unexpected sudden failure of normally ductile metals?

2. What is the highly chemically specific in the certain alloys?

3. When did SCC expose to a small number of chemical environments?

4. 4 What parts can appear bright and shiny?

5. The specific environment is of crucial importance, is not it?

6. Make up 5 sentences using following words:

Metals, chemicals, parts, bright, shiny, microscopic, common, importance, catastrophic, result.

7. How do you say these expressions in your language?

• Ductile metals

• Tensile stress

• Chemical environments

• Microscopic cracks

• Crucial importance

• Small concentration

• Catastrophic cracking

• Stress concentration

• Residual stresses

• Annealing

Unit 20

Welding - Safety Rules.

1.Read, translate and remember the main welding rules:

WELDING

CAUTION: Welding can be dangerous. Any of these accidents might happen to you:

( a ) you could be blinded by sparks;

( b ) you could get an electric shock;

( c ) your face, body, arms, legs or feet could be burnt;

( d ) there could be a fire in the workshop.

PROTECTIVE CLOTHING

1. A mask or helmet must be worn in electric arc welding. (In gas welding, goggles can be used.)

2. Clothes must be kept dry and clean.

3. Thick, heavy boots must be worn.

4. These must be made of some insulating material such as rubber.

5. Gloves, and apron and a cap must be worn.

6. Overalls must have long sleeves and no pockets or cuffs.

WORKSHOP

1. The floor must be mode of concrete.

2. There must be a metal container on the floor for the sparks.

2. Answer these questions:

1. Why must you wear a mask or helmet? (ANSWER: 'Because you could / may / might')

2. Why must you keep clothes dry?

3. Why do you have to wear rubber boots?

4. Why must you wear an apron and cap?

5. Why must the floor be made of concrete?

6. Why do you need a metal container on the floor?

3. Complete the sentences:

1. Gloves, and apron and a cap must....

2. Overalls must have long sleeves and ....

3. A mask or helmet must be worn in ...

4. In gas welding, goggles ...

5. Clothes must be kept dry ...

6. Thick, heavy boots must...

4. Make up the sentences:

1. The, concrete, floor, of, must, be, made.

2. There, sparks, must, the ,be, for, a, metal, on, the, floor, container.

3. Dangerous, welding, can, be, a.

4. You, sparks, could, be, blinded, by.

5. Shock, could, get, you, an, electric, shock.

5. Find the Ukrainian equivalents:

• Welding

• Safety rules

• Protective clothing

• Workshop

• Helmet

• Metal container

• Insulating material

• Heavy boots

• Rubber boots

Unit 21

Boilers

1.Read and translate the text :

Boilers.

The function of the boilers is to furnish a supply of steam at the required pressure, of quality as nearly dry as possible; There are many different types of boilers and in the selection of one to work under given condition attention must be paid to :

• The suitability of the design for safety carrying the proposed steam pressure;

• The efficiency with which the potential energy of the coal or other fuel is converted into heat in the steam;

• Accessibility, both externally and internally;

• Space occupied;

• Speed with which steam can be raised, stating with cold water and fires out.

Boilers are either fire-tube or water-tube. In fire-tube boilers, the furnace gases are led through tubes around which water circulates. In water-tube boilers, the water occupies the interior of the tubes and the gases pass over them externally. In general, water-tube boilers are more suitable than fire- tube boilers for the generation of steam at very high pressures and for the fulfillment of condition (5) above. Fire-tube boilers are suitable for steady working at pressures up to say 200 lbs. per square inch, and can be constructed so as to fulfill condition (3) above very completely. The efficiency in well-designed boilers of both types is about the same. Water- tube boilers take up less space than fire -tube boilers of the same power.