XIX. Read the text and find the additional information about BLEVEs

In most BLEVEs, the container fails at the top, where it is in contact with gas. The metal stretches, thins out, and tears lengthwise.

The magnitude of.the explosion (BLEVE) depends mainly on how much liquid vaporizes when the container fails and on the weight of the container pieces. Most BLEVEs occur when containers are from slightly less than half full to about three-fourths full of liquid. A small, uninsulated container can experience a BLEVE in a very few minutes, and a very large container in a few hours, in the absence of water-cooling.

Uninsulated liquefied gas containers that are exposed to fire can be protected from BLEVEs by applying water. A film of water should be maintained on the upper portion of the container, the portion that is in the internal contact with vapour.

XX. Translate the text from Russian into English in writing.

1. Нефтяной сжиженный газ, такой как пропан и бутан, хранят в жидком состоянии.

2. Для этого во всем мире используют цистерны и вагон-цистерны.

3. Такие цистерны всегда оборудованы предохранительными клапанами.

4. Обычно опасность возникновения утечки газа или взрыва невелика.

5. Однако аварии могут случаться.

6. Когда две вагон‑цистерны сталкиваются (collide), сжижженный газ вытекает и испаряется, образуя облако в высшей степени горючего пара.

7. Достаточно единственной искры или небольшого огня, чтобы горючий газ дал обратную вспышку вытекающей жидкости (flash back to the leaking liquid).

XXI. Translate the microtext:

Pressure

Gases are made up of atoms and molecules, which are in constant and rapid motion. The atoms and molecules are constantly hitting the walls of the gas container. In doing so they exert pressure on the walls.

Gases have no definite shape or volume. The shape and volume of a gas depend on its container. Compared with solids and liquids, the molecules of a gas are relatively far apart. Hence they can be compressed, or forced into a smaller space. But if the volume of a gas is decreased, its pressure increases, because the molecules hit the walls more often and more rapidly.

The more a gas is compressed, the greater its resistance to compression. If a large amount of gas is forced into a small space, it becomes difficult to compress further. Under very high pressure, compressed gas can be used for transmitting power.

As gas pressure is increased, the molecules are forced closer together. If this continues, the molecules eventually become attached to one another. At this point, the gas changes into a liquid.

The pressure of a gas varies with temperature. Pressure is in direct proportion to absolute temperature, since the higher the temperature, the more rapid the motion of the molecules, and consequently the greater the pressure exerted on the walls of the container. Conversely, the higher the pressure of a gas, the higher its temperature. When a gas is compressed, it becomes hotter.

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