4. Translate from Russian into English using the vocabulary of the Unit.

1. Процесс удаления влаги из древесины испарением называется сушкой.

2. Предметы, изготовленные из плохо высушенной древесины, часто усыхают и разваливаются на части.

3. Под влиянием циркулирующего воздуха влага, содержащаяся в древесине, испаряется.

4. Одна из главных задач сушки древесины – уменьшить изменения ее формы и размеров в результате коробления и растрескивания.

5. Недостаточное внимание к сушке древесины может привести к повышенному расходу древесины и бесполезным затратам.

6. Испарение влаги должно быть одинаковым по всем направлениям.

7. Для сушки пиломатериалы укладываются в штабель.

8. Столбы обычно сушатся на воздухе.

9. Часто практикуется сочетание воздушной сушки с последующей кa-мерной сушкой.

10. Влагосодержание в древесине следует уменьшить до определенной величины в зависимости от предназначения материала.

11. Срок годности древесных изделий значительно сокращается, если древесина плохо высушена.

12. Мебель, изготовленная из сырой древесины, разваливается через несколько месяцев.

V. Speak about:

1. The advantages of drying lumber.

2. The methods of drying.

Unit 7

Infinitive. Revision

Grammar:

Air-Drying Process

I. Answer the questions:

1. Why is timber dried?

2. What are the most common methods of drying?

3. What is air-drying?

2. Read the text and try to understand it.

Timber has been air-seasoned since time immemorial. The great merit of air-seasoning lies in fact that no special apparatus is required. If a tree is felled and left to lie in the forest, will it dry? If the tree is small and the trunk is not resting on the ground, the answer is: yes, in time. If a tree is a normal-sized one, very little drying will take place, and that will be confined to the outer layers and the ends of the tree. Moreover, as the tree lies in the forest it will be open to attack from fungi and beetles and will almost certainly become practically worthless long before it is even partially dried.

The air-drying of lumber involves exposing piles of stickered lumber to the outdoor air. The drying rate and the minimum moisture content attainable at any time in any place depend almost entirely on the weather. Green lumber dries because air conducts heat to the wood surface and carries away the evaporated moisture. Thus the air must move within and through the lumber in the pile. As warm, dry air enters the lumber pile, it takes up moisture from the wood and the air temperature decreases. As the cool, damp air leaves the pile fresh air enters and drying continues. The way air moves within a lumber pile depends on the construction of the pile, its location within the yard, and the yard layout and arrangement.

The method of stacking sawn timber for air-drying is well known to depend on the sizes to be dried and on the ultimate use, to which timber is to be put. Boards are usually placed as close edge to edge as possible in each course of a package, and there is limited opportunity for the air to drop downward through the package as it cools and becomes heavier. Consequently, the air must move laterally across the boards. The main object in piling is to secure free passage of air to all parts. That’s why each successive layer of timber is separated by strips of wood known as stickers, the thickness of which regulates the rate of air flow. The stickers should be of sound, seasoned timber. When a stack is dismantled the stickers should be collected, bundled and stored for further use. The most suitable thickness for stickers depends on the thickness of timber to be seasoned.

The foundation under the pile should be reasonably high to allow the prevailing winds to create a brisk air movement under the piles. Pile foundation should not obstruct air flow, and weeds or other debris should not be allowed to block the air passage. For the foundation of stacks, balks of timber are commonly used, but concrete, bricks or even wooden piers are better as they offer less resistance to the free circulation of air under a stack.

The drying efficiency of a yard depends to some extent on how well the ground surface is graded, paved and drained. If water stands in a yard after a rain, it will decrease the drying rate and increase the risk of developing stain. The yard should be kept clean.

Some woods dry quickly, others slowly. Softwoods and some lightweight hardwoods dry rapidly under favourable air-drying conditions. The heavier hardwoods require longer drying periods to reach the desired average moisture content. Specific gravity of wood can guide estimations of drying rates or overall drying time.

General understanding

Answer the questions:

1. Is air-seasoning one of the oldest methods of drying?

2. What is the greatest advantage of air-seasoning?

3. Can the felled trees dry in the forest?

4. What is air-drying?

5. What does the drying rate depend on?

6. What does the movement of air depend on?

7. How is lumber stacked in a pile?

8. What is the main object of piling?

9. What are the main requirements to pile foundation?

10. What does the drying efficiency depend on?