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

1. Эффективная атмосферная сушка помогает снизить потери конечных продуктов.

2. Планировка биржи зависит от климатических условий.

3. Во время сушки движение воздуха через штабель должно быть достаточным, чтобы удалить испарившуюся влагу.

4. Для воздушной сушки ширина штабеля колеблется от 1 до 2,4 метра.

5. Должный контроль за влажностью во время сушки очень важен для качественной сушки.

6. Пиломатериалы обычно оставляют на бирже пока содержание влаги не достигнет 20-25%.

7. Планировка биржи должна быть удобна для передвижения погрузчиков.

8. Количество бревен, которое может быть уложено в штабель, зависит от их длины и толщины.

9. На бирже бревна разгружают, укладывают в штабель, а затем направляют в лесопильный цех.

10. Проезды на бирже служат путями для транспортировки пиломатериалов, а также являются защитой против распространения огня.

2. Speak about:

1. The layout of a log sawmill yard.

2. The layout of a lumber yard.

Unit 6

Infinitive Constructions: Complex Subject Complex Object

Grammar:

Timber Drying Methods

1. Answer the questions:

1. Is green wood dry or wet?

2. Is it necessary to dry wood?

3. Why is it necessary to dry wood?

2. Read the text and try to understand it.

Growing trees are well known to contain a very great deal of water. A cubic foot of green oak may contain 22 lb, or over two gallons, of water and, as oak is a dense, impermeable wood it may take a very long time indeed for this water to dry out if wood is sawn into thick beams. Practically no drying at all will occur so long as the log remains with its bark on. In fact it will probably begin to decay before any appreciable drying takes place.

It has long been recognized that, except for a few purposes all timber should be seasoned (i.e. dried). The principal reasons for drying wood before it is used are:

1. to minimize the amount of shrinkage that will occur when it is used in a structure

2. to make it more resistant to fungal decay, staining and insect attack

3. to reduce its weight before handling and transport

4. to make it suitable to receive paints, varnishes and other finishes

5. to render it more absorbent of preservative fluids

6. to increase the strength and service life of wooden structures and articles.

Woods appear to vary greatly in the amount of moisture they can hold. This depends on the density of the wood, first of all. In a dense wood there is very little space to hold free water, while in a very light wood, such as balsa, there is so much space that a moisture content of several hundred per cent is possible.

The sapwood of a tree was found to have a much higher moisture content than has the heartwood. In some pines, for instance, the moisture content of the sapwood may be over 100 per cent while the heartwood contains 40 per cent or less. There is a great variation also between species. In Douglar fir the average moisture content of the tree when felled is only about 40 per cent. On the other hand, Western hemlock was found to have a very high moisture content even in the centre of the tree.

There are many ways of seasoning timber. But only two of them are in common use: air-drying and kiln-drying. Everybody knows the choice of seasoning method to depend on local conditions. For instance, if the climate is humid an accelerated kiln-drying method is likely to be cheaper than air-drying. However, for poles which need specially designed kilns air-drying may be the most economic method. But a combination of two methods is often desirable. Preliminary air-seasoning followed by a short period of kiln-seasoning is often practised.

Extensive technology aimed at reducing degrade and drying time has recently been introduced. These innovations include the use of vacuum pressures, microwaves, heat pumps. Four drying methods have come to use as ways to reduce drying losses, shorten drying times and reduce costs. They are: dehumidification drying, vacuum drying, drying in high-frequency field, radiation drying.

General understanding

Answer the questions:

1. Do the growing trees contain a great deal of water?

2. Do felled trees or timber contain much water? What do you think?

3. Is it an advantage or disadvantage for timber?

4. What are the main reasons for drying wood?

5. What does the amount of moisture depend on? Why?

6. Is there any difference in moisture content between sapwood and heartwood?

7. Do different species differ in moisture content either?

8. What are the most common methods of wood drying?

9. What does the choice of this method depend on?

10. What are the new methods of drying wood?