ITU-T HDBK PWP-1974 Preservation of Wooden Poles Carrying Overhead Telecommunication Lines《高架通信线路木杆的保护》.pdf

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1、THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE (C.C.I.T.T.) PRESERVATION OF WOODEN POLES CARRYING OVERHEAD TELECOMMUNICATION LINES Published by THE INTERNATIONAL TELECOMMUNICATIONS UNION GENEVA - 1974 a 8$11 4862573 0678662 705 111 THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTA

2、TIVE COMMITTEE (C .C .I.T.T.) PRESERVATION OF WOODEN POLES CARRYING OVERHEAD TELECOMMUNICATION LINES Published by THE INTERNATIONAL TELECOMMUNICATIONS UNION GENEVA - 1974 O 6 4b25L Ob8bb3 b4L E FOREWORD A first edition of this booklet was prepared during 1956-1958 with a view to drawing attention to

3、 the importance of preserving the wooden poles carrying overhead telecommunication lines, and to provide Admi- nistrations developing their networks with some information on impregnation processes. At the IVth C.C.I.T.T. Plenary Assembly (Mar del Plata, 1968) it was decided that a complete revision

4、of the booklet was required and this second edition is the result of work done mainly by the Argentine Administration, in association with C.C.I.T.T. Study Group VI and including also information supplied by the Administrations of Australia, Austria, Chili, France, Federal Republic of Germany, Italy

5、. Norway, Switzerland and by the United Kingdom Post Ofice. In presenting their first draft of the revised text, the Argentine Administration made the following com- ment s: “No work of this kind can claim to be exhaustive. We have tried to produce a coordinated text containing the basic concepts ma

6、king it as clearly understandable as possible and excluding contro- versial matters. as is desirable in dealing with such specialized subjects as this. Chapter II can probably be extended in later editions to include additional information from other Administrations and provision should be made for

7、bringing the material up to date, say, every five years. The same observation applies to Annexes I, 2 and 3 which are intended to serve simply as background information. * Previous page is blank. e 4862591 0678664 588 R TABLE OF CONTENTS THE PRESERVATION OF WOODEN POLES CARRYING OVERHEAD TELECOMMUNI

8、CATION LINES CHAPTER 1 . General considerations Page 1.1 Purpose of this publication 1.2.2 Species used for poles 1.2 Basic concepts 1.2.1 Regional character of preservation problems . 1.2.3 Destructive agents 1.2.4 Climatic conditions . I . 2.5 Economic conditions I . 2.6 Customers of the wood-pres

9、erving industry 1.2.7 Statistics and controls . CHAPTER II . Economic advantages ofpreservation 2.1 Length of life of impregnated poles 2.2 Practices and experience in various countries 2.3 Additional remarks extending the data in point 2.2 2.3.1 Argentina 2.3.2 Australia . 2.3.3 Austria 2.3.4 Franc

10、e 2.3.5 Italy CHAPTER 111 . Preserving substances 3.1 Types of preservative and general remarks 3.2 Oily preservatives 3.2.1 Creosotes 3.2.2 Reinforced creosote 3.3 Solvent-type preservatives . 3.3.1 Pentachlorophenol 3.3.2 Naphthalene chlorates . 3.4 Single water-borne substances . 3.4.1 Copper sul

11、phate . 3.4.2 Mercuric chloride 3.5 Combinations of water-borne substances i 7 7 8 8 8 9 10 10 II 11 11 II 12 12 12 12 17 18 18 18 18 18 19 19 19 19 19 CHAPTER iv . Preservation processes 4.1 General 21 4.2 Summary of preservation processes . 21 4.3.1 Vacuum-pressure processes . 4.3.3 Sap-displaceme

12、nt processes 4.3.3. I Boucherie process . 21 21 4.3 Methods of treatment 4.3.2 Thermal process 22 . 22 . 22 4.3.3.2 Geweke process 23 23 . 4.3.3.3 Pressure-tank suction process Previous page is blank . 6 TABLE OF CONTENTS Page 4.4 Diffusion processes 23 4.4.1 Single or double diffusion processes by

13、immersion . 23 4.4.2 Paste diffusion processes 23 ANNEX 1. Chief water-borne copper-mixture preservatives used to impregnate poles 25 ANNEX 2. Organizations carrying out research and tests on pole preservation 26 ANNEX 3. Bibliography . 27 48b25L Ob7bbb 350 i 7 THE PRESERVATION OF WOODEN POLES CARRY

14、ING OVERHEAD TELECOMMUNICATION LINES CHAPTER I GENERAL CONSIDERATIONS 1.1 Purpose of this publication Since the problems of preserving wood against biological agents depend on the region and are of interest to other enterprises besides telegraph and telephone companies, they have to be studied mainl

15、y in a regional context by joint groups of technicians, producers and users of poles. It is not the intention of the C.C.I.T.T. to usurp the role of such groups and the aims of this booklet are therefore as follows: - to draw the attention of telecommunication Administrations to the economic advanta

16、ges of giving the poles they use preservative treatment; - to describe, for general information, the considerations to be borne in mind in applying this treat- ment and the planning and organization required; - to provide a reference work-which would otherwise be difficult to assemble-for judging th

17、e behaviour and efficacy of the various treatments, according to the different species, requirements, destructive biological agents and climates; - to indicate to telecommunication Administrations the regional research institutes best able to advise them and to provide a list of selected publication

18、s for more detailed study. This publication deals with wooden poles only. Such poles are in widespread use for carrying overhead lines (open-wire and cable) being cheap, light and of high mechanical strength. The poles should be inspected at regular intervals after they are erected and as a safety m

19、easure before they are climbed. The soundness of the poles can be tested by various methods, ranging from visual inspection to the use of electronics devices. An experienced worker can generally assess the state of a pole by tapping it with a hammer and listening to the sound emitted. The most vulne

20、rable part of the pole lies between points about 30 cm above and 30 cm below the ground level. The present publication does not deal with other means of prolonging the life of poles such as precautions in siting them or the use of waterproof substances to protect the foot of the pole from damp. 1.2

21、Basic concepts 1.2.1 Regional character of preservation problems The chief function of a wood preservative is to protect the pole from attacks by different biological organisms. The conditions in which the pole is to be used may imply a greater risk from a particular organism. However, there may als

22、o be a combined effect, the presence of one organism either helping or being necessary for another to get a hold, each seemingly thriving from the presence of the other. On the other hand. the des- tructive process may quite simply be due to the action of different biological agents acting independe

23、ntly in time and place. Regions often have their own peculiarities which need to be studied, especially when consideriiig the introduction of new preservatives or techniques developed in other parts of the world to meet local require- I 4862571 0678667 297 I 8 CHAPTER U1.2.4 ments there. Preservatio

24、n requirements in a tropical region, for example, obviously cannot be equated with those of a temperate zone. it is evidently of importance to treat the problem in a regional context. This is the basic approach designed to prevent the automatic transfer of techniques and standards to an environment

25、for which they are not at all suited, or to which they need to be adapted. The whole purpose of treatment is to modify the relationship between the wood and the destructive agent, which is governed by very complex factors. The cli- mate, the preservative, the mode of treatment, forestry practices an

26、d local customs together create a set of conditions within a given country such that complete techniques cannot be transferred from one area to another. Economic factors should also be considered. 1.2.2 Species used for poles Only timber that has sufficient natural durability to make its use worth w

27、hile, or which lends itself to preservative treatment, is used for poles. It is common mistake to assume that because the wood of a particular species is hard or very dense, it must. be durable. In fact, not many woods in the world are suitable for poles and have sufficient durability without the ad

28、dition of a preservative. Natural durability depends on the quantity of natural preservative sub- stances present in the wood, particularly tannin and phenolic compounds. Particular mention may be made of Western red cedar (Thuya plicatu) among the conifers and the following species among broad-leav

29、ed trees : the chestnut (Castanea spp.), ironbark (Eucalyptus siderophloia, E. siderozylon, E. crebra), red quebracho (Schinopsis spp.), white oaks (Quercus spp.), urunday and urundel (Astronium spp.) and teak (Tectona grandis). There is no point in mentioning the different types of wood used for im

30、pregnated poles since they vary according to the region or even according to the country. However, it may be mentioned that in the Northern Hemisphere conifers are normally used, especially those of the Pinus genus in America and of the Abies, Pinus, Picea, Pseudotsuga and Larix genera in Europe, wh

31、ile various species of eucalyptus are often used in the Southern Hemisphere. I .2.3 Destructive agents Deterioration and destruction of wood are chiefly due to biological agents. In the case of poles, the main organisms responsible for damage are xylophagous fungi and xylophagous and lignicolous ins

32、ects (chiefly coleoptera and isoptera; this latter group includes termites) which feed on them or destroy them by boring. The distribution and importance of these agents depend, generally speaking, on the local environment. Consequently, apart from a few cosmopolitan types, the species of fungi, col

33、eoptera and termites differ accor- ding to the place. This means that the efficacy of the preservation treatment depends largely on a knowledge of the destructive agents of economic importance at work in the region where the poles are erected. Since deterioration is faster in wet regions and may be

34、slower in dry ones, a given preserving treatment is generally less effective in wet regions. 1.2.4 Climatic conditions From the time a pole is erected it is exposed not only to the action of biological agents but also to the weather: it may be subjected to hot sun, rain and humidity according to the

35、 local climate. These factors may impair the effect of the preserving agent by reducing the time during which it remains in the wood. Furthermore, climatic conditions affect physical behaviour of poles, particularly as regards splitting of the wood. In the species in which preservation depends exclu

36、sively on the treatment of a narrow band of sap-wood, as with species of the eucalyptus genus, for example, the cracking may extend beyond that area, facilitating the action of organisms in the untreated heart-wood. In English, the broad-leaved species are also distinguished from the conifers by cal

37、ling them “hardwoods“ and “softwoods“ respectively. These two terms have no mechanical significance, the range of mechanical properties in each group being very broad. B1 4862593 Ob78bb8 323 II CHAPTER 1/1.2.5 9 When choosing the impregnation process to be applied and the composition and quantity of

38、 the pre- servative to be used, both the climate and the risk of biological attack must be taken into account. i .2.5 Economic conditions A preserved pole is a piece of timber that has absorbed in the course of treatment a certain amount of a substance which will prevent or retard biological attacks

39、 on the ligneous tissue. Assuming that the mechani- cal strength requirement is fully satisfied, any significant differences in effectiveness are to be attributed to two basic variables-retention and penetration. The retention is the amount of active substance expressed in pounds or kilogrammes inco

40、rporated in one cubic foot or one cubic metre of wood respectively, while the penetration is the depth to which the wood is permeated. Nevertheless, when the preservative is dissolved in a liquid, as is the case for instance with the water- borne substances, and when as a result the solution absorbe

41、d by the timber contains only the proportion of preservative components determined by the concentration of the solution, the degree of concentration must be taken into account, and it must be an essential condition that the quantity of liquid absorbed is the maximum compatible with the permeability

42、of the timber (refusal treatment). This is in accordance with the way in which research institutes test the effectiveness of their products. They make solutions of different strengths which are used totally to impregnate samples of sap-wood and these are first tested for resistance to leaching, and

43、then exposed to attack by destructive agents that may be of importance in the region concerned. From these results the requisite quantities in kg per cubic metre can be determined, these are then mul- tiplied by a given factor corresponding to the maximum amount of solution absorbed normally by the

44、sap-wood of the species in given humidity conditions. Furthermore, experience shows that in preservation treatments, at the end of the process the absorption of a solution and the retention of a product in the impreg- nated timber differs from one pole to another even with the same species, and rega

45、rdless of the method used. These differences in similar types of wood are due to the proportion of sap-wood, for example, and to the differential distribution of the substances in the preservative through the ligneous tissue. As these well-known phenomena cannot be evaluated precisely in advance it

46、is necessary to inject the maximum volume of solution at a concentration corresponding to the desired protection or retention. It is important to fix a retention value or, when applicable, the degree of concentration for each pre- servative depending on the biological action expected in a given regi

47、on and on the planned service life of the overhead route. The relationship between the retention and the effectiveness in years of service also depends on the preservation method chosen. Not all types of treatment give results that meet the specified requirements. Industrial processing is the most r

48、eliable as regards homogeneity, which is a desirable characteristic of the preserving operation. This calls for extensive equipment and investment, especially in the case of vacuum-pressure processes which are advisable when large quantities of correctly impregnated poles are required. In areas of d

49、ificult access, transporting the poles before and after impregnation may be impossible or account for a large part of the total costs, or there may be other technical and economic factors, often varying from one country to another or from one area to another within the same country. In such cases, if there are local forestry resources, it may be wise to choose a method enabling the poles to be preserved on the spot (sap replacement and diffusion treatment), and the Boucherie process seems to be particularly indicated as it pro- vides a large number of poles with high-quality treatme