1、 INTERNATIONAL TELECOMMUNICATION UNION L.46TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2000) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Protection of telecommunication cables and plant from biological attack ITU-T Recommendation L.46 (Fo
2、rmerly CCITT Recommendation) ITU-T L.46 (10/2000) i ITU-T Recommendation L.46 Protection of telecommunication cables and plant from biological attack Summary This Recommendation describes biological attacks and countermeasures for protection of telecommunication cables. It deals with the kinds of bi
3、ological attack, weakness of cables, features of damage, and considers alternative ways of protecting the plant including dependence on cable position. Source ITU-T Recommendation L.46 was prepared by ITU-T Study Group 6 (1997-2000) and approved by the World Telecommunication Standardization Assembl
4、y (Montreal, 27 September 6 October 2000). ii ITU-T L.46 (10/2000) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is resp
5、onsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the
6、ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborat
7、ive basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementat
8、ion of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As o
9、f the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged t
10、o consult the TSB patent database. Ge3 ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. ITU-T L.46 (10/2000) iii CONTENTS Page 1
11、 Scope. 1 2 The kinds of biological attacks . 1 3 Types of damage experienced. 1 3.1 Mammals (e.g. squirrels, rats, mice and gophers) 1 3.2 Insects . 1 3.2.1 Termites and ants. 1 3.2.2 Beetles, larvae and other insects 1 3.3 Birds 2 3.4 Micro-organisms. 2 4 Type of protection. 2 4.1 Positioning of p
12、lant in certain locations . 2 4.2 Elimination of the pest 2 4.3 Protection of telecom plant . 3 4.4 Cable construction 3 Appendix I 4 Appendix II 5 ITU-T L.46 (10/2000) 1 ITU-T Recommendation L.46 Protection of telecommunication cables and plant from biological attack 1 Scope There is evidence that
13、the outside of the plant can be damaged from biological attack. Some attacks are localized to particular environments which nurture certain types of infestation. Sometimes movement of the plant away from these areas is enough to avoid damage. More typically, the plant is shielded against attack by p
14、reventing penetration of pests some of which are listed in clause 2. 2 The kinds of biological attacks It is known that cable damage may be caused by: mammals, squirrels, mice, rats, moles, gophers and other rodents; birds like woodpeckers and cockatoos; insects such as termites, ants, beetles, wasp
15、s and caterpillars; micro-organisms like bacteria, fungus and/or moulds. 3 Types of damage experienced From an investigation of the damage sustained it is possible to determine the type of pest involved. Typical features of damage are given below. 3.1 Mammals (e.g. squirrels, rats, mice and gophers)
16、 Vertical chiselling of incisors on the edge of irregular holes is typical of the damage caused by rodents. Spherical or cylindrical holes with smooth walls are characteristic for the attack of moles. The animals are often found in the hole. 3.2 Insects 3.2.1 Termites and ants Irregular holes that m
17、ay extend over the whole circumference, looking as though the sheath has been peeled off, are typical of termites and ants. A mat appearance, to a surface that has been chewed over, is typical of termite gnawing, because they dig and lever upward with their short squat mandibles. Scratch marks and a
18、 transverse assault on the cable are characteristic of the ant, which has long, sharp mandibles and adopts a cutting action. In the early stages, the attack is characterized by local gatherings of numerous, small, individual holes. Ants and termites can give off an acidic secretion that is corrosive
19、 to lead. 3.2.2 Beetles, larvae and other insects Horizontal traces of mandibles of different shapes on the edges of the holes, are indications of attacks by insects and larvae. Circular bores are typical of larvae and beetles. Depending on the angle at which they penetrate the sheath, they may look
20、 circular or elongated with a width equal to the diameter of the bore. 2 ITU-T L.46 (10/2000) 3.3 Birds Irregular nibbles by beaks on the edge of and around irregular holes, are signs of attacks by birds. NOTE Earwigs, spiders, pupas and other animals, often invade junction boxes and other open spac
21、es. If the ventilation holes are big enough, even bird-nests, squirrel-nests and mice-nests can be found in the boxes. The debris these animals (in 3.1 to 3.3) produce from their excrements, also contribute to the breakdown of the insulation of connectors and terminal blocks. 3.4 Micro-organisms Det
22、erioration of the mechanical properties of cellulose fibres and elasticized polymers, is characteristic of attacks by fungi and bacteria. These attacks depend on the material and its manufacturing process. Local aeration corrosion cells can be produced by the attachment of barnacles, which are tight
23、 enough to exclude oxygen. These cells can be the result of bacterial metabolism in a polluted environment. 4 Type of protection 4.1 Positioning of plant in certain locations Attacks on telecom plants may be confined to certain areas where the conditions allow the pests to thrive. If it is possible
24、to re-route the plant away from these areas, instances of attack and plant damage can be avoided. Examples of particular environments and the type of biological attacker found in them are shown in Table 1. Table 1/L.46 Typical environment for pests Environment Pest Breeding places in rubber estates
25、Insects Willow, cascara, scrub oak areas and old trees Olive beetles Telecom plant in contact with plants (vegetable) cable drums-poles-wood debris-bamboo-roots Insects and larvae Dry rotting tree roots and wood debris Termites Above ground Up to 1.5 m in hard soil Deeper in soft soil Ants Polluted
26、soil and water creating anaerobic conditions Bacterial metabolism Overhead Squirrels and birds 4.2 Elimination of the pest Where it is not possible to re-site the plant one possible action could be to eliminate the pests such as insects and rodents using chemicals or poisons. It should be noted that
27、 some chemicals and poisons are useful as a countermeasure for biological attacks, but they sometimes can also be a danger to humans and cause environmental pollution. Therefore, very careful handling is required when using any chemical method to prevent biological attacks. Also, materials safety da
28、ta and other specifications should be referred to before they are ITU-T L.46 (10/2000) 3 used. Poisons and chemicals should be stored safely in accordance with the suppliers recommendations. Some chemicals are useful as a deterrent. These chemicals do not work as poisons but they repel the attacker.
29、 For example, some chemicals are sprayed on the cable surface and leave a special smell as a deterrent. 4.3 Protection of telecom plant Another option for protection of the plant is to shield it by the use of protective materials around the plant in order to prevent access. Examples of the way to pr
30、event access of the pests are given in Table 2. Table 2/L.46 External measures for protection against pests Action Pest Application of screens over ventilation opening Squirrels, rodents and birds Steel net over cable Squirrels Tightening of fittings in junction boxes, blocking with epoxy resin cast
31、ing in small boxes Ants, insects and beetles Compact into hard soil around cables and joints Ants and insects Cables in small diameter duct to prevent entry Rats and mice Galvanized iron guards around the cables as they emerge from the ground Rodents, ants and insects Chemical repellents sprayed on
32、telecom plant or spread around it Insects, spiders and wasps Covering/repair of damaged duct Rats 4.4 Cable construction Cables with sheaths of lead, polyethylene, polyvinylchloride, neoprene and other polymers are all susceptible to attacks. Examples of cable constructions that offer protections ar
33、e given in Table 3. Table 3/L.46 Cable construction for protection against pests Protection Pest Steel wire, fibreglass or aramid armouring Squirrels and rodents Steel sheath or steel tape laminate Birds Polyamide sheath Ants and termites Helical steel or brass tape Birds (woodpeckers) and termites
34、Helical steel (0.2 mm) lapping with bituminous compound flooding Contact with plants induce beetle and larvae attack Aluminium tape offers limited protection, especially thin foil (e.g. 0.1 mm) that is easy to penetrate. Therefore, the thickness of aluminium tape should be considered carefully. Cabl
35、es with steel armouring and/or dielectrical armouring such as fibreglass do not suffer any damage of this type as long as the armour is intact. Discontinuity in the armor leads to damage from beetles and larvae. Openings in the steel armour may have their origin in imperfect splicing and careless re
36、pairs, wrinkles and mechanical damage or by corrosion. 4 ITU-T L.46 (10/2000) Coatings of hessian, jute yarn or paper fibres impregnated with tar or bituminous compounds, give no protection. APPENDIX I Table I.1 shows the main biological attackers and countermeasures. Table I.1/L.46 The main biologi
37、cal attackers and countermeasures Caused by Attackers Position Troubles Countermeasures Mammals Rats and Mice Underground cables Duct cables Indoor cables Bite, Food, Cut Armouring net OLMA Sealing of duct Chemicals Mammals Moles Underground cables Cut Armouring net OLMA Mammals Squirrels Aerial Bit
38、e, Cut OLMA Birds Woodpeckers Other Birds Aerial Peck, Make hole Make nest Steel tape OLMA Insects Ants and Termites Underground Aerial Bite Bite Polyamide jacket Steel tape and Brass tape Air tightness of closures Insects Cicada Aerial Lay Eggs, Make hole Steel tape Micro organism Bacteria - - - OL
39、MA Over Lay Metallic Armouring ITU-T L.46 (10/2000) 5 APPENDIX II Experience for biological attacks is shown in this Appendix from Table II.1 to II.7. The information is gathered from Argentina, Italy, Japan, Spain, Ukraine and Brazil. The places of attacks are shown in Figure II.1. T0604880-00AaFFB
40、C D EfG HIJKcA Transmission Facilities, ex. FTM, DSUB Cables installed in tunnels, Metallic/OpticalC Underground ClosureD Duct CablesE Underground (Direct buried) CablesF Aerial ClosuresG Aerial Cables, Metallic/OpticalH Dropping CablesI Terminal Box, ex. Arrester BoxJ Indoor CablesK Equipmenta Tele
41、com facilitiesb Tunnelc Ductsd Manholef PoleFigure II.1/L.46 Illustration for places attacked by plants and animals Table II.1/L.46 Argentine experience Place (Figure II.1) Season Caused by Kind of cause Example of trouble When occurred CountermeasuresB All season Mammals Rats Bite None G All season
42、 Bacteria Others Peck None F All season Bacteria Others Make Nest None 6 ITU-T L.46 (10/2000) Table II.2/L.46 Italian experience Place (Figure II.1) Season Caused by Kind of cause Example of trouble When occurred Countermeasures D All season Mammals Rats Bite 1993 to 1995 None Table II.3/L.46 Indone
43、sian experience Place (Figure II.1) Season Caused by Kind of cause Example of trouble When occurred Countermeasures Jakarta All season Mammals Rats Bite, cut 1998 Making sealing of the cables ducts Jakarta All season Insect Ants Bite, make nest 1997 Chemicals, inserting wax Ujung Pandang All season
44、Insect Ants Bite, short circuit 1997 None Many places All season Mammals Mice Bite, cut, short circuit, make nest 1996-1998 None Ambon All season Birds Cockatoos Bite 1997-1998 None Table II.4/L.46 Japanese experience Place (Figure II.1) Season Caused by Kind of cause Example of trouble When occurre
45、d Countermeasures G All season Mammals, insects Rats, squirrels, mice, caterpillarsBite (Figures II.2 and II.3) 1996-1999 OLMA (Steel outer layer) (Figure II.4) Replacement with HS cable (Figure II.5) F Autumn insects Ants Bite 1998 Improvement of airtightness H Summer insects Cicada Lay eggs 1998 O
46、LMA (Steel outer layer) Replacement with HS metallic wire T0604890-00Figure II.2/L.46 Example of trouble by rats ITU-T L.46 (10/2000) 7 T0604900-00Figure II.3/L.46 Example of trouble by caterpillars T0604910-00Aerial CablePolyvinyl Chloride (PVC) SheetStainless SteelPVC Tapea) Configurationb) Illust
47、ration of how to use OLMAFigure II.4/L.46 OLMA 8 ITU-T L.46 (10/2000) T0604920-00Central strength element(Central rod)Optical fibre ribbonsStainless steelPE outer sheath(PE = Polythene)Figure II.5/L.46 Configuration of high strength (HS) cable Table II.5/L.46 Spanish experience Place (Figure II.1) S
48、eason Caused by Kind of cause Exampleof trouble When occurred CountermeasuresD All season Mammals Rats Cut 1996 None M All season Mammals Rats Cut 1996 None M All season Mammals Rats Cut 1997 None M All season Mammals Rats Cut 1997 Sealing Table II.6/L.46 Ukrainian experience Place (Figure II.1) Sea
49、son Caused by Kind of cause Examplof trouble When occurred CountermeasuresJ (3 events) All season Mammals Rats Bite 1998 Over lay metallic fray J (3 events) All season Mammals Rats Food, Bite 1998 OLMA D, J All season Mammals Rats Bite, Cut, Scratch 1998 Armouring Net, chemicals D All season Mammals Rats Bite 1996 Over lay D (20 event) All season Mammals Rats Bite 1997 Over lay D All season Mammals Rats Bite 1998 Making sealing of duct D (2 event) All season Mammals Rats Cut, Food, Bite 1998 Over l
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1