1、 International Telecommunication Union ITU-T L.77TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2008) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Installation of optical fibre cables inside sewer ducts ITU-T Recommendation L.77 ITU-T Rec. L.
2、77 (05/2008) i ITU-T Recommendation L.77 Installation of optical fibre cables inside sewer ducts Summary ITU-T Recommendation L.77 describes methods to install optical cables inside sewer ducts, which applies to both the cable installation and the pre-installation of an infrastructure, if requested.
3、 This Recommendation covers both man- and non-man-accessible sewer ducts. This Recommendation is not intended to address all of the safety concerns, if any, associated with its use. Therefore, it shall be the responsibility of the user of this Recommendation to establish appropriate health and safet
4、y practices and determine the applicability of regulatory limitations, if any, prior to its use. Source ITU-T Recommendation L.77 was approved on 29 May 2008 by ITU-T Study Group 6 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. L.77 (05/2008) FOREWORD The International Telec
5、ommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and ta
6、riff 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 ITU-T study groups which, in turn, produce Recom
7、mendations 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 collaborative basis with ISO and IEC. NOTE In this Recomme
8、ndation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interoperabi
9、lity or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that comp
10、liance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validit
11、y or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be require
12、d to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2008 All rights reserved. No part of this publication may be reproduced,
13、 by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. L.77 (05/2008) iii CONTENTS Page 1 Introduction 1 2 References. 1 3 Installation of infrastructure and/or optical fibre cables inside sewer ducts 2 3.1 Sewer assessment . 2 3.2 Installation in non-man-accessible sewers
14、 . 2 3.3 Installation in man-accessible sewers. 3 3.4 Installation of special armoured optical cable into the sewer ducts . 4 4 Application of over-length storage boxes and sewer splice closures . 5 5 Connection between sewer manholes and telecommunication manholes 5 5.1 Connections between sewer op
15、tical cables and traditional cables . 5 6 Guidelines for the selection of the most appropriate installation method 6 7 Maintenance effects 6 7.1 Sewer integrity 6 7.2 Pressure washing and finishing brush 7 7.3 Root saws 7 7.4 Slip lining . 7 8 General guidelines for the installation of self-supporti
16、ng optical cable into the sewer ducts . 7 9 Safety 9 Appendix I Italian experience. 10 I.1 General design of the optical cable 10 I.2 Description of optical cable structure. 10 I.3 Main performance of the optical cable. 10 I.4 Others characteristics of the optical cable 11 Appendix II Chinese experi
17、ence. 12 II.1 General design of the optical cable 12 II.2 Description of optical cable structure. 12 II.3 Main performance of the optical cable. 12 II.4 Other characteristics of the optical cable 13 Bibliography. 14 ITU-T Rec. L.77 (05/2008) 1 ITU-T Recommendation L.77 Installation of optical fibre
18、cables inside sewer ducts 1 Introduction The installation of optical cables inside sewer ducts is basically a trenchless technique. Optical cable installation in sewer ducts presents many advantages compared with traditional trench installation techniques, such as: less time for cable laying, not li
19、mited by weather conditions, increased protection of cable against damage, no traffic disruption, no noise pollution, no excavation, no damage to road surfaces and underground installations, no heavy equipment, no inconvenience to businesses or to citizens. In general, there are two categories of se
20、wers: man-accessible and non-man-accessible sewers. The definition of whether a sewer is man-accessible or not depends not only on national regulations, but also on the individual regulations of different sewer network operators. Usually, non-man-accessible sewers have diameters between 200 mm and 7
21、00 mm. Installation in non-man-accessible sewers is carried out with the help of robots. In man-accessible sewers, both robot-assisted and manual installation of cables is feasible. Basically, there are three different methods to install optical cables into sewer ducts: a) Special armoured optical c
22、ables, designed to be directly installed at the bottom of the sewers; b) Self-supporting optical cables, designed to be directly suspended at the top part of sewers; c) Traditional optical cables or micro-cables, designed to be installed in protective ducts which have to be installed before the cabl
23、e installation. NOTE 1 The most important optical cable structures and related performances suitable for these kinds of installation techniques are described in ITU-T L.78. NOTE 2 The sewer optical cables and/or related infrastructure should be designed and manufactured for an expected operating lif
24、etime of at least 15 years. It should be possible to install or remove the cable to/from the sewer throughout the operation lifetime. The materials in the sewer optical cable and/or the related infrastructure shall not present a health hazard within its intended use. 2 References The following ITU-T
25、 Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation
26、are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, a
27、s a stand-alone document, the status of a Recommendation. ITU-T L.1 ITU-T Recommendation L.1 (1988), Construction, installation and protection of telecommunication cables in public networks. ITU-T L.10 ITU-T Recommendation L.10 (2002), Optical fibre cables for duct and tunnel application. ITU-T L.12
28、 ITU-T Recommendation L.12 (2000), Optical fibre joints. ITU-T L.35 ITU-T Recommendation L.35 (1998), Installation of optical fibre cables in the access network. 2 ITU-T Rec. L.77 (05/2008) ITU-T L.78 ITU-T Recommendation L.78 (2008), Optical cable construction for sewer applications. 3 Installation
29、 of infrastructure and/or optical fibre cables inside sewer ducts 3.1 Sewer assessment Exact information about the structural condition of the sewer networks in which cable systems are to be installed is to be considered as a prerequisite. It must be clarified whether the pipes are suitable with res
30、pect to their structural/operating condition, capable of being used for the installation of an optical cable. Furthermore, in the case of non-man-accessible sections, it must be determined whether these are suitable for installation by a robot. Thus, for example, significant structural changes in th
31、e sewers (collapse) or promontory pipe junctions can hinder the use of robots or even make their use impossible if other remedial measures are unable to solve the problem. The static bearing capacity of the sewers and their suitability for rehabilitation measures must be estimated using the results
32、of the assessment. Equally important to the assessment of the static bearing capacity, the hydraulics must be checked with respect to the reduction of the section caused by installation of the cable. This will determine whether one or, if necessary, even several cables can be installed in a pipe or
33、sewer. In planning the cable routes, the experience of the sewer network operator with respect to loading and strategic planning for the future, additional discharges into the sewer must be taken into account. The operation of the sewer networks must not be affected by the installation of cables. Th
34、e cables must adhere as much as possible to the pipe ceiling. The technology used must also ensure that the sewer ducts are not damaged during the installation or the operation of the cable network. In the area of the manholes, the cables must be laid so that solids cannot be caught on them and in s
35、uch a way as to ensure safe accessibility to the manhole. A suitable grounding system is documented to avoid the formation of high induced voltage and sparking, which is absolutely not acceptable in locations with explosion hazards, such as the sewer systems. At the entry and exit of sewer pipes, a
36、connecting point for equipotential bonding between all the metallic parts of the infrastructure and the cables must be provided, measured and documented. 3.2 Installation in non-man-accessible sewers Installation in non-man-accessible sewers is made by robots and shall be damage-free when using all
37、types of pipe material (vitrified clay, plastics, concrete, etc.). Anchoring installation methods in non-man-accessible sewers are not recommended as the sewer pipe wall thickness is weakened by drilled holes and might break due to the heavy load or pipe sagging. Later alterations and extensions of
38、manhole installations and/or of the telecommunications network shall be possible. The optical cable infrastructure consists of protective conduits fixed, by using a robot, to the sewer duct by special clamps equipped with clips. All the materials used for the infrastructure in the sewer pipes must b
39、e of stainless steel type (V4A, CrNiMo-steel) to ensure the mechanical protection in the sewer environment and the protection against rodents for the optical cable. The clamps are adjustable 360 ring straps. Depending on the requirements of the communication network, clamps for sewer pipes with a no
40、minal diameter of 300 mm and above can be equipped with up to nine clips, so that up to nine protective conduits can be mounted. Sewer pipes with a nominal diameter of 200 mm or 250 mm can be equipped with a maximum of three clips. Protective conduits shall be corrugated tubes. The corrugated steel
41、tubes are available with an outer diameter of 11.5 mm or 15.5 mm in order to cause only a negligible reduction of cross section. Sewer rehabilitation work can still be carried out after the installation. ITU-T Rec. L.77 (05/2008) 3 Flexible cable trays can be used to guide and protect the optical ca
42、bles in sewer manholes if the protective conduits cannot pass the manhole or if an over-length storage box or a cable closure has to be installed in the manhole. All the parts shall be designed to guarantee the minimum allowed cable bending radius on the entire network installed into the sewers. For
43、 the application in sewer systems, the optical cables should have modified polyethylene sheaths. 3.2.1 Visual inspection Visual inspection of the sewer by the installation robot is mandatory in order to exactly evaluate the status and geometry of sewer sections, and to confirm next-step installation
44、 possibility. When passing through the sewer, the exact location of pipe joints and laterals are recorded, allowing the determination and documentation of the optimum position of the clamps in the sewer pipe. 3.2.2 Installation of the clamps First of all, the robot installs the clamps, which are mou
45、nted at a typical distance of 1.5-1.8 m inside the sewer ducts. In order to install a clamp, the spring box on the clamp is unlocked, so that the clip ring is expanded against the duct wall and tightly fixed to the inside sewer wall without drilling, cutting or screwing. 3.2.3 Laying and fixation of
46、 the protective conduits In order to install the conduits, they are pulled into the sewer pipes, and then the robot presses them into the clips of the already installed clamps. They are laid straight like a bar directly onto the inside sewer duct wall. 3.2.4 Mounting of the manhole parts The mountin
47、g of the manhole parts is done manually. 3.2.5 Installation of the optical cable The optical cables are blown into the conduits. The necessary equipment and procedures are similar to the standard installation of optical cables into micro ducts. It is recommended that the maximum diameter of the cabl
48、e be 70-80% of the corrugated steel tube diameter. For example, for the installation in a 11.5-mm corrugated steel tube, the maximum diameter of the cable is 9.2 mm; for a 15.5-mm tube, the maximum cable diameter is 11.5 mm. 3.3 Installation in man-accessible sewers The optical cable infrastructure
49、consists of protective conduits fixed to the sewer wall by special clip holders equipped with clips, in which protective conduits can be fitted. All the materials used for the infrastructure in the sewer pipes must be of stainless steel type (V4A, CrNiMo-steel) to ensure mechanical protection in the sewer environment and protection against rodents for the optical cable. The clip holders are straps fixed by the operators with expansion bolts. The wall thickness in sewers with a nominal diameter of 800 mm and above allows for the holes drilled to accommodate expansion bo
