1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T L.61TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2004) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Optical fibre cable installation by floating technique ITU-T Recommendation L.61 ITU-T Rec. L.6
2、1 (07/2004) i ITU-T Recommendation L.61 Optical fibre cable installation by floating technique Summary This Recommendation describes the floating technique to install optical fibre cables in ducts. The floating process described in this Recommendation is always performed by means of water. It provid
3、es considerations on the equipment to be used, and gives advice on steps to be performed, and on procedures and precautions to be taken during the cable installation. Source ITU-T Recommendation L.61 was approved on 29 July 2004 by ITU-T Study Group 6 (2001-2004) under the ITU-T Recommendation A.8 p
4、rocedure. Keywords Air compressor, duct, floating, gradient pressure, water pump. ii ITU-T Rec. L.61 (07/2004) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T
5、) is a permanent organ of ITU. ITU-T is responsible 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 yea
6、rs, establishes the topics for study by the 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 nece
7、ssary standards are prepared on a collaborative 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. Compliance with this Recommendation is voluntary. Howeve
8、r, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability 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 equ
9、ivalents are used to express requirements. The use of such words does not suggest that compliance 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
10、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 of the date of approval of this Recommendation, ITU h
11、ad 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 to consult the TSB patent database. ITU 2004 All righ
12、ts reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. L.61 (07/2004) iii CONTENTS Page 1 Scope 1 2 References. 1 2.1 Normative references 1 2.2 Informative references 1 3 Definition 1 4 Abbreviations 1 5 Introduct
13、ion 2 6 Floating technique requirements. 2 7 Infrastructures. 3 7.1 Ducts. 3 7.2 Cable. 3 8 Equipment and settings in floating technique. 4 8.1 Water pump 4 8.2 Water tank 4 8.3 Cable pushing device (Caterpillar). 5 8.4 Cable-speed control 5 9 Preliminary phases 5 10 Installation issue . 5 10.1 Duct
14、 setting. 5 10.2 Cable setting . 6 11 Cable installation 6 Annex A Theory . 7 Appendix I Italian experience. 8 I.2 Bibliography. 10 ITU-T Rec. L.61 (07/2004) 1 ITU-T Recommendation L.61 Optical fibre cable installation by floating technique 1 Scope This Recommendation: gives a general description of
15、 the machine and operations needed in performing the installation of optical cables as defined in ITU-T Rec. L.10 inside ducts or conduits by means of floating technique; provides considerations on infrastructure, floating equipment and setting needed in using such a technique; gives advice on the p
16、reliminary steps that should be performed; gives advice on procedures and precautions to be considered during the cable installation. 2 References 2.1 Normative references The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute pr
17、ovisions 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 are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommenda
18、tions 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, as a stand-alone document, the status of a Recommendation. ITU-T Recommendation L.1 (1988), Construction, inst
19、allation and protection of telecommunication cables in public networks. ITU-T Recommendation L.10 (2002), Optical fibre cables for duct and tunnel application. ITU-T Recommendation L.35 (1998), Installation of optical fibre cables in the access network. ITU-T Recommendation L.57 (2003), Air-assisted
20、 installation of optical fibre cables. 2.2 Informative references ITU-T Handbook on “Construction, Installation, Jointing and Protection of optical fibre cables“. ISO 7611:1985, Gas chromatographic method on capillary columns. 3 Definition None. 4 Abbreviations This Recommendation uses the following
21、 abbreviations: EKE PolyEthylene Aramidic Yarn PolyEthylene EVE PolyEthylene Fibre Glass Yarn PolyEthylene HDPE High Density PolyEthylene 2 ITU-T Rec. L.61 (07/2004) NPx x bar value of Nominal Pressure 5 Introduction The floating technique is based on forcing along the cable route, by means of a pum
22、p, a suitable water flow. Moving water exerts a distributed action on the cable that pushes it forward at a speed in the range 30 40 m/min. There are no pulling forces applied at the front end of the cable: that extremity being completely free (with neither rope nor parachute attached). Moreover, th
23、e water thrust minimizes the friction effect generated between the cable and the duct during the installation process. Besides, because, with this technique, the applied forces on 1 m of cable element are around 0.10-0.15 N kg, the resultant forces applied on the cable are lower than those applied i
24、n the case of the use of pulling techniques, thus reducing the installation hazards. Additionally, if the fluid speed is such as to cause, on each cable element, a force greater than that aforesaid, then the presence of bends along the cable route becomes a less significant affecting factor compared
25、 with the pulling technique. Fluid speeds of 1 m/s are advisable for heavy optical cables (around 300 kg/km). Furthermore, since the density of the water is greater than that of the air, for a given type of cable (weight and diameter), a lower water pressure is requested with respect to the use of t
26、he Air-assisted technique. This also allows the laying of cables in ducts designed to withstand a working pressure (NP) of 6 bar (e.g., HDPE NP6 ducts) which would not be suitable in the case of the use of the Air-assisted technique. Cables are installed without virtual stress, leaving the cable rel
27、axed in the duct upon completion of the installation. Finally, water floating does not cause a significant increase of the duct temperature, providing another advantage over those systems that use gas as a laying element. 6 Floating technique requirements The choice of the floating technique depends
28、 mainly on: type of cable (diameter, weight, stiffness); duct diameter and duct characteristics vs. pressure; water availability; duct joints characteristics vs. inner pressure; shape of the route (number of bends, location of the bends, gradient). The maximum length of installed cable, as well as t
29、he maximum speed of installation, depend on the aforesaid factors and the equipment used according to the theory shown in Annex A. For uphill routes, the weight of the water pushing the cable towards the upper side should be taken into account. It is recommended increasing water pressure of about 1
30、bar per 10 m drop level. If the drop is relevant, the water pressure or increase may be incompatible with maximum pressure to be used with the duct and joints; in such a case, it is convenient to proceed with a downhill laying using a limited water quantity in order to get the allowed range. ITU-T R
31、ec. L.61 (07/2004) 3 7 Infrastructures 7.1 Ducts Material and thickness of the ducts and the watertight connectors fitting them should be suitable for the water pressure to be used. A reference value 6 bar is recommended. In order to prevent unforeseeable friction between duct and cable sheath, it i
32、s important to ensure that the duct is in a sound condition (it should keep its circular shape during installation) and as clean and clear as possible. Maximum duct diameter depends on the type of machine used. HDPE ducts with an external diameter of 40 50 mm, have allowed the installation of cable
33、lengths up to 6000 m. NOTE The use of HDPE ducts having a working pressure of less than NP6 degrees may be possible, but this has to be analysed considering the real application in the field (route length, cable type, route layout, duct inner diameter, duct characteristics vs. pressure). 7.2 Cable T
34、he maximum of length cable that can be installed is influenced by the stiffness of the cable. A very flexible cable (minimum curvature radius during installation less than 300 mm) can be floated without resistance as long as the bends along the route are greater than this value. A rigid cable may en
35、counter resistance during the laying in the duct if two consecutive bends are closely spaced, (e.g., 50 m). Consequently, friction between the cable sheath and the inner duct surface may become another important parameter in case of rigid cable structures. Such a parameter should be as low as possib
36、le: a typical value of the dynamic friction coefficient is 0.1. Moreover, according to Equation A.2, the lighter the cable is, the further it can be floated, but there is no linear relationship between the cable weight and the floating-in length. In order to limit the friction forces between cable a
37、nd duct, it is recommended to avoid two or more consecutive 90 bends spaced less than 20 m apart, otherwise, the cable stiffness could cause excessive friction corresponding to such bending points. To minimize the friction effect, the cable diameter shall not be bigger than 50% of the internal duct
38、diameter. In Table 1, the relationships among cable weights, type of ducts and maximum cable length installable for a linear route are shown. Table 1/L.61 Maximum cable length relative to cable and duct types Cable weight (kg/km) Duct types (HDPE ext 50 mm) Maximum floating length (m) 100 NP6 4000 1
39、00 NP10 6000 200 NP6 3000 200 NP10 4000 300 NP6 2000 300 NP10 3000 4 ITU-T Rec. L.61 (07/2004) 8 Equipment and settings in floating technique The most important parts of the system are: water pump; water tank; cable pushing device (caterpillar); water stream/cable coupling device. A communication sy
40、stem (usually a Radio link or mobile phone) shall be deployed for on site communications between the ends of the cable route. Figure 1 shows how the parts of the floating machine are assembled. caterpillarcoupling devicecablewater flowfrom pumpFigure 1/L.61 General assembly of the floating machine 8
41、.1 Water pump It is a motive station mounted on a truck used to generate a high-pressure water flow through the duct route. A pump generates a water flow that pushes the cable into the duct. By means of Equation A.4, it is possible to calculate the correlation between the speed of the water flow and
42、 its pressure. Maximum pressure to apply depends on the characteristics of the duct used (see ISO 7611). Practical pressure values are in the range of 4 10 bar. Pressure to be used has to be in accordance with the duct characteristics (see 7.1). 8.2 Water tank The capacity of the tank shall be able
43、to supply water for the maximum size of cable to be installed taking into account: duct inner diameter; duct length; cable diameter; cable installation speed; fluid speed. ITU-T Rec. L.61 (07/2004) 5 For example, in a typical installation of 6000 m, about 6000 litres of water are necessary to fill t
44、he duct before starting the cable installation, and another 2000 litres are necessary for its laying. A truck is then requested on which a water tank of about 8000 litres, assembled with the machinery controller and the cable reel, is loaded. A second tank may be used to recover the incoming water a
45、t the far end of the duct route. According to local rules, the water inside the duct should be recovered at the end of the cable installation (i.e., by means of an air compressor). 8.3 Cable pushing device (Caterpillar) The water flow and cable shall be directed inside a “flowing room“ in order to e
46、xert the dragging force on the cable. The Flowing Room System shall be used to couple both the cable and the high-pressure fluid flowing into the duct route. This system is positioned at the starting end of the cable laying and located as close as possible to the starting manhole in the duct route.
47、A caterpillar shall be used to trigger and regulate the cable installation speed. This is because the speed of cable installation, caused by the motive force of the water flow, is usually too high. The caterpillar makes it possible to stop the cable laying, restart it, and even to reverse the cable
48、laying. An example of the coupling mechanism process between the water stream and the cable is shown in Figure I.1. 8.4 Cable-speed control The cable speed shall be controlled by means of a mechanical device (caterpillar) that applies a force on the cable and pushes it into the duct at a controlled
49、speed. An example of a caterpillar is shown in Figure I.2. It shall be driven by a motor, provided with a manual and automatic run-stop device. A variable speed engine system shall also be used to match the speed of the cable reel to the required laying speed (the recommended laying speed is 40 m/min). 9 Preliminary phases For installations using the floating technique, all precautions considered in other installation techniques such as reels handling, cables, personal security, cable storage in splice point, etc.,
