1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T L.28TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2002) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT External additional protection for marinized terrestrial cables ITU-T Recommendation L.28 ITU-T
2、 Rec. L.28 (10/2002) i ITU-T Recommendation L.28 External additional protection for marinized terrestrial cables Summary This Recommendation describes the external protection devices which can be utilized during/after the laying or during/after the reparation of Marinized Terrestrial Cables (MTC). S
3、ource ITU-T Recommendation L.28 was prepared by ITU-T Study Group 6 (2001-2004) and approved under the WTSA Resolution 1 procedure on 29 October 2002. ii ITU-T Rec. L.28 (10/2002) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of teleco
4、mmunications. The ITU Telecommunication Standardization Sector (ITU-T) 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 Telecomm
5、unication Standardization Assembly (WTSA), which meets every four years, 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
6、 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 Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized opera
7、ting agency. 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, validity or applicability of claimed Intellectual P
8、roperty 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 required to implement this Recommendation. However,
9、 implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2003 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T
10、 Rec. L.28 (10/2002) iii CONTENTS Page 1 Introduction 1 2 References. 1 3 Burial and external protection devices . 1 Appendix I Examples of external cable protection. 3 Appendix II Bibliography . 5 ITU-T Rec. L.28 (10/2002) 1 ITU-T Recommendation L.28 External additional protection for marinized ter
11、restrial cables 1 Introduction A marinized terrestrial cable is an underwater optical fibre cable, based on a conventional multi-fibre terrestrial cable core construction and protected to withstand the marine environment. It is designed for unrepeatered applications, that is, without underwater line
12、 amplifiers, hence without the need of power feeding for submerged equipment and has been tested for use in non-aggressive shallow waters, with a varying repair capability. The difference with respect to a repeaterless submarine cable can be found in the definition given in ITU-T Rec. G.972. Cables
13、are designed with a predicted lifetime, taking into account either cable replacement or a certain number of repairs. For shallow-water cables, the probability of failures is higher than for deep-water application due to environmental phenomena (for example, sea-wave motion, underwater earthquakes an
14、d landslides, etc.) and human activities affecting the seabed (for example, fishing, laying and maintenance of other services and cables). In addition to the various armour usually adopted for the cable construction for example Rocky Armour (RA), steel wire armouring such as single armour (SA) or do
15、uble armour (DA), additional external protections could be adopted if needed. Such protections can be applied both approaching the coast in shallow water and on shore in the portion between the water edge and the Beach Joint, or along the cable route where external factors or seabed features could d
16、amage the cables. 2 References The following ITU-T 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
17、subject to revision; users of this Recommendation 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 docum
18、ent within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T Recommendation G.972 (2000), Definition of terms relevant to optical fibre submarine cable systems. ITU-T Recommendation G.976 (2000), Test methods applicable to optical fibre submarine
19、cable systems. 3 Burial and external protection devices Burial and external protection devices have to be combined in the shore approach and in shallow water in relationship to the seabed feature and human activities. Cable external protection devices and or trenching have to be utilized in areas wh
20、ere some fishing activities or vessel/ship anchoring, etc., could damage the cable itself in spite of the protection already existing in the cable structure construction. Therefore, where it is necessary to meet the predicted lifetime and the cable reliability requirements during or after the instal
21、lation/reparation of cable, the following protection devices are adopted: 3.1) In the shore portion (generally defined between the Beach Joint and the 5 m water depth) 2 ITU-T Rec. L.28 (10/2002) The cable should be protected with cast iron shells and buried at least 2-3 m. In the beach up to the wa
22、ter edge, the cable, where necessary, should also be covered with concrete flat bricks and moored by chains to an anchor block or directly to the beach manhole if present. If rocky bottom is present in the very shallow water portion, the cable should be anchored to the rock with crossed chains by us
23、ing set pins. In the case of sand, concrete bags should also be used as extra protection to cover the cable and avoid grabbing or dragging along this section. 3.2) In the shallow water portion (generally defined between 5 m and 30-40 m water depth) The burial depth, trenching method and external pro
24、tection devices depend on seabed features and human activities in the interested marine area. 3.2.1) In case of soft bottom (for example, loose sand) The cable should be buried at least 1 m (for example, by divers or by using jetting methods). In deeper water, along the cable route where possible or
25、 convenient, the burial should be performed using plowing or jetting machinery. Usually, due to its softness and loosing, the sand will naturally backfill the trench. 3.2.2) In case of hard bottom If the hardness of the soil (for example, rocks, biotherm) does not allow burial, the cable should be p
26、rotected and secured (for example, by means of cast-iron shells duly secured to the soil in order to avoid movements due to sea-wave motion). In areas where these shells are liable to be damaged, the articulated pipe formed by them should be protected by concrete-gravel bags clamped to each other. W
27、here several cables are foreseen to be concentrated in a rocky shore approach, more additional protection is needed to prevent damage between the cables due to the environment (e.g., friction effects, etc). This protection (commonly known as tube) is in the form of helically wound steel types/wires
28、on each cable at the time of installation. The protection is needed for up to 100 m from the waters edge and in water depths up to 5 m. The pipes can be fixed and protected by mattresses and backfilled using same original rocks. A proper combination of the above-mentioned methods should be applied w
29、hen the seabed features change along this section. Appendix I are shows some examples of possible external cable protection devices. 3.3) Other cable or marine service crossing When a crossing is foreseen, the cable route and the cable protection, as well as the installation method, have to be deter
30、mined by the parties concerned (owners of the plant). As a general rule, the crossings between cables shall be performed as near to a right angle (90 degrees) as possible. It is highly recommended that crossing angles minor of 45 degrees be avoided in order to ensure properly operational and mainten
31、ance activities. Moreover, cable crossing types shall be chosen to avoid as much as possible the risk of abrasion. For example, if an armoured cable has to be installed over an existing Light Weight (LW) cable, then special coverings shall be applied to armoured cables or special crossing methods ha
32、ve to be implemented where this situation is deemed unavoidable; on the contrary, if a LW cable has to be installed over an existing armoured cable, then it is advisable that a short length of armoured cable be adopted in correspondence with the crossing point. In the case of a crossing of an alread
33、y installed cable by gas pipelines, oil pipelines, power cables, etc., the cable should be suitably protected with devices (for example, mattresses or rock dumping) able to prevent any damage during the laying, maintenance and recovery operations of such plants. With this in mind, action should be c
34、oordinated between those responsible for the two services. ITU-T Rec. L.28 (10/2002) 3 Similar protection devices should be adopted when a cable has to cross an already existing pipeline if: the pipeline carries warm substances (for example, oil ducts in the proximity of the wells), the temperature
35、of which could modify or damage the external sheath or the tar protecting the steel wire armouring of the cable in proximity of the contact point between cable and pipeline; the contact between pipeline and cable could lead to the generation of corrosion due to galvanic currents if cathode protectio
36、n is not used; mechanical friction between pipeline and cable, due to the water motion, could damage the cable. Appendix I Examples of external cable protection L.028_F01Sediment layer Bags Cast-iron shells CableSediment layerCableBagsCast-iron shellsSea bottomRock Rock Figure I.1/L.28 Cable protect
37、ed with cast-iron shells and sand cement bags 4 ITU-T Rec. L.28 (10/2002) L.028_F02Cable free spanBagsSea bottomBagsSea bottomCableSandRock Rock SandFigure I.2/L.28 Protection performed by positioning sand-cement bags under, laterally and above the cable L.028_T03Figure I.3/L.28 Photo of an example
38、of cable free span reduced using concrete bags ITU-T Rec. L.28 (10/2002) 5 L.028_T04Figure I.4/L.28 Photo of an example of external cable protection using cast-iron shells and additional sand concrete bags Appendix II Bibliography ITU-T Handbook (2001), Marinized Terrestrial Cables. Printed in Switz
39、erland Geneva, 2003 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series B Means of expression: definitions, symbols, classification Series C General telecommunication statistics Series D General tariff principles Series E Overall network operation, telephone service, se
40、rvice operation and human factors Series F Non-telephone telecommunication services Series G Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I Integrated services digital network Series J Cable networks and transmission of television, s
41、ound programme and other multimedia signals Series K Protection against interference Series L Construction, installation and protection of cables and other elements of outside plant Series M TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile an
42、d leased circuits Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipment Series P Telephone transmission quality, telephone installations, local line networks Series Q Switching and signalling Series R Telegraph transmi
43、ssion Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks and open system communications Series Y Global information infrastructure and Internet protocol aspects Series Z Languages and general software aspects for telecommunication systems *23098*
