江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
Challenges in Completing an International Telecom Cable System Sea Trial
by Dr Jerry Brown, Xu Rendong, Sun Guilin, Sun Xiaohua, Hao Changji, Xu Guoxiang, Jiang Yin, Zhang Chao
Hengtong Marine Cable Systems
1. Introduction:
China has a rapidly developing submarine cable system manufacturing industry which operates in a healthy competitive manner. Subsea cables can fall into several different system product streams including relatively standard products for long haul telecoms projects (the subject of this paper) and customised products for the Oil & Gas, Scientific Observation Systems, Defence applications and HV subsea cables. While much of the Telecoms product has been sold in the domestic market, Hengtong Marine has broken into the International Market by addressing client concerns over quality and now has a track record for deployed overseas systems. This has been achieved in part by completing an offshore cable system sea trial, which is a requirement of the cable system qualification to ITU-T G-976 & ITU-T G.972 standards. The requirement for a sea trial is a barrier which every cable system producer has to address to achieve international sales. Hengtong Marine is moving forward to promote and improve the image of “Global Quality from China”.
2. Different Products, Different Standards:
At Hengtong Marine Cable Systems, our product portfolio covers the following –
2.1 Subsea Telecoms Systems. These use relatively standard designs of long haul optical telecom cables (both repeatered & un-repeatered). These products generally cover 5 or 6 cable types (Rock Armour, Double Armour, Single Armour, Single Armour Light, Lightweight Protected & Lightweight Cables) which are manufactured and qualified to ITU-T G-976 & ITU-T G.972 standards. The qualification extends to include the integration of cable joints, optical amplifier units, branching units and other cable accessories which are required to build cable systems. As part of this Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
system qualification process, and usually before international clients will purchase a cable system, a sea trial deployment & recovery of the system components is the last step to be performed to verify the products are fit for purpose. This last step of the qualification process forms the main theme of this paper.
2.2 Customised cable system solutions including specialised cable accessories for the Oil & Gas Industry. These types of products are generally designed and manufactured to client specifications, including ISO 13628-5 API 17E & DNV standards and can involve power, optical, copper data cable units together with high & low pressure tubing lines. As the products are customised to client’s specifications, each project requires a unique design solution which is not sea trialled. The products are verified as suitable for operational use by extensive design calculations, computer modelling of deployment, operational, overload and repair conditions. The products are also extensively tested onshore and undergo a comprehensive Factory Acceptance Test. To meet these extensive requirements Hengtong Marine has invested in a R&D Test Centre which has been constructed to match or exceed the capabilities of other international subsea cable test facilities. This facility is available for use by other companies.
2.3 Customised cable system solutions including specialised cable accessories for Scientific Observation Networks. This suite of products is handled in a similar way to Oil & Gas products described in point 2.2 above. The products generally incorporate multiple power cores and optical units in a customised design to meet project requirements. Extensive modelling, design calculations & onshore testing of these products is required. No sea trial of products is required.
Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
2.4 Customised system solutions for the Defence Industry. Severe restrictions on what can be said regarding these products, but they also follow points 2.2 & 2.3 above. Generally, no sea trial of products is required.
2.5 HV Subsea Power Cables. Products have been developed for offshore wind farm array cables and export cables, together with interconnector cables. Cables are designed and qualified by Type Testing and certified by internationally recognised bodies. Generally, no sea trial of products is required.
As can be seen one of the key differences between relatively standard subsea telecom products and the other customised industry solutions is the requirement for a comprehensive sea trial.
3. Designing an Offshore Sea Trial to meet International Expectations
There are many things to consider when designing a sea trial, as the last stage in the cable system qualification. The following are probably some of the key points for to be considered when planning the sea trial activity. Each of these items will now be discussed briefly.
3.1 What marine operations to sea trial: The key marine operations which should be demonstrated during the sea trial include 3.1.1 armoured cable burial using an industry recognised cable plough. This will cover the plough launch operation, deploying the plough on the cable & lowering to the seabed. The grading into the seabed of the plough share & burial of cable, joints and optical amplifier units. After completion of burial, the recovery of the plough back to the cable ship followed by the recovery of the cable system back on-board. 3.1.2 Surface lay (deployment) of lightweight cables, joints and optical amplifiers with bottom slack control and cable recovery. This trial will show that cables can be handled through the linear cable engine for deployment and through the Cable Drum Engine for recovery operations. 3.1.3 Surface lay (deployment) of a Branching Unit (BU), with three cable legs attached. This trial verifies that the single leg cable (Leg A) can be used to support the BU and the two branched cables (Legs B & C) during deployment & Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
recovery operations. The deployment will demonstrate that the BU will not spin and twist Legs B&C during deployment, due to the cable torsional characteristics of Leg A. A worst case scenario is the deployment and recovery of a BU in deep water using LW cable (where cable tensions will be much closer to the cable NTTS), rather than an armoured BU in shallow water, where there is a much larger factor of safety over cable working tensions.
The relative size and shape of Cable Joints, Repeaters and Branching Units 3.2 Sea Trial Location & water depth: The selection of the sea trial location is critical in that it can affect permits & permissions to operate and transit distance from Port. An open exposed location will give a good test of products (dynamic tension variation due to swell and waves), at the risk of weather delays, while a sheltered location will provide calmer seas (relatively steady tensions) and low risk of weather delays. To be a realistic sea trial for international clients the selected location should tend to be open and exposed, as this will offer a more severe test of the cable system. The water depth will dictate the cable tensions applied to the cables. Hengtong Marine chose to complete a 5000m water depth surface lay trial, a 4000m water depth Branching Unit trial and a 500m water depth plough burial trial. 3.3 Sea trial seabed survey: Is it necessary to complete a full bathymetric and plough burial assessment survey of the sea trial area? This would be a costly exercise both in terms of timescales (separate mobilisation in advance of the system sea trials) and also costs incurred. The survey requirements will also be influenced to a great extent by the marine installer selected for the trials. For the Hengtong Marine Sea Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
trials the marine installer selected was satisfied to carry out an onsite sounding run to determine the seabed profile (slopes) and water depth (in deep water) and to select a separate location for ploughing operations close to existing in service international systems where geophysical seabed parameters where know, and cable burial could be achieved (while respecting the International Cable Protection Committee (ICPC) operational recommendations).
3.4 Timing of the sea trial, weather considerations: Some cable operations are more weather sensitive than others, for example plough burial (launch & recovery operations) are much more weather sensitive (vessel motion) than deep water surface lay operations. There is little point in completing the sea trial when weather conditions are perfect, as the cable system products will not see a realistic test of actual marine deployment conditions & the trial results could be open to criticism by future clients. Likewise, it is pointless to select a time window when weather conditions are so severe that no cable work can be achieved (and the cable ship is on downtime due to weather delays). At Hengtong Marine we waited for a reasonable time period which was considered early in the cable working season, where the risk of some weather delays was expected, but this was tempered by the requirement to achieve a good dynamic test of the cable system products.
3.5 Duration of sea trial, one operation or several separate trials? It is possible to split the plough burial trials and the surface lay trials into two separate operations and to take advantage of vessel availability or different geographical locations. Hengtong decided to complete all trials from the same cable-ship platform and to mobilise all personnel, test equipment and cable systems at one time from the Hengtong Marine Port in Changshu, China.
3.6 Which Cable Types and lengths of cable: Sufficient cable lengths should be supplied to allow the cable ship to deploy the system safely, using industry standard cable working procedures. The system cable should be a mix of cable types, including inline transitions, cable joints and bodies. 3.6.1 For surface lay operations there should be sufficient cable length to allow the cable ship to generate a steady state cable deployment catenary in surface lay mode and to control the cable slack deployed. The distance between optical amplifier bodies should be planned so that one body is on the seabed, before the next body is deployed from the cable-ship. Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
3.6.2 For branching unit deployment, sufficient lengths of cable, should be provided to allow cables to be laid & buoyed off, picked up and for offshore shipboard joints to be made, with system integration the Branching unit on-board the cable ship. 3.6.3 For Plough burial of cables, the armoured cables should be sufficiently long to allow the plough to be launched from the vessel without any joints or other bodies being deployed through the plough during this process. The selected water depth for this operation will also have a major influence on cable lengths required. 3.7 Which Optical Fibre types and number: The cable used on the sea trial should incorporate a wide range of fibre types (different suppliers and specifications) and fibre counts. The Hengtong Marine sea trial used 5 types of optical fibres from 3 suppliers, including the Hengtong G654 & G652D fibres, and cables with fibre counts ranging from 8, 16 and 24 fibres.
Hengtong Marine Fibre In Metal Tube (FIMT) production line 3.8 Which cable features & repairs to be included: The sea trial operation is an excellent opportunity to include some standard cable features, splices and repairs (which have already passed land based testing as part of the qualification process). High strength fibre splicing, in-line tube joints, copper weld repairs, inner armour wires welds, insulation repairs (heat shrink and moulded repairs), outer armour wire welds and inline cable transitions should all be sea trialled.
3.9 Location and type of cable joints: The location of cable joints should be carefully selected so as not to affect marine deployment operations (such as planned plough launch activity, or planned plough recovery positions). Most clients will use the Universal Cable Joint for system maintenance so they usually expect to see this type of joint in the sea trial, together with any supplier propriety factory cable joint designs. Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
Stages in the assembly & build of a Universal Cable Joint
3.10 Location and type of optical amplifier housings: It is important to ensure that the optical amplifier housings used in future system projects are included in the sea trial. Hengtong Marine selected Huawei Marine Networks to supply the optical amplifier housings and incorporated two different amplifier housing designs in the sea trial. Both the HMN R1 2 fibre pair unit and the HMN R2 6 fibre pair unit were incorporated into the lightweight surface lay and armoured cable plough burial trials (4 optical amplifier housings in total). UJs and UQJs cable joints were also included for verification of land based testing carried out by the UJ Consortium.
3.11 Selection of an internationally recognised authority to witness the sea trial: To ensure that an unbiased record events of sea trial operations was maintained it is critical that an independent industry expert is engaged to witness all marine operations, from system loading to system discharge back ashore after all trials have been completed. Hengtong Marine Selected Captain David Foster, a former cable ship commander and recognised international cable expert, with more than 40 year’s experience of system deployments and repair operations.
3.12 Cable loading logistics (single line or twin line): To achieve competitive system load out speeds and timescales, it is a key requirement to minimise cable ship or cable freighter time alongside the cable factory Port. One method of achieving this objective is to utilise twin line loading. This should be included as part of the sea trial plan.
3.13 Cable deployment speeds and tensions: Marine operations should be planned to show that products can be handled, deployed & recovered to industry standard deployment speeds and recovered safely within acceptable cable handling parameters (NTTS, NOTS, NPTS). This requirement impacts the sea trial design including cable lengths, selection of water depth at trials location etc. Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
3.14 Vessel standby times (simulating repair times): Another key requirement is for the cable ship to stand to the cable for a period to allow testing and for cable jointing during repair operations. Under these conditions the cable pay-out is stopped & the cable is suspended from the cable ship, subjected to dynamic cable tensions for a prolonged period of time. During the Hengtong Marine sea trial all cable system trials were subjected to this requirement, with holding periods of 6 hours (testing) and 24 hours (for Branching Unit integration & jointing).
3.15 Cable recovery speeds and tensions: Realistic cable recovery speeds to verify operations can be completed within cable operating parameters (NTTS, NOTS, NPTS).
3.16 Re-use of cables: Most sea trials would use newly manufactured cables and deploy & recover the system once. At Hengtong marine we like to do things differently. It was decided to re-use the LW cable from the 5000m water depth trial, and reconfigure the cables to complete the Branching Unit (BU) 4000m water depth trial.
3.16.1 The BU trial is a more severe test of the LW cable as the single Leg A has to support the weight of the Branching Unit and the other two cable Legs B&C, effectively supporting more than 8000m of cable! Hengtong decided to proceed in this manner to verify the robust cable construction & ability to re-use cables. This test was successful with the re-used LW cable testing good for optical & electrical parameters and with no mechanical degradation or damage. 3.16.2 For the armoured cable plough burial trial in normal operations the plough is normally launched on DA or SA cable just once and recovered on a fresh length of cable. Once again Hengtong Marine chose to demonstrate the robust cable construction by launching & recovering the plough on the smallest armoured SAL cable, not just once but 5 times on the same length of cable! This repeated launch & recovery was to simulate real life problems where plough faults can occur and the plough dive has to be stopped & recovered to deck for repair. This was successfully demonstrated without any mechanical, electrical or optical degradation. Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
3.17 Use of international industry standard cable ships and cable handling equipment and procedures: It is important to select a cable ship equipped with standard international cable equipment and which has a successful track record deploying & repairing international optical cable systems. This confirms that new products can be handled using standard procedures and equipment, without modifications. 3.18 On-board cable system testing parameters & limits during offshore operations: The selection of parameters to test during the trial is essential to demonstrate that the cable system operates correctly and within specification. The cable insulation resistance, conductor resistance, optical fibre attenuation, PMD, output optical power and stability should all be monitored & recorded, during deployment, standby time and recovery operations.
3.19 System unloading (discharge ashore): After the marine operations are complete and the cable ship returns to Port the cable systems should be unloaded to avoid damage and to respect the cable handling parameters (tension, bend radius and abrasion).
3.20 Post sea trial cable examination of cables, joints and Optical Amplifier Units: A detailed investigation, re-testing (optical, electrical & mechanical) and dissection of cables, joints and Optical Amplifier Units is required to demonstrate that the products have not degraded in any way due to the loading, marine operations or discharge of cables back ashore. This is the final quality check to verify products are of the highest manufacturing standard and suitable for use in subsea systems.
4. Analysis of the Hengtong Marine HORC & HOUC cable sea trial The Sea Trial planning actually started more than 1 year before implementation. The cable specifications and fiber types were carefully selected and various sea trial locations were considered. Once the water depths for each of the sea trials was agreed, cable manufacture commenced using a number of different production lines with all cable being completed several months prior to the trials load out date.
Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
Hengtong Marine Composite Conductor Production Lines Ultimately it was decided to integrate the cable systems using the Hengtong Marine “System Integration & Test Area” and utilize twin line loading to verify the load out gantry to Hengtong Port.
Cable System Jointing In Progress on the Integration Area
Hengtong Marine System Integration Area with subsea plant & cable bights Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
When load out operations commenced on 11 April 2017, the Hengtong HV company were also loading out products, so the gantry system & Port successfully demonstrated triple line load outs, showing no conflict been the two cable factories onsite.
Hengtong Marine Port & Gantry, with triple line loading in progress (2 x Telecom, 1 x HV) The marine portion of the sea trial operation covered 30 days of activity over the timeline from 2017.4.11 to 2017.5.10 Hengtong Marine HOUC-1 un-repeatered cable and HORC-1 repeatered cable products were integrated with HMN R1 (2 fiber pair) repeaters & R2 (6 fiber pair) repeaters and Universal Joints & Universal Quick Joints.
Integration of BU, R1 Repeater, R2 Repeater and cable joints into the sea trail cable systems SBSS was selected as the preferred marine operator and the CS Fu Hai was mobilized to Hengtong Port for the project, equipped with a SMD MD3 cable burial plough capable of 2m to 3m burial into the seabed. Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
Three sea trial locations were selected for the trials, generally lying to the South and South East of Japan, in an open exposed Pacific Ocean location.
The 5000m HORC Repeatered system trial was located in the area 28°01'N 134°58’E The 4000m HORC branching unit system trial was located at 28°15'N 133°12’E The 500m HOUC & HORC plough burial trials were located in the area 28°33'N 130°43'E Four separate sea trial systems were manufactured specifically for the sea trials 5000m water depth HORC-1 repeatered system (2fp & 6fp RPTs, 2 x UJs) using 35.830 kms LW & LWP cables
Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
4000m water depth HORC-1 Branching Unit system (PSBU, 5 x UJs) using 25.640 kms re-used LW & LWP cables from the 5000m trial
500m water depth HORC-1 cable plough trial (2fp & 6fp RPTs, 2 x UJs) using 10.350 kms SAL, SA and DA cables
Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
MD3 Plough recovery and Plough Graphic Control Screen showing cable burial 500m water depth HOUC-1 un-repeatered cable plough burial trial (3 x UQJs) using 6.890 kms SAL, SA and DA cables
All four sea trial systems were deployed and recovered successfully, with good cable handling characteristics and all measured cable parameters within specifications. The cable electrical and optical test values remained stable throughout the trials, with some improvement in values when the cable systems were deployed on the sea bed (due to lower seabed temperature). Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
Some valuable lessons can be learned from the timeline of the 30-day duration sea trial as summarized in the following Table
Item Activity
Duration
%
1
Vessel Mobilisation, Cable System Loading / Unloading, Test Equipment, Branching Unit, Jointing Kits, various cable gear, personnel
4 days
13.3 %
2
Transits from / to Hengtong Port to work locations
6 days
20 .0 %
3
Weather delays (mostly related to ploughing & Branching Unit deployment) due to open exposed work location
7 days
23.3 %
4
Cable Work onsite
11 days
36.7 %
5
Cable System testing
2 days
6.7 %
Total duration
30 days
100 %
As with any marine operation the time analysis reveals that transits and weather delays are the most costly non-productive periods of time spent offshore, but this is the required penalty to prove the cable system product performance in realistic conditions close to the limits of commercial cable deployment and repair conditions.
Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802
江苏亨通海洋光网系统有限公司 HENGTONG MARINE CABLE SYSTEMS
Conclusions
Hengtong Marine has succeeded in demonstrating our HOUC and HORC telecom cable products robust structure and excellent handling capabilities using an industry standard cable ship without modifications to equipment or procedures. This activity completes the last step in the qualification of products for the global international market, and demonstrates Hengtong Marine’s objective of delivering “Global Quality from China”.
Acknowledgements
The authors would like to thank HMN and SBSS for excellent co-operation and flexibility in making this sea trial a success and creating a “Win–Win–Win” result for everyone involved. A special thanks to the Hengtong Marine Sea Trial team, comprised of members from Production, Quality, Engineering Services, R&D and Fibre Manufacturing for all their efforts offshore 24/7 and also to Captain David Foster the Independent Marine Observer.
Address ： No 8 Tongda Road, Changshu Economic Development ZoneJiangsu Provence, China Website：www.hengtongmarine.com
Tel：0512-52266895 Postcode：215537
Fax：0512-52266802