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Excursions Challenges! Excursions Challenges!

Excursions Challenges! - PowerPoint Presentation

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Excursions Challenges! - PPT Presentation

Excursions Challenges 13 th March 2013 Arnfinn Anfindsen Diving ManagerNorway BackgroundHistory Excursions as per Norsok U100 Various scenarios A Working in a trench B Welding HabitatH ID: 764356

diving excursion maximum excursions excursion diving excursions maximum depth norsok min subsea decompression working time living u100 bell safety

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Excursions Challenges! 13 th March 2013 Arnfinn Anfindsen Diving Manager-Norway

Background/History Excursions as per Norsok U100 Various scenariosA – Working in a trenchB – Welding Habitat/H-FramesC – Subsea ManifoldD – X-Tree Protection coverAn Offshore Managers FrustrationUK Unlimited Excursion TableReferences Agenda

History /BackgroundFacts: Vessel : DSV Seven PelicanOperation: B11 Bypass Project preparatory work (German Sector)When: May 2012Seabed dept: 32ms before excavationOperational issue:  Limited excursions for given depthSafety issue: Diving bell, stage and clump weights located minimum 2 meters above seabed Deviations:    Norsok U-100 section 8.2.3.4, and  to Subsea 7 Saturation Diving Manual Chapter 10

Procedures for excursions shall be prepared. If excursions are extended compared to Table 8, longer stays at living depth prior to start of decompression should be considered. Decompression shall not start with an upward excursion. There shall be a minimum 8 h hold at living depth prior to decompression after an excursion.Norsok U100 8.2.3.4 Excursions

As a minimum, the procedures shall define;a) living depth,b) working depth,c) limitations of excursion after change of living and/or working depth,d) maximum rates for compression and decompression during excursion,e) maximum pressure increase and decrease during the excursion. It is of special importance to restrict the use and distance of upward excursions. The maximum ascent rate during excursion is 10 msw/min.

Selection of Excursion Types and Distances – Norway Usually, it will be possible to select one of several different storage depth/excursion scenarios for carrying out a specific job. As a general rule, choose the storage depth which minimises ascending excursion distances during the dive operation. Thus, prefer:Descending excursions rather than ascending excursions.Storage depth as close to the working depths as practical. In order that operational excursion distances are not affected by the distance between the two, they should be as close as practical.Planning of the dive is essential!

Diving Excursions – Table 8

Diving Excursion - Working in a trench

Bell door -27 mswBottom of clumpweight -30 msw Min 3 m Min 2 m Excursion needed 9 m 4 m Norsok U100 5m excursion based on LD 27m 5m

Diving Excursion – Umbilical Length Umb. length: ~28mBottom of bell : ~28m

How to obtain consensus for proposed solutuion Involvement of the following personnel is essential;Diving Responsible Doctor - Contractor Health Department– Contractor Offshore Manager Safety Delegate Divers Contractors HSE Department Contractor Diving Manager Company Responsible Diving Doctor Company Diving Advisor Company HSE Dep

Excursion - solutionDivers maximum in water time 4 hours (vs normal 5,5 hours) to avoid Jo-Jo effect during break for rest break, and to reduce total time at maximum excursion depthIncrease hold period from 8 hours to 12 hours prior to final decompression The diving procedure for extended downward excursion  will include following: Storage dept 27 MSWWorking depth, from 32 to 36 MSWThere is no changes in divers living or working depthsThe maximum ascent rate during excursion is 10 msw/min.Maximum pressure increase and decrease during the excursion is within following window: 3.7 to 4.6 ATA.There is no plan to use upward excursions and should this be necessary there will be no changes to limitations as described in NORSOK U-100.

Client B – Welding Habitats/Lifting Frames

Client C – Subsea Manifold 6mBottom of clumpweight -112 msw Bell door -109 msw Min 3 m Excursion needed 12 m Min 3 m Top of manifold 115m

Client D – X- Tree Protection StructureExcursion needed15 m11m Min 3 m

An Offshore Managers frustration“I am fully aware of all this and more, which is my whole point. The best way to deal with a hazard is to remove the hazard. We could effectively do this by raising the bell, i.e. changing the excursions.With the current restrictions we only have 1.7 metre vertical separation, it is not often in the North sea that the sea state is less than that.  Everyone keeps quoting “set up for drift off“ etc. etc. No one has mentioned drive off, which can be in any direction.The simple solution is to allow some tolerance in the excursions. There is as you are aware a precedent for this as both Norsok U100 and our Subsea 7 diving Excursion tables has tested that.Why can’t we get a similar decision to enhance safety? I am having safety, safety, safety pointed out to me time and time again, yet time and time again  beach support is “safetying” us into less safe situations. “No one seems to want to listen to the people who are doing the work.” «NN»Offshore ManagerSubsea 7 DSV

UK « Unlimited» Excursion Tables StorageDepth StandardDescending Excursion Ranges Standard Ascending Excursion Ranges Maximum Descending Excursion Ranges Maximum Ascending Excursion Ranges   10-17 m 18-19 m 20-22 m 23-29 m 30 m 31 - 33 m 34 - 39 m 40-59 m 60-79 m 80-99 m 100-119 m 120-139 m 140-179 m 180-350 m     3 m 4 m 4 m 5 m 6 m 7 m 7 m 8 m 9 m 10 m 11 m 12 m 13 m 15 m     2 m 4 m 4 m 5 m 6 m 7 m 7 m 8 m 9 m 10 m 11 m 12 m 13 m 15 m     Forbidden Forbidden 8 m 10 m 12 m 14 m 14 m 16 m 18 m 20 m 22 m 24 m 26 m 30 m   ForbiddenForbiddenForbiddenForbiddenForbiddenForbidden14 m16 m18 m20 m22 m24 m26 m30 m  Subsea 7 has wide operational experience in shallow saturation diving on the Southern part of the UK, Dutch and German sectors in the North Sea using Subsea 7 Sat Diving Manual UK Excursions (US-Navy). Subsea 7 has not experienced any decompression sickness or other injuries from the high number of dives performed from dives performed on this table.

References Norsok U100 section 8.2.3.4 ExcursionsSubsea 7 Group Diving Manual  Vol 2 – Diving Techniques clause 2.8.2 Excursion LimitsOD 91-88 (Eng) Comparison of Saturation diving tables and preparation of Framework for standardisation of tablesOD 91-12 (NO) Rapport om sammenligning av metningsdyddetabeller og utarbeidelse av rammebetingelser for standardisering