The Industry Standard - Vryhof

1 Stevpris Mk 6 The Industry StandardThe range of water depths in whichthe offshore Industry operates isexpanding fast. The requirements forthe mooring of floating units ask for afocus on less weight, higher strengthand ultra holding power, whilemobile units also demand highversatility and HSE-friendliness. In these times of focus it seems a newanchor is being developed for each specificapplication. The majority of offshore projectshowever meet variables in water depth, soils and operational conditions, in all asking exactly the opposite: a genericanchor that suits all purposes. The most used anchorThe Stevpris anchor is just that. Well over8,000 units were employed over some 3 decades. Its 6thgeneration was introducedsome 5 years ago and sold some 1,000 unitssince.

2 Stevpris is the most used anchor in theoffshore design combines the best of 3 worlds:the feed back from numerous anchor installations, a fluke design derived from the Stevmanta deepwater anchor and theinherent robustness of the Stevpris shape. Stevpris Mk6 is superior to all its predecessorson all of its versatileStevpris Mk6 Stevpris Mk6 design stems from the flukedesign developed for the Vertical LoadAnchor anchor Stevmanta, pictured here balanced designThe anchor's geometry provides an extreme highweight/strength ratio. The fluke shape minimizes soil disturbance and its large surface provides the huge holding power that is well in excess of 30% more than that of any other drag anchor today. The design istype-approved by major Classification Authorities.

3 Uplift capabilityStevpris Mk6 has superior uplift capability. On a case to casebasis uplift is allowed of 5 degrees in intact condition and10 degrees in damaged condition. API rules suggest an upliftof 20 degrees, proven in tests to be possible without losingholding power. The uplift capability significantly increasesthe range of water depths in which rigs can operate on thesame anchor spread. Stevpris Mk6 The Industry Benchmark 1234651 Anchor head improves handling2 Shackle is positioned inside the anchor head, no more interference with the chaser 3 Wide spread shanks and redesigned geometry improve penetration, stability and strength4 Design improves stability on stern roller, during deck handling and is HSE friendly5 Fluke angle is easily adjustable to soil conditions6 Redesigned fluke for better stability and penetration7 Larger fluke surface assures superior holding capacity and shorter drag8 Hollow fluke for ballasting if needed9 ABS & DnV Type Approval10 Stevtrack inside (Optional)

4 98710 Easy handling Some of Stevpris key improvements derivedirectly from a drilling operator s wish list but its generic character suits evenly well for permanent moorings, dredging plant and marine construction applications. The widely placed shank plates serve correctarrival at the AHV stern roller while the widefluke provides stability on the seabed as wellas during penetration. Placement of theshackle between the shank plates preventsinterference with the chaser. The fluke anglecan easily be adjusted to 3 different positionsto match different soil retrievalThe shank head improves locking the chaser before breaking the anchor it holds the anchor steady duringhauling and with the chain or line held inthe fluke V-shape the anchor orientation islocked for easy racking or decking.

5 Overall, the compact sleek design allows easyhandling on deck and proves Stevpris Mk6 fits most anchor racks. Forreplacement orders or new builds, Vryhof canassist with dedicated rack arrangement most used anchor today. Extreme holding power due to wider fluke and deeper penetration Ultimate structural integrity withstands the toughest conditions Design facilitates easy handling,fits most anchor racks Accommodates the widest rangeof soils possible Excellent stability due to slim design and easy Mk6 Easy handling & installation Easy HandlingVersatile applicationDue to their versatility Stevpris anchors serve a wide range ofmooring applications. Although the large majority serves themooring of offshore units such as drilling rigs, FPSOs and SPM buoys they are also widely used for various dredging, crane and pipelay vessels.

6 Currently a set of Stevpris anchors is employed for the mooring of a floating windmill. Purchase, lease or rentalIn order to meet Opex or Capex criteria, Vryhof 's anchors can besupplied on a purchase, lease-purchase or rental basis. Within astrategic alliance with major mooring component manufacturers, Vryhof can design and supply complete mooring a complete (pre-laid) mooring system could wellbe a consideration for your next mooringsMaximum operability is achieved by pre-installing a mooringspread, allowing the rig to hook-up at arrival. Rig operators thisway significantly save on time normally lost on paying out thefull spread. By relocating mooring spreads ahead of a rig movethe operator can significantly increase the number of operationaldays in a drilling programme.

7 Vryhof holds a stock of anchors for rental in strategiclocations around the Mk6 The system, named Stevtrack Anchor DataAcquisition System, consists of a transponderon each of the anchors, a set of signal transmission equipment and a surface read-out computer. Live image, factual dataThe moment the anchor touches the seabed, the transponder in the anchor transmits to the read-out unit on deck. It provides accurately the orientation of the anchor: its pitch and its roll. Stevtrack confirms the anchor has arrived in the correct position or allows repositioningby the AHV with a single haul, loosing notime. This alone can save a full day, a verysubstantial part of the mooring spreadinstallation that now can be completedaccording to schedule.

8 Stevtrack s read-out unit runs on proprietaryWindows compatible software with a graphicalinterface. The system provides in real-time a reliablerepresentation of the installation process athand in the seabed and accurately reportsload on the anchor, depth and drag lengthuntil final penetration. The pulling forcemeasured at the anchor is far more accuratethan that read on the AHV winch. Stevtrackmay therefore also serve to justify the proofloading otherwise required by theQualification insideStevtrack is fully operational and available asan option on newly supplied Stevpris Mk6anchors. Stevtrack witness of successVryhof Anchors has solved thedilemma on drag length versus final anchor position. For years acalculation method served todetermine a drag anchor s finalmooring position.

9 The increasingrequirement for factual data inspiredthe development of a monitoringsystem that provides more traceabledata than available on any otheranchor in the StatisticsUltimate holding capacityStevpris Mk6 weight in metric tonsin metersin metric tons UHC in medium clayUHC in very soft clay (mud)UHC in sand & hard claypenetration in medium claypenetration in very soft claydrag in mrt. in very soft claydrag in mrt. in medium claydrag in mrt. in sand & hard claypenetration in sand and hard clayThe prediction lines on the UHC chart representthe equation UHC= A*(W) UHC as theultimate holding capacity in tonnes and A aparameter depending on soil, anchor andanchor line with values between 24 and design line very soft clay represents soilssuch as very soft clays (mud), and loose andweak silts.

10 In very soft soils the optimumfluke/shank angle is typically 50 deg. The Stevpris Mk6 very soft clay design line is applicable in soil that can be described by an undrained shear strength of 4 kPa at the surface increasing by kPa per meter depthor in the equation Su = 4+ *z. with Su in kPaand z being the depth in meters below design line sand represents competentsoils, such as medium dense sands and stiff tohard clays. In sand and hard clay the optimalfluke/shank angle is 32 . The Stevpris Mk6design line is based on a silica sand with amedium density. The medium clay design linerepresents soils such as silt and firm to stiffclays. The fluke/shank angle should be set at32 for optimal performance. Post installation dataStevtrack also allows monitoring post-installationbehaviour of the mooring system, measured at intervals depending on battery capacities.