RV Investigator Long Core System. Mark Lewis. Senior Mechanical Technician

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1 RV Investigator Long Core System Mark Lewis. Senior Mechanical Technician

2 Overview My experience with these systems is limited so I have been talking to as many people around Australia and New Zealand as I can as well as overseas including helpful staff from IPEV, IFREMER and NIOZ and web searches on a few other institutions. My principle reason for being here is to get as much information as I possibly can about how to get the best out of our system.

3 Marine National Facility Abstract The RV investigator has purchased a long core system from SEAS Australia. The vessel deploys the system from a Triplex overhead boom, core head handler and twin cranes to support the barrel. The core barrel used is drill pipe capable of having a 100mm outer diameter liner inserted. We have both polycarbonate and PVC liners. The system is capable of having 24 metres of barrel and being used in either gravity or piston mode. The main coring cable is 24mm dyneema, 8,400m long with a maximum working load of 20 tonnes. Theoretically our system is capable of retrieving 24 m cores from 7,000 m water depth. To date the system has only been used on a few research voyages and after tuning has retrieved up to 10.2m of core in gravity mode (12m of barrel) and 13.62m of core in piston mode (15m of barrel). Our piston is in two parts and capable of using a range of shear pin sizes.

4 Background The system we have was purchased through a technical advisory group that sought information from a wide range of experts and potential users Triplex were selected to supply the hydraulic systems to launch and retrieve the corer SEAS Australia were selected to supply the coring system RAPP HYDEMA supplied the main coring winch and cable

5 Core Handling System The triplex system consists of: Overhead boom with upper and lower auxiliary winches Two corer davits One LARS

6 7 t upper auxiliary winch Photo of Overhead Boom Coring Sheave 0.5 t lower auxiliary winch

7 Overhead Coring Boom The over head boom has both a lower and upper auxiliary winch as well as the main sheave for the 24mm cable The boom has a lifting safe working load of 30 tonnes and a side towing capacity of 1 tonne The upper auxiliary winch is used to handle the piston cable (35m of 26mm cable) and has a working load limit of 7 tonnes so is capable of lifting the entire core rig in piston mode The lower auxiliary winch is used for lifting piston core components such as the trigger weight, trigger mechanism and pilot core It has a working load limit of 500 kg

8 Triplex corer davit

9 Corer Davit The davit has a Working Load Limit (WLL) of 2.4 tonnes The first davit is positioned to handle the first m of core barrel The second davit handles the rest of the core barrels up to 24 m Each davit can be controlled individually or can be electrically linked and driven from one controller

10 LARS with head weight (6 weights)

11 Core Head Handler (LARS) The LARS has a WLL of 5 tonnes Two sections of the bulwarks need to be removed to deploy the system The unit is hydraulically driven clear of the vessel Once clear the unit can either be driven around to vertical or put into a free mode where the weight of the core barrel causes the head to rotate The latter mode only works if the weight of the head and the core barrels are matched

12 Coring Winch The winch is transverse mounted in the scientific winch room on the first platform deck. The cable runs up to 02 deck via a cable trunk, and out to the base of the coring boom The cable can also be run aft from the cable trunk for over the stern operations The coring winch was supplied by Rapp Hydema and has a WLL of 30 tonnes It is a fully electric winch capable of automatic heave compensation The cable is 24mm Kapaneema SK 75 Dyneema with a WLL of 20 tonnes The cable is 8,400m long The minimum break load is tonnes

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14 Drive Motors

15 Spooling Gear

16 Head Weight The stem of the head weight is 130 kg and each weight is 260kg The stem is capable of holding 10 weights When rigging in gravity mode a valve is bolted between the weight stem and the barrel flange When rigging in piston mode the piston stops are bolted between the stem and flange after the piston cable has been fed through Total weight can be over 3.2 tonnes Barrels The barrel is constructed from 3 m sections (65kg) of drill pipe with an internal diameter sufficient to allow 100mm liners

17 Core cutters We have the standard simple cutter that utilises fingers to retain the core The old fingers were 0.3mm and the new ones are 0.5mm 304 spring stainless

18 The second style of cutter is a cam shell retainer with a long cutter head The cam shell style utilises the pull out force to close the clams and retain the core

19 Photos of the core cutter in the open position, then when closed Core barrel adapter Core cutter pivot bolt Grub screw covering the core cutter mount Retainer activation fingers Core cutter

20 Lower section of Upper Piston Shear pin hole Lower Piston Retainer Ring Piston Seal Ring-1 Glide Ring Piston Seal Ring-2

21 Brass Shear strength 234 Mpa* Diameter (mm) Strength, double shear 1, , , Strength, double shear (kgf) Spring Steel Shear strength 1380 Mpa* Diameter (mm) Strength, double shear 8, , , Strength, double shear (kgf) , ,536.71

22 Core length Number of 3m core barrels Number of weights on Piston Corer Piston Corer Total Weight Weight required (F1) to Balance Total Trigger weight Number of Weights Required n1 n2 F2 F2 * d2 / d1 F1 t1 TOTAL System Weight (m) (kg) (kg) (kg) (kg) (30kg each) (kg) W , , , , , , , , , , , , ,660.0

23 The system in piston mode showing the trigger mechanism clamping onto the piston cable and the head weight The pilot core hangs off the trigger arm The amount of freefall is determined by the loop of piston cable between the clamp and the core head

24 Trigger mechanism Trigger or Pilot core

25 Piston core release arm

26 Barrel gripper supplied with the Triplex system

27 New barrel gripper It is lighter and slides up and down the pipe a lot easier

28 The Core being deployed in gravity mode with 6m of barrel Core is rotated, lifted out of the LARS then deployed down to 100m above the sea floor After stabilising at 100m up we lowered the core into the seafloor at 60 m per minute On later voyages we slowed this to 30m per minute as we had suffered pipe breakage after some faster deployments

29 Free fall and recoil We have decided to use 3m of free fall Cable recoil was initially discounted as we are using a low stretch polyamide rope Kapaneema dyneema SK-75 (MBL t) After contacting the manufacturer I obtained some basic data on expected stretch with load and calculated the formulae: %S=0.0006(core wt t)^ (core wt t) Elongation at failure was stated as 5% On the deployment to 3,100m of water we allowed 3m of freefall and 3m of recoil (calculated at 0.03% but we used 1% stretch) so the piston cable loop was 6m long

30 Gravity mode Our best result so far is 10.2m of core out of 12m of barrel with a 2.21 tonne head weight 30m per minute into the seafloor Piston mode This system uses a 2 part piston with facilities for 2, 3 or 4mm shear pins At this stage we are still testing different sizes and materials for the shear pins Best result was using a 2mm brass and a 3mm spring steel pin (2,139kg) with 15m of barrel and 2.21 tonnes of weight 13.62m of core was returned with piston still at the water sediment interface from 3,100m of water and 15m of barrel

31 Conclusions The system is relatively new to my team and we have had some good results, interspersed with some interesting ones Some results have been disappointing i.e. when the fingers in the cutter had reversed and the sample been lost We have since increased the strength of the fingers and had good results in a mixed clay/sandy substrate On another occasion the cam jaws were still open and no sample had been retained Upon inspection of the jaws were found to have tried to close but damage in the centre indicated that a rock had held them open causing the closing levers to bend and distort the pivot screws

32 Feedback please Penetration speed into the sea floor The amount of recoil in polyamide ropes The strength of shear pin to use in 100mm diameter core pipe and if this should vary for different sediments Barrel gripper design Types of steel used in the retaining fingers of the core catcher Internal diameter of the core cutter compared to the internal diameter of the core liner

33 Thank you for your attention Questions? For further information: Mark Future Lewis research vessel project CSIRO, O&A Hobart.