Mid-Line Buoy Installation Procedure

Mid-Line Buoy Installation Procedure

  1. Deck arrangement on boat should include : Anchor buoy pendant pre-spooled on work drum, mid-line wires faked, stretched, or set in bight-coils to free run.
  2. Once in position alongside rig, spool length of anchor wire from rig onto work drum to equal the pay-out from the pipeline position to the proposed anchor position. Measurement can be by drum counter, deck stripe marking, or run out and measure by NAV system and recover. (If by run out and re-spool, direct operation away from pipeline).
  3. Run out to position over pipeline while rig pays out wire. Deck work should, if possible, be done on rig side of pipeline to avoid DROPS over asset.
  4. Vessel stops just before stern is over pipeline position, rig to hold wire on brake (not full brake, in case emergency slack is necessary).
  5. Vessel connects mid-line buoy clamp in marked position and attaches appropriate wire length to keep anchor wire off asset without requiring buoy to be pulled under surface of water when anchor line is tightened. (It is preferable for clamp to be set a little long as opposed to short). BOAT SHOULD HAVE WIRE SECURED BY TWO MEANS WHILE MEN WORKING IN VICINITY OF WIRE. MID-LINE WIRE IS OR WILL SOON BE RIGGED TO FREE RUN.
  6. Clear work deck of personnel, tension work drum, lower forks or pin arrangement, and start to set out remaining wire under slight tension while proceeding toward anchor location. Mid-Line arrangement will free run off deck and buoy should launch in same manner.
  7. Continue on to anchor location whilst slacking wire from work drum, connect anchor, and pendant stored on drum. RIG TO SHIFT WINCH from brake to clutch and prepare to haul at this time.
  8. Launch anchor to stern roller, lower same to seabed under moderate tension.
  9.  As anchor nears bottom with flukes oriented down (wire under moderate tension) rig begins a slow haul while anchor is lowered (or backed into) to seabed.
  10. Once anchor has bitten, and is holding, vessel to attach pendant buoy and launch same after rig confirms anchor is still holding. (Rig should maintain full tension while anchor vessel is attaching buoy to ensure good hold and prevent vessel from dislodging anchor).

Recovery of Mid-Line Anchor Buoy

  1. Rig will have slacked anchor lines before raising hull to prevent over tensioning.
  2. Chase and recover pendant buoy at anchor.
  3. Heave up, deck, disconnect, and secure anchor.
  4. Attach rig anchor line to work drum and spool in as vessel backs down toward rig until mid-line buoy is on deck. Secure buoy.
  5. Pay out slightly until mid-line pendant can be detached. Detach same.
  6. Rig to spool in as anchor vessel backs toward rig until one ship length off.
  7. Anchor vessel pays out remaining anchor wire from work drum as rig spools wire back on winch.
  8. Anchor vessel passes bitter end to rig (likely by crane).
Roger Dutton

About Roger Dutton

Roger Dutton: Managing Partner at ORMI, Master Mariner, OIM Unrestricted, 1600 Ton Master, Author of textbook: "Introduction to Practical Rig Moving." He has 25 years experience with over 250 Jack-Up rig moves worldwide. He is the Principal Instructor, Dutton’s Rig Moving School with thousands of scale model rig moves.
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