ANCHOR WINCH

OFFSHORE MOORING EQUIPMENTS

In anchor job operation we need following equipments for mooring the anchors on seabed.

Anchors
Chain
Kenter & Connectors
Wire
Chaser & Grapnels
Fibre Rope
Shackles
Buoys
Swivels
Spin Buoy

PENNANT BUOY RADIUS

Normally, Once we dropped anchor to the seabed it will be followed by splashing the anchor buoy to the water. Well, to identify whether the anchor is drag or not, we have to figure out what is the normal radius of the pennant buoy from the drop point so that it will be easy for us to realize it. Here below, I try to show you how to calculate it by using simple phytagoras formulae.

R= Buoy Radius

w= Length of wire

d= depth of water

Example: water depth is 45 meters and pennant wire lenght is 90 meters so the radius will be 44.7 ~ 45 meters

If the actual radius is greater than tolerance radius calculated and getting shorter to the barge/rig, means the anchor has experiencing for dragging. In this case, we have to reposition the anchor immedietly to avoid any danger such as submarine pipelines surrounding.    

It is simple..isnt it..? you can practice now.

CATENARY FORMULAE

 Catenary is A curve used for:    

• To show Touch Down point at various tension
• §To check minimum clearance over pipeline
• To know how much wire to run

2 Types of Catenary curve

• Static curve (anchor on seabed)
• Running curve (anchor on boat)

COMPONENT TO CALCULATE CATENARY CURVE

• §Table of yperbolic function
• §Distance fairlead to seabed
• §Suspended lenght of wire or chain
• §Weight per meter of wire or chain
• §Tension at fairlead or winch (tension meter)
• §Water depth
    

Touchdown Point

D= [T/W-d] cosh [(T/W)/(T/W-d)]

D=Distance of touchdown point

T=Tension of wire or chain

W=Weight per meter of wire or chain

d=Depth from fairlead to seabed

Suspended Length

Minimum Lenght to Deploy

Tension Formula

Measuring For Chain Mass Per Meter

MASS (in kg/m) = 0.0219 x diameter² (d in mm)

Measuring For Proof and Breaking Load

LOAD (in kN) = coefficient x d²x (44 – 0.08xd)

ANCHOR TYPES

• •Poor anchors : Danforth, LWT, Vicinay, non offshore type
• •Good anchors: Stevpris, Bruce FFTS, Bruce TS, Stevin, Flipper Delta

•The anchor must always be tested after running. Heave the winch to 1/3 BS and hold for 15 mins, then slack to working tension

•Depth of burial very important and soil type. The modern anchors have much larger fluke area and are also designed to bury very deeply

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These modern anchors however must be handled properly



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Holding Power In Mud

 Holding Power In Sand