Anchoring Environmental Load Calculator

OCIMF method · Wind + Current + Wave-drift vs Holding Power · Planning estimate only

1 · Vessel

Vessel

Condition

LBP 320 m · B 58 m · T 22 m · A_T 1,740 m² · Typical HHP anchor 19.5 t

2 · Wind

Wind speed (kn)

Anemometer height (m)

Wind dir. rel. bow (°)

3 · Current

Current speed (kn)

Measured at depth (m)

Current dir. rel. bow (°)

Water depth (m)

4 · Waves

Hs (m)

Mean wave period (s)

Wave dir. rel. bow (°)

Wave drift override (t, optional)

5 · Anchor · Seabed · Chain

Anchor type

Seabed

Anchor weight (t)

Yaw amplitude (°)

Chain diameter (mm)

Chain grade

Chain stopper in use

GREEN – HOLDING WITH MARGIN

Loads within holding power and brake capacity. Maintain anchor watch and re-check if weather deteriorates.

Load vs Capacity

Dynamic load / anchor holding power89%

Static load / anchor holding power44%

Dynamic load / windlass brake41%

Results

Wind speed at 10 m	17.21 m/s
CXw	0.850
Wind force	28.6 t
Current K · mean Vc	0.992 · 1.021 m/s
CXc	0.0753
Current force	28.9 t
Wave drift	12.0 t
Total static load	69.4 t
Yaw factor	2.00
Total dynamic load	138.8 t
Seabed factor	8
Anchor holding power	156.0 t
Chain breaking load	7308 kN
Brake holding capacity	335.4 t

Method

F_Xw = ½·C_Xw·ρ_a·V_w²·A_T (ρ_a 1.28, V_w corrected to 10 m by 1/7 power law) · F_Xc = ½·C_Xc·ρ_w·V_c²·LBP·T (ρ_w 1025, V_c = mean current over draught, factor K) · wave drift F = (1/16)·ρ·g·H_s²·B·R(λ/LBP)·|cos θ| · holding power = anchor weight × seabed factor · yaw: 20° → ×2, 40° → ×3 · brake = 45% (stopper) / 80% of chain breaking load.

Source: OCIMF Estimating the Environmental Loads on Anchoring Systems (2010) · OCIMF Anchoring Systems and Procedures · IACS UR W18/A1.

Indicative planning estimate. Not a design tool. The Master's judgement, Class rules, OCIMF guidance and company SMS always take precedence. seawayman.com accepts no liability for decisions made using this estimate.

Seabed Factors

Holding power = anchor weight × factor

Seabed	Stockless	HHP
Shingle / Sand	3.5	8
Rock with thin mud layer	1.8	2.4
Soft mud	1.7	6
Blue clay	2.7	12

Source: OCIMF, based on UK Admiralty trial data.

OCIMF Reference Vessels

Vessel	LBP m	T L/B m	AT L/B m²
Products Tanker 37,000 dwt	175	10.8/6.8	675/760
Aframax 113,000 dwt	239	13.4/8.3	1,290/1,580
VLCC 305,000 dwt	320	22/9.8	1,740/2,460
LNG 150,000 m³ Prismatic	275	11.5/9.5	1,550/1,630
LNG 210,000 m³ Prismatic	302	12/9.6	1,586/1,706
LNG 260,000 m³ Prismatic	332	12/9.6	1,698/1,827