# Menghitung Minimum Bollard Pull Requirement

Untuk menghitung Bollard Pull dengan muatan 4000 Ton dengan tongkang 300ft x 80ft x 18f

Bollard pull (tons) = [(D^2/3 * v^3)/7200 + (Cmv*B*D1)]*K

where:
D = Displacement of the tow (t)
v = Towing speed in knots
Cmw = coefficient for the mean wind speed
B = Width of the tow (m) (transverse to movement)
D1 = Height of the wind facing area above water level, incl. Deck cargo (m)
K = Factor 3 – 8, depending to the circumstances

Ordinary towing conditions (BFT. 4)
V = 6 knots
Cmw = 0,0025
K = > 3

Say, Cargo Displacement (misal = 5535 Ton)
K = 3
V = 6 knots
Cmw = 0,0025
B = 24.4m
D1 = 5 meter

By using the above formula, we got minimum Bollard Pull = 29.076 Ton

Secondly, if we are using DNV or ND or KPM calculation base on current condition:
Wave Resistance (Hs) = 2 meter (Fwave = 15.6 tons; Fmosses =0.528)
Wind Resistance (Ws) = 20 knot (10 m/s where Fwind = 20.5 tons)
Current = 0.5 meter (Fwave = 3.9 tons)

Then
Total Bollard Pull Requirement = Hs + Ws + Current = 40 Tons
If we apply effesien offshore standard 0.75 then we have to provide 53.33 Ton Bollard Pull (equals with 4000 BHP Towing Tugs)

Now it is your choice to confine the customer about the situation since:
1) The above formulation is a fair enough as all the factors related to the barge + tug speed + sea condition + weather condition are involved
2) The formulation just base on sea condition and weather condition.