Gas Cargo Calculation Exercise

Gas Cargo Calculation exercise

• Cargo in tanks 2 Ps & Sb • Tanks are loaded with Propylene • Soundings (ENRAF gauges) 2Ps 7352mm

• Tank pressure: 2.60 barg • Patm: 995 mb

2Sb 7480mm

• Cargo tank temperatures 2Ps -15.5 -24.2 -23.9

• Ship’s data – Trim: 1.5 meters by the stern – List: 0.5° to Sb

2Sb -16 -24.7 -23.8

• Height of the tank 10.50m (Ps & Sb) • 100% capacity 1400.35 m3 each tank

Calculation average liquid and gas temperature

Correction of soundings Dip = Thermal Contraction or expansion of the measuring tape Float = Correction for change in float immersion for different densities

Correction for trim & list

Calculation actual volume & mass in the liquid phase Liquid volume x shrinking factor x liquid density

Calculation gas height & Weighed average tank temperature Weighed average tank temperature = ((liquid height x liquid temp.) + (gas height x gas temp.))/Total height of the tank. Used to obtain the shrinkage factor for the complete tank

• Weighed Av.temp. Ps: ((7412mm x 24.05°C) + (3088mm x -15.5))/10500 = 21.53 • Weighed Av.temp. Sb: ((7543mm x 24.25°C) + (2937mm x -16.0))/10500 = 21.89 • (-21.53 -21.89)/2 = - 21.71

Calculation of the gas density

• • • • • • • • • • •

(Ps x Vs)/Ts = (Po x Vo)/To s = standard o = observed n = number of mol, Mm = moleculair weight Dg = gas density Ps = 1.013 bar Vs = n x 23.6451 lit/mol Ts = 288K Po = 2.6 bar + 0.995 bar = 3.595 bar Vo = (n x Mm)/Dg = (n x 42.08 kg/mol)/Dg Dg = (42.08 x 3.595 x 288)/(1.013 x 257.25 x 23.6451) = 7.07 kg/M3

Final result