... A tanker carrying toluene is unloaded, using the ship’s pumps, to an on-shor
ID: 504823 • Letter: #
Question
... A tanker carrying toluene is unloaded, using the ship’s pumps, to an on-shore storage tank. The pipeline is 225 mm internal diameter and 900 m long. The pipe roughness is known = 0.046 mm R. Miscellaneous losses due to fittings, valves, etc., amount to 10 equivalent pipe diameters (i.e., head loss), see question 1 regarding “head loss”. The maximum liquid level in the storage tank is 30 m above the lowest level in the ship’s tanks. The ship’s tanks are nitrogen blanketed and maintained at a pressure of 1.05 bar. The storage tank has a floating roof, which exerts a pressure of 1.1 bar on the liquid. Question: The ship must unload 1000 tonne within 5 hours to avoid demurrage charges. Estimate the power required by the pump. Take the pump efficiency as 70%. Physical properties of toluene: density 874 kg/m3 , viscosity 0.62 cP. ... A tanker carrying toluene is unloaded, using the ship’s pumps, to an on-shore storage tank. The pipeline is 225 mm internal diameter and 900 m long. The pipe roughness is known = 0.046 mm R. Miscellaneous losses due to fittings, valves, etc., amount to 10 equivalent pipe diameters (i.e., head loss), see question 1 regarding “head loss”. The maximum liquid level in the storage tank is 30 m above the lowest level in the ship’s tanks. The ship’s tanks are nitrogen blanketed and maintained at a pressure of 1.05 bar. The storage tank has a floating roof, which exerts a pressure of 1.1 bar on the liquid. Question: The ship must unload 1000 tonne within 5 hours to avoid demurrage charges. Estimate the power required by the pump. Take the pump efficiency as 70%. Physical properties of toluene: density 874 kg/m3 , viscosity 0.62 cP. ... A tanker carrying toluene is unloaded, using the ship’s pumps, to an on-shore storage tank. The pipeline is 225 mm internal diameter and 900 m long. The pipe roughness is known = 0.046 mm R. Miscellaneous losses due to fittings, valves, etc., amount to 10 equivalent pipe diameters (i.e., head loss), see question 1 regarding “head loss”. The maximum liquid level in the storage tank is 30 m above the lowest level in the ship’s tanks. The ship’s tanks are nitrogen blanketed and maintained at a pressure of 1.05 bar. The storage tank has a floating roof, which exerts a pressure of 1.1 bar on the liquid. Question: The ship must unload 1000 tonne within 5 hours to avoid demurrage charges. Estimate the power required by the pump. Take the pump efficiency as 70%. Physical properties of toluene: density 874 kg/m3 , viscosity 0.62 cP.Explanation / Answer
Cross sectional area = r2 = (0.225/2)2 = 0.0398 m2
Minimum Velocity of toluene = [(1000 * 1000) kg /(5*36000) s]*[1/0.0398 m2]*[1/874 kg.m-3]
= 1.6 m.s-1
Reynold's No = (874 kg.m-3 * 1.6 m.s-1 * 0.225 m)/(0.62 * 10-3 N.m-2.s) = 5.1 * 105
Relative roughness = 0.046/225 = 0.0002
From the Friction vs Reynold's no and relative roughness graph we get f(Frictional Factor) = 0.0019
Total length of pipeline = 900 m + 10*0.225 m = 902.25 m
Frictional Loss in pipeline (Pf) = 8f(L/d)(u2/2) = 8* 0.0019* (902.25/0.225)* 874* (1.62/2)
= 68188 N.m-2
Maximum difference in elevation = 0-30 = -30 m
Pressure difference = (1.05-1.1)105 = -5000 N.m2
Energy balance = 9.8(-30) + (-5000/874) - (68188/874) - W = 0
W = -377.74 J/kg
Mass flow rate = (1000*1000)/(5*3600) = 55.56 kg/s
Power = (377.74 * 55.56)/0.7 = 29981 W
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