Liquid chlorine is unloaded from rail tankers into a storage vessel. To provide the necessary NPSH, the transfer pump is placed in a pit below ground level. Given the following information, calculate the NPSH available at the inlet to the pump, at a maximum flow-rate of 16,000 kg/h. The total

Question

Liquid chlorine is unloaded from rail tankers into a storage vessel. To provide the necessary NPSH, the transfer pump is placed in a pit below ground level. Given the following information, calculate the NPSH available at the inlet to the pump, at a maximum flow-rate of 16,000 kg/h.

The total length of the pipeline from the rail tanker outlet to the pump inlet is 50 m.

The vertical distance from the tank outlet to the pump inlet is 10 m. Commercial steel piping, 50 mm internal diameter, is used.

Miscellaneous friction losses due to the tanker outlet constriction and the pipe fittings in the inlet piping, are equivalent to 1000 equivalent pipe diameters. The vapour pressure of chlorine at the maximum temperature reached at the pump is 685 [latex]kN / m ^{2}[/latex] and its density and viscosity, [latex]1286 kg / m ^{3} ext { and } 0.364 mNm ^{-2} s[/latex]. The pressure in the tanker is 7 bara.

Accepted Answer

Friction losses

Miscellaneous losses [latex]=1000 imes 50 imes 10^{-3}=50 m ext { of pipe }[/latex]

Total length of inlet piping = 50 + 50 = 100 m

Relative roughness, e/d = 0.046/50 = 0.001

Pipe cross-sectional area [latex]=\frac{\pi}{4}\left(50 imes 10^{-3} ight)^{2}=1.96 imes 10^{-3} m ^{2}[/latex]

Velocity, u [latex]=\frac{1286 imes 1.76 imes 50 imes 10^{-3}}{0.364 imes 10^{-3}}=3.1 imes 10^{5}[/latex]

Reynolds number [latex]=\frac{1286 imes 1.76 imes 50 imes 10^{-3}}{0.364 imes 10^{-3}}=3.1 imes 10^{5}[/latex] (5.4)

Friction factor from Figure 5.7, f = 0.00225

[latex]\Delta P_{f}=8 imes 0.00225 \frac{(100)}{\left(50 imes 10^{-3} ight)} imes 1286 imes \frac{1.76^{2}}{2}=71,703 N / m ^{2}[/latex] (5.3)

[latex]\begin{aligned}NPSH &=\frac{7 imes 10^{5}}{1286 imes 9.8}+10-\frac{71.703}{1286 imes 9.8}-\frac{685 imes 10^{-3}}{1286 imes 9.8} \&=55.5+10-5.7-54.4=\underline{\underline{5.4 m }}\end{aligned}[/latex] (5.7)

Question 5.4: Liquid chlorine is unloaded from rail tankers into a storage...

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