Minnesota Boiler License Practice Exam

What is the pressure of oil in a discharge pipe at ground level, given a tank filled with #6 oil, 110 feet high and 70% full?

1. 31.1 PSIG

2. 33.3 PSIG

3. 45 PSIG

4. 50 PSIG

The correct answer is: 33.3 PSIG

To determine the pressure of oil in a discharge pipe at ground level, we can use the height of the oil column above the discharge point and the density of the oil to calculate the pressure. In this case, the tank is filled with #6 oil, which has an approximate density of 7.5 lb/gal. Since the tank is 110 feet high and 70% full, we first calculate the effective height of the oil: Effective height = 110 feet x 70% = 77 feet. The pressure exerted by a fluid column can be calculated using the following formula: Pressure (in psi) = (Height of the fluid column in feet) x (Density of the fluid in lb/ft³) / 144 (to convert from lb/ft² to psi). To convert the density from lb/gal to lb/ft³, we use the conversion factor where 1 gallon = 0.133681 cubic feet. Therefore, the density of #6 oil in lb/ft³ is: Density = 7.5 lb/gal / 0.133681 ft³/gal ≈ 56.105 lb/ft³. Now we convert the height of the oil column from feet to