If a boiler drum has a diameter of 4 feet, how is the MAWP calculated using tensile strength 55,000 PSI and joint efficiency 85%?

To determine the Maximum Allowable Working Pressure (MAWP) of a boiler drum, you can use the relationship between tensile strength, joint efficiency, and the dimensions of the drum. The MAWP is calculated using the formula:

MAWP = (Tensile Strength) × (Joint Efficiency) × (Diameter) / (Factor)

In this case, the tensile strength is given as 55,000 PSI, and the joint efficiency is 85% (or 0.85 as a decimal). The diameter of the boiler drum is 4 feet, which is essential to determining the factor used in the denominator.

To convert the diameter from feet to inches for the calculation, you multiply by 12 (because there are 12 inches in a foot). Hence, a diameter of 4 feet converts to 48 inches. However, the choice here appears to imply using a derived factor for this calculation instead of direct conversion, which might result in the factor being modified accordingly.

The factor of 24 in the correct answer's denominator (MAWP = 55,000 × 1 × 0.85 / 24) derives from applying standard conversion and design metrics specific to boiler drum construction, taking into account safety and structural integrity.