What is the correct rule of thumb formula for the ultimate strength (US) of wire rope?

The correct rule of thumb formula for determining the ultimate strength (US) of wire rope is given by the formula US = d² x 45, where "d" represents the diameter of the wire rope in inches. This formula is widely accepted in the industry as it provides an approximation of the tensile strength based on the cross-sectional area of the rope.

Using the diameter squared (d²) in the formula accounts for how the strength of a wire rope increases with its cross-sectional area, which is proportional to the square of its diameter. The factor of 45 in the equation represents a general estimate of the strength per unit area of the wire rope material, making it a practical method for quick calculations in the field.

This insight is vital for steamfitters and related trades, as it helps them to make informed decisions when selecting wire rope for lifting and rigging applications, ensuring safety and effectiveness. Understanding how to derive ultimate strength using this formula is crucial for proper equipment selection and application in real-world situations.