Nuts in steam bolting must be American Standard heavy ______ ______?

The correct choice highlights the requirement for steam bolting nuts to be American Standard heavy hexagonal semifinished. This is significant because heavy hexagonal nuts are specifically designed for use in high-pressure applications like steam systems, where strength and reliability are paramount.

Heavy hexagonal nuts feature an increased thickness and width compared to regular hex nuts, offering greater load-bearing capabilities. The semifinished designation indicates that these nuts are not fully machined but are provided with a sufficient finish to ensure they meet the necessary specifications for threading and strength. This is essential in applications where there are extreme pressures and temperatures, ensuring that the fasteners maintain their integrity and perform safely.

Using nuts that do not meet these specifications can pose serious risks, as they may fail under high pressure, leading to potential accidents or system failures. Therefore, selecting heavy hexagonal semifinished nuts is a crucial aspect of safe and effective piping system design in high-pressure steam applications.