According to Coast Guard Regulations (46 CFR), which of the following steam piping conditions, subjected to main boiler pressure, is exempted from hydrostatic testing?

Correct Answer: Option B — All piping with a nominal size of 3 inches or less.

Under 46 CFR Subchapter F, certain small-diameter piping systems are exempt from mandatory hydrostatic testing due to their inherent structural strength. Specifically, piping with a nominal size of 3 inches or less subjected to main boiler pressure does not require individual hydrostatic testing.