A wrought iron pipe schedule of 40 can withstand a steam pressure up to what level?

Wrought iron pipes, particularly those categorized under schedule 40, are designed with certain pressure ratings that indicate the maximum pressure they can safely handle. The pressure rating for schedule 40 pipes, specifically in the context of steam, is generally known to be around 300 psi. This level takes into account the material properties of wrought iron, the pipe's dimensions, and the standard safety factors applicable in steam applications.

Understanding that pressure ratings can vary based on temperature and specific application guidelines is crucial. However, for schedule 40 wrought iron pipes, the maximum rating for steam service typically does not exceed this 300 psi threshold, making it the appropriate choice for the question asked.

The other options, notably 200 psi, 400 psi, and 500 psi, do not accurately reflect the common pressure capacity of schedule 40 wrought iron pipes for steam. Thus, 300 psi stands out as the correct and widely accepted rating for this specific application of wrought iron piping.