When the discharge pipe of a safety valve extends through the roof, it must extend above the roof by how many feet?

The requirement for the discharge pipe of a safety valve to extend above the roof a specified distance is rooted in safety and effective operation. Extending the discharge pipe at least 7 feet above the roof serves multiple purposes.

Primarily, this height helps ensure that steam or other discharge from the safety valve does not present a hazard to personnel or equipment on the roof or nearby areas. By directing the discharge safely into the atmosphere at a sufficient height, it minimizes the risk of exposure to hot or potentially harmful vapors that could affect those working or moving around the facility.

Additionally, this height can help prevent the accumulation of fluids or condensation that might occur if the discharge pipe is too low, which can further mitigate risks related to performance and function of the safety relief devices. Raising the discharge pipe also aids in effective dispersion of gases, which is crucial for maintaining a safe and environmentally compliant operation.

The other options of 3, 5, and 6 feet do not meet the established safety standards as thoroughly as the 7-foot requirement, which is why this is the correct choice in ensuring optimal safety measures are in place.