Which is true about safety valves discharging into a common outlet pipe?

The statement that the outlet pipe diameter must equal the sum of the discharge outlets is correct because it ensures that the outlet pipe can handle the combined flow from all safety valves discharging into it. Safety valves are essential in maintaining system pressure and preventing overpressure situations, and if multiple valves open simultaneously, the discharge capacity of the outlet pipe must be adequate to accommodate the total volume of steam or fluid being released. If the diameter of the outlet pipe is too small, it can lead to excessive backpressure, which may compromise the safety function of the valves or even cause damage to the system.

This requirement is critical in designing safety systems because it helps to ensure that all safety mechanisms work effectively without risk of creating a bottleneck or pressure buildup that could lead to equipment failure or safety hazards. Proper sizing of the outlet pipe based on the cumulative discharge from all connected valves is a fundamental principle in engineering design to maintain safe operating conditions.