Which of the following characteristics is essential for safety valves?

A safety valve's primary function is to protect systems from overpressure by opening at a predetermined pressure and allowing excess pressure to be released. The characteristic that it must open fully and quickly at set pressure is crucial because this rapid response prevents catastrophic failure or damage to the equipment or surrounding areas. If a safety valve fails to open promptly or does not open all the way, it can lead to an unsafe buildup of pressure, possibly resulting in an explosion or severe equipment damage.

Safety valves are designed to operate automatically without manual intervention, making manual operation unnecessary and impractical for their intended purpose. They are also applicable to various pressure systems, not just high-pressure ones, as many systems need the assurance of pressure relief regardless of their pressure classification. Adjustability is not an essential feature; it is critical that the valve opens consistently at the designated pressure instead.