When more than 2 high pressure safety valves of different sizes are mounted on a boiler, the relieving capacity of the smaller valve should not be less than what percentage of that of the larger valve?

The correct answer is based on the guidelines for the relieving capacity of safety valves in high-pressure applications, including boilers. When multiple safety valves of different sizes are used, particularly in boilers where high pressure is a concern, the smaller safety valves must have a specific capacity relative to the larger valves to ensure adequate pressure relief.

In practice, the smaller safety valve should have a relieving capacity of not less than 50% of that of the larger valve. This requirement ensures that, in the event of a pressure increase, the smaller valve can still provide significant relief, therefore helping to prevent overpressure situations effectively. If the smaller valve's capacity were to drop below this 50% threshold, it would not provide sufficient backup protection, potentially leading to unsafe pressure levels within the boiler system.

This requirement is part of safety standards aimed at maintaining operational safety and efficiency in high-pressure systems, guiding engineers and technicians in their selection and installation of safety valves. Adhering to this guideline is essential for ensuring reliability and safety in the boiler operation.