New York Low Pressure Boiler COF Practice

What is the maximum allowable safety valve blowdown percentage of the set pressure?

1. 5%

2. 4%

3. 2%

4. 3%

The correct answer is: 2%

The maximum allowable safety valve blowdown percentage of the set pressure is defined as the difference between the pressure at which the valve opens and the pressure at which it reseats. A blowdown percentage of 2% is standard for low-pressure boilers, as it ensures that the system remains safe and efficient during operation. This specific percentage helps maintain a balance: it is low enough to prevent leakage of steam or pressure loss when the system is operating, and high enough to ensure that the safety valve operates effectively within its design limits. When safety valves have excessive blowdown, it can lead to instability in the pressure control, and if it is too low, it may not provide adequate safety margins. In the context of the other choices, they suggest higher blowdown percentages, which would not be compliant with standard safety practices for low-pressure boilers. Therefore, adhering to a blowdown percentage of 2% is crucial for optimal safety and operation.