Minnesota Boiler License Practice Exam

What is the maximum pressure difference allowed for a safety relief valve designed for pressure above 250 lbs P.S.I.?

1. 2% above or 2%

2. 5% above or 5%

3. 6% above or 6%

4. 10% above or 10%

The correct answer is: 5% above or 5%

The correct maximum pressure difference allowed for a safety relief valve designed for pressures above 250 lbs P.S.I. is 5% above or 5%. This standard is critical because safety relief valves are designed to prevent overpressure conditions that could lead to a boiler or pressure vessel failure. The specified tolerance ensures that the valve can accurately release pressure before reaching a dangerous level, thus maintaining system safety. A 5% variation allows for slight inaccuracies in the set pressure without compromising the safety function of the valve. This value is commonly accepted in the industry to balance safety with operational reliability. The higher tolerances provided in other options could possibly lead to situations where the safety relief valve might not activate in time to protect against overpressure scenarios, thus increasing the risk of accidents or equipment damage. Therefore, adherence to the 5% maximum pressure difference is critical in ensuring the effectiveness of safety devices in high-pressure systems.