If a high pressure boiler operates at 100 psig, what should the blowback of the safety valve be?

In boiler safety systems, the blowback of the safety valve—also known as blowdown—is an important parameter that helps to ensure the valve functions correctly under operational conditions. For a high-pressure boiler operating at 100 psig, regulations usually dictate an acceptable blowback range.

The accepted practice sets the blowback limits to not more than 4% of the set pressure and not less than a certain minimum pressure. In this context, with a set pressure of 100 psig, 4% equates to 4 psig, leading to a minimum allowable blowback of 2 psig. This framework ensures that the safety valve remains responsive and opens at the appropriate pressure, allowing for safe operation while accommodating small fluctuations in system pressure.

Option A’s specification reflects these safety standards accurately, setting limits that effectively maintain the integrity of the safety device and ensure proper functioning to prevent excessive pressure in the boiler. In contrast, the other options either set inappropriate percentage limits or minimum psig values that do not align with established safety regulations for a high-pressure boiler setup, thus failing to ensure the necessary operational reliability and safety.