What Do Safety Valve Tags Mean? HV vs V vs UV Explained

Not all safety valves are approved for the same job. In this Weekly Boiler Tip, we break down the markings found on a boiler safety valve and explain what they actually mean. While set pressure and capacity are easy to spot, the stamped labels on the valve are just as important because they tell you what application the valve is approved for. We cover the meaning behind NB, HV, V, and UV safety valve markings, plus the key exception that trips people up in the field. If you work on steam boilers, hot water boilers, or pressure vessels, knowing these markings matters. Safety notice: Always consult experts for complex repairs. Weekly Boiler Tips are compiled by the knowledgeable and remarkably prolific content creators at WARE, a family owned, third-generation, 69-year-old commercial and industrial boiler rental and service firm based in Louisville KY. You can learn all about this and more at WARE's Boiler University.