Kunkle Takes The Pressure Off

Kunkle Takes The Pressure Off

Kunkle Valve. It’s fun to say, isn’t it? But while the name may sound like the noise a wrench makes when you drop it into a barrel of water, the truth is, Kunkle valves are music to the ears of anyone who wants to operate a boiler safely. That’s because they help protect boilers from operating at too high of a pressure.


Way back in 1875, a machinist and inventor named Erastus Kunkle found himself working for the Pennsylvania Railroad. One of the biggest problems he was trying to solve was the issue of overpressure in steam locomotives. Since locomotives used steam pressure to move the pistons that moved the wheels, pressure was a necessity. However, if there was too much pressure in the locomotive’s pressure vessel, catastrophic things could happen. Rivets could pop out and go flying like bullets. Metal could rupture and crack, spraying steam everywhere. In the worst cases, a sudden failure would result in an explosion that would destroy the engine and cause serious harm to those in the immediate vicinity. Needless to say, keeping pressure within a safe margin was a necessity. Proper operation required the engineer to closely monitor pressure gauges to keep steam production in balance with what the locomotive needed to maintain the desired speed. However, gauges can fail, and people can make mistakes. What Kunkle needed, therefore, was a way to automatically release the steam pressure if it went too high, before a rupture or explosion could occur. The valve he invented was designed to open at a certain pressure, one that was below the physical limits of the boiler vessel, so excess pressure would automatically release into the atmosphere before it could cause any damage or ruptures.


Boilers are like locomotives in that pressure is necessary for proper operation. Without it, the temperature of the steam wouldn’t be able to go above 212°F. In fact, that pressure is what makes steam one of the world’s most efficient ways to move heat; the higher the pressure, the more heat the steam can hold, and the more work it can do at the end process. As you can see, then, pressure is a great thing to have. But you don’t want too much of it.Boilers are made of metal, and metal has limits to the stress and strain it can endure. Push the metal past its breaking point, and it will… well, it will break. If that happens in a boiler, you’ll end up with a costly failure that will translate to lost work and down time. That’s where the Kunkle valve comes in. 


The design of a Kunkle valve is fairly simple, which is one of the reasons why they are so reliable. Inside a Kunkle valve, you’ll find a vent nozzle that has a disc seated in it. That disc is held in place by a spring of a specific strength. As long as the pressure pressing on the disc remains below the strength of the spring, the valve will remain closed. However, if the pressure gets high enough that it overpowers the spring, the disc will move back and let pressurized steam escape past, and vent out the nozzle. Because they’re so simple and rugged in their design, Kunkle valves are more than just durable and reliable, they’re also appropriate for a wide range of materials and temperatures, as well. They can maintain pressure in water, air, steam, and other gases at temperatures that range from well below freezing to over 800°F. 


While Erastus Kunkle’s pressure relief valve is a massive accomplishment that made boiler operation safer for everyone, he contributed even more to the world. He was also the inventor of the boiler water gauge and the gauge cock, both of which help boiler operators prevent lost steam production and boiler damage due to low water levels. He also gave the world an improved version of the eggbeater, as well. So you can thank him for safe boiler operation, and for great omelets and scrambled eggs. 

If you’re in need of a new Kunkle pressure relief valve, WARE’s online Boiler Warehouse stocks a full line of them for all boiler makes and models. We also have experienced technicians to install and maintain them, as well. Whatever you need, from new or rental boilers to boiler service to boiler training online or in-person, WARE has you covered. We’re here to help.

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