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What Is the Difference Between a Steam Jacketed Kettle & a Trunnion Kettle?

Herb Kirchhoff

A steam jacketed kettle is a cooking appliance used in institutional and military kitchens that must prepare large quantities of food at one time. A trunnion kettle is a type of steam jacketed kettle mounted on pivots called trunnions that allow the entire kettle to be tilted to pour the contents out into serving utensils. Trunnion kettles usually have a pouring lip, and they are counterbalanced to easily be tilted by manual wheel or lever.

Steam Kettle Basics

Steam jacketed kettles are an improved version of the old stockpot used in range-top cooking. Stationary and trunnion steam kettles cook all types of liquid and semi-liquid foodstuffs or boil solid foodstuffs. Steam kettles are enclosed by an outer wall, or jacket, into which live steam is introduced. The steam jacket extends halfway to two-thirds of the way up the kettle. Steam kettles cook by conduction. As the steam condenses into water, it passes its heat through the kettle’s inner wall directly into the food. Steam kettles operate at pressures of up to 50 pounds per square inch and have safety valves to let off excess steam pressure. They produce temperatures between 212 and 300 degrees Fahrenheit, depending on steam pressure.

Kettle Advantages

Steam kettles provide a much larger hot surface than stock pots, which are only heated on the bottom. Steam kettles, by contrast, are heated on the bottom and sides by the live steam. Because steam kettles heat evenly without hot spots that can scorch food, they lend themselves to unattended automated cooking of soups and sauces. Trunnion kettles are commonly used to reheat prepared prepackaged foods and for simmering items such as chili that require long, slow cooking.

Many Models

Stationary and trunnion steam kettles are produced by a number of different manufacturers. They are made of stainless steel for table, floor or wall mounting. Tilting trunnion kettles typically are under 60 gallons while stationary steam kettles can exceed 200 gallons. Stationary kettles have spigots at the bottom to drain out their contents. Steam kettles use pressure sensors or thermostats to control steam cycling and maintain temperature. Steam kettles with integrated boilers can be heated with electricity or gas. Other models can be heated with steam from an external boiler.


Makers of steam jacketed kettle offer accessories. Electric mixers are a popular option because they allow foods to be stirred and blended without constant human attention. With mixers, a single cook can tend to several kettles at once. Most kettles over 80 gallons come equipped with electric mixers. Kettles can have accessory racks for steaming several different foods in the same vessel. Lids are another kettle option.