Product Knowledge Guide: Steam-Jacketed Kettles

Steam-jacketed kettles have been used in food preparation for more than a 100 years. Typically foodservice operators use these appliances to produce stocks, sauces, soups and fillings in large quantities. These pressurized stainless steel vessels utilize steam energy to transfer heat via conduction to the food product inside.

Steam-jacketed kettles come in three basic categories defined by the energy source that operates the kettle: electric, gas and direct steam. Direct-steam kettles offer greater efficiency, cooking the fastest with the highest capacity as compared with electric and gas models.

This category further breaks down by the style and size of the kettle, which includes stationary floor models (typically 20 gallons and up in capacity), tilting floor models (typically 20 to 200 gallons in capacity) and tabletop kettles (ranging from 1 quart to 12 gallons in capacity).

Generally speaking, the operating pressures of these kettles range from 45 PSI to 50 PSI, producing an even temperature of 267 degrees F to 338 degrees F for the entire jacketed surface. Although these temperatures are not as hot as an open flame on a range, they still cook at a very fast rate due to the equipment's increased surface area that transfers the energy.

The majority of kettles are two-thirds jacketed, which means that the heat energy transfers not only from the bottom of the kettle, like in a stock pot on a range, but also from the sides of the kettle. This increases the surface area for energy absorption into the product dramatically. Fully-jacketed kettles also are available.

Common Applications

  • Foodservice operators use steam-jacketed kettles in a multitude of ways, including, delicate sauces, stocks, pasta, gravies, desserts, stews.

Specifying Considerations

  • Determine the products and batch sizes that staff will prepare in the steam-jacketed kettle.
  • Because these units tend to be large, space availability represents a consideration.
  • Determine the available fuel or power source, such as gas or electric.
  • Confirm the floor drain and trough location, and water availability for filling and cleaning.
  • Decide if a tilting or stationary kettle would work best in the operation.

Specifying Mistakes to Avoid

  • One common mistake is not ordering a tangent draw-off valve. Because they can't be installed in the field, some manufacturers will send a sign-off sheet if the operator does not order the valve to confirm this is what's needed.
  • Operators typically neglect to measure the space from the floor to the hood, which will verify that staff can raise the kettle during operation.

When to Replace

  • Leaking: If the kettle's compound gauge is not in the "green zone" in the morning when cool, this could indicate a leak in kettle somewhere. There also could be visible leaking from the kettle's jacket area.
  • Material breakdown: Inner liner pitting and/or external stress fissures may indicate the kettle has reached the end of its service life.

Maintenance Musts

  • Proper daily cleaning is important for a long service life.
  • Use only non-caustic cleaners. Refrain from using chloride detergents, steel pads, wire brushes or scrapers on kettles.
  • Lubricate the trunnion bearing on a regular basis.
  • Test the pressure relief valve every six months to ensure proper operation.
  • Replenish internal hemi water with distilled water and liqua-phase rust inhibitor or equivalent product when required.
  • Change steam seals on direct-steam kettles once a year or as required by use.

Editor's Note: FE&S thanks Mike Dyekman, CFSP, of Webb Foodservice Design for his help with this article.

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