Spring 99 Vol. 2 No.1
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From the Director: Steam Kettles !
The design of the steam kettle makes heating and cooking very efficient and fast. If we look at the typical kettle, the sight is always familiar: a large container with a round or spherical bottom, reminiscent of the old cauldron. Kettles have a double wall or "jacket" covering the bottom and at least half the height of the sides, to provide space for the steam to circulate and therefore to heat the cooking surface. The use of the steam as the heating medium has many advantages: uniform heating, fast heat transfer and easy control of the heating rate through a steam valve. The steam can be supplied to the kettle by an independent boiler through a pressurized pipe or it can be produced in-situ for immediate use, as is the case in the so-called "self-contained steam kettles". Self-contained kettles heat water with electric energy (electric steam kettles) or with gas (gas fired steam kettles) to generate the steam under pressure. The temperature of the steam is dependent on the pressure inside the steam jacket, the higher the pressure the higher the temperature. Most kettles are rated at 50 psi as the maximum pressure although some are rated lower to about 35 psi. In large food companies where boilers are standard equipment, direct steam kettles are normally preferred while small processing plants that do not have boilers can rely on self-contained kettles. A wide variety of sizes and options complement the choices: from 0.5 gallons to 200+ gallons, one piece (lift-off) or two piece covers, tilting capability, draining valves in different types and sizes, strainers, baskets, agitators and vacuum or pressurized models for custom applications.
New steam kettles range in price depending on size, type and options starting at about $3,000 for very small direct steam models and up to $20,000+ for the larger versions. It is possible to get a used kettle in good condition for a fraction of the original cost from most dealers of used food processing equipment or food service distributors. A list of suppliers can be found on page 5.
References Imholte, T.J. 1984. Engineering for food safety and sanitation-a guide to the sanitary design of food plants and food plant equipment. Technical Institute of Food Safety, Minnesota, USA.
by Olga Padilla-Zakour
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One
of the most used food equipment pieces in small scale processing is the
steam kettle. It is also common in restaurants and large institutional
kitchens.
Virtually
all food steam kettles are made of stainless steel, a trade name given
to corrosion resistant steel, and the number one choice material for construction
of food equipment. Normally stainless steel contains no more than 0.7
% carbon and as much as 20 % chromium. There are two types of stainless
steel commonly used for steam kettles: 304 and 316. The numbers designate
the chemical composition of the material describing the percentage of
steel (66.5 to 74 %), chromium (17 to 19 %), nickel (9 to 12 %) carbon
(0.03 to 0.10 %) and molybdenum (0 to 2.5 %). Stainless steel 304 is the
standard option but if you are working with high acid and acidified foods
it pays to specify 316 as it offers more resistance to hot acid foods
for a relatively modest price increment.