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Weather may be unpredictable, but seasons and climate are inevitable. Manufacturers and utilities in cold and moderate climates around the world must be prepared for when the mercury in the thermometer drops and their process liquids or raw materials are at risk of freezing or gelling.

Although water freezes at 0° C, viscosity and crystallization changes can begin to occur above freezing. This critical challenge can result in wasted material and time, and even equipment damage and facility shutdown if manufacturers aren’t proactive about keeping their liquid materials or feedstock flowing. This is a major issue in the oil and gas, food and beverage, freight transportation, chemical processing and water utilities industries, just to name a few.

The most efficient and adaptable solution to prevent tank and reservoir freezing is the immersion heater. For these applications, flanged and circulation-type immersion heaters are recommended. These are highly durable devices that are resilient to challenging environments and corrosives. Since the heating elements of an immersion heater are in direct contact with the process fluid, they are quite efficient.

Figure 1. Depictions of a flanged immersion heater (top) and a circulation immersion heater (bottom). Source: WattCoFlanged immersion heaters are installed via an ANSI-rated flange in the sidewall of a tank or storage vessel—the tubular heating elements surrounding a thermowell sensor extend into the liquid while the element terminals, power supply and a digital, programmable interface are housed in an external NEMA-rated enclosure. Flanged heaters are suitable for pressurized tanks and are widely used in the oil industry, as well as in chemical and water applications. These heaters can maintain the temperature of the fluid in the tank with a thermostat and a high-limit switch prevents overheating.

Circulation or inline heaters draw from the storage tank and heat the fluid in a separate heating unit, where the fluid is warmed in a chamber containing one or more flange heaters or a screw plug heater. From there, the fluid—commonly oil, water, viscous materials, gases or solvents—is directed back into the storage tank or to another processing step. Tank insulation is a key to thermal retention within the tank. Circulation heaters are highly adaptable to many storage vessels and tanks, and can also be skid-mounted for temporary installation. A drain valve is an additional benefit to this type of heater, as it facilitates easy access to the heating elements for cleaning and maintenance.

Immersion heaters are highly-engineered equipment; many of the heater’s specifications are purpose-built for the application at hand.

• Materials: The application and corrosiveness of the fluid must be accounted for during materials selection (see figure 2).
• Temperature: Concerns include the temperature set point and tolerance, temperature controls and how quickly the heater can raise fluid from ambient to target temperature. This parameter can influence power density, component selection, number of heaters and materials.
• Safety: Applications may have critical safety considerations, such as sterility in food and beverage applications, or the control panel’s resistance to weather, water and fire.
• Power density: The wattage of the immersion heater to provide sufficient fluid heating without deteriorating fluid quality. High-power heaters may utilize more heating elements.
• Budget: Selecting an economical immersion heater without sacrificing features or device reliability.

Immersion heaters aren’t overly complicated, but they are in fact crucial pieces of equipment in so many industries. Because they offer high customizability, it is important to enlist the help of an experienced manufacturer early in the selection or tank design process.

To keep your fluids and productivity flowing with immersion heaters, visit WATTCO online today, or call 800-492-8826.