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Circulation Heaters also known as "in line heaters" use steel, stainless steel, titanium flanged immersion heaters in many applications. Lube oil and waste oil applications often use steel for circulation heaters as it is fairly inexpensive compared to stainless steel counterpart. In line heaters flowing water use stainless steel, admired for its anti corrosive qualities. Both applications involve using a pump that flows the liquid through a closed pipe circuit (IE. water or glycol solution) that is reheated. A major consideration for this application is viscosity. Heat that is generated by the oil heater allows the liquid to be viscous enough to pass through the circuit of pipes. Circulation heaters come in a range of watt densities that are specifically designed for the medium that is heated. The required wattage to heat the oil or water is highly correlated to the flow rate (in GPM). The oil or water enters through an inlet (the inlet closest to the flange heater) and gets heat applied to it as it flows within a vessel chamber and exits the outlet nozzle (or flange) where it circulates throughout the piping circuit. Insulation is often required for vessels in order to preserve the heat to be applied within the vessel. Efficient heat application can often reduce unnecessary costs through heat loss. Digital thermocouple probes or RTDs, can be  used with the electric immersion heater to maintain the oil or water at the preferred temperature. Many applications use liquids with low flash point and, require explosion proof housing (NEMA 7) to avoid potential mishaps.
 

In-line heaters that are fabricated using steel are often used with oil based applications. The majority of these circulation heaters are used in conjunction with a digital control panel and a probe that is positioned either in the bundle of elements or, alternatively at the outlet (exit) of the vessel. In line heaters are a useful way of heating up your medium without altering the container you are using. In line heaters are also considered safe alternatives to heating liquids directly in the tank. Maintenance ease and the ability to modularize each in line heater allows for excellent redundancy system in case of shutdown.
 

Other useful features found with circulation heaters are drain valves.  They can be installed in any location on the vessel and allow for easy maintenance of the heater. The water or oil can be purged through the drain valve allowing for maintenance on the elements. Calcium deposits and other residue can be found on elements and should be cleaned several times a month. Inline heaters also come with the choice of horizontal or vertical mounting depending on your application. Skid mounted vessels are used in oil heating industries that require mobility. Wattco heaters are also available in moisture resistant terminal boxes or explosion proof terminal boxes for hazardous environments. Wattco in line heaters are an exceptional choice for heating process liquids, non corrosive to the materials of construction. In line gas heaters are also used when heating closed loop systems that require high temperatures of up to 1000 deg F. These applications use large flanged vessels that contain the gas and heat it up in containment most efficiently requiring low maintenance and excellent heat transfer.