The defense industry uses precise heating equipment for many applications. Fuel preheating processes as well as pressure heaters use Wattco flanged heating elements within their delicate processes.The flexibility of these immersion heater types include the ability to select the exact type of flange required, fittings as well as desired lengths that meet tank requirements. Flanged heaters are CSA and UL approved to meet industrial guidelines. Recirculation heaters for the military (http://www.wattco.com/blog/?p=212) are used in conjunction with demineralized water storage tanks to help with the  process and heating control requirements. The inline heaters are available in a wide range of wattages, flanged fittings, threaded terminals, alloys as well as vessel sizes and terminal enclosures to meet the most stringent design requirements. Large tanks with 300,000 GAL of liquid or more often utilize Wattco pipe heaters in their designs that offer ease of maintenance as maintenance of heaters do not require emptying the contents of the tanks. Wattco pipe heaters are inserted in (ie.) 3 inch SCH40 pipes that are not in contact with the liquid. NEMA 4 housing ensures terminal protection and a gradual heat is used along the length of the tank. Coiled elements are standard however for environments of high vibration, tubular elements can also be used achieving extremely favorable results.