WATTCO SCREW PLUG HEATERS
Screw plug heaters are immersion heaters traditionally used in kitchen heating, chemical processing and waste oil applications. Wattco screw plug heaters are water heating elements and range in size from one inch to 4 inches, in standard NPT (National Pipe Thread) or in certain special applications NPS (National Pipe Straight). The key difference between the two thread styles is that NPT, because the threads are tapered, the male screws into and jams against the female fitting, thereby creating the seal. In addition, pipe tape or different pipe joint compounds can be used to further seal the threads against leakage. NPS threads do not taper, and the seal is made through a gasket or O-ring that is sandwiched between the flange boss of the fitting and the female fitting that it is being screwed into. Material of NPT fittings can be provided in steel, brass, or stainless steel, depending on tank material or the material being heated (ie. Waste Oil Heaters typically use steel).

This is done to reduce galvanic reactions between unlike metals and also to reduce or prevent reactions with the material being heated. Tubular elements are arranged on the fitting for the best possible heat dispersion. A thermowell can also be installed into the element array to a sealed enclosure to install a temperature probe or sensing device. The elements can be silver brazed or TIG welded to the NPT fitting to ensure a leak-proof seal.

Terminal enclosures can be constructed for various needs including NEMA 1 (standard housing), NEMA 4 (moisture resistant) used in Oil Heaters and NEMA 7 (explosion proof). Regular thermostats or pilot duty thermostats can also be fitted within the terminal enclosure.

Immersion heaters such as screw plug heaters are used anywhere there are special limitations or the tank wall does not permit the installation of a flange heater. Pipe heaters can use screw plug heaters because they offer efficient compact heat characteristics. Screw plug heaters are lightweight, can be installed horizontally or vertically and very versatile. They can also be used in small circulation heaters (in line heaters), where space constraints preclude the use of larger, flanged heater circulation heaters.