Pipe thread heaters are heaters that have a hex that screws into a threaded pipe. The heating element bends in a repressed and uniform fashion to ensure electrical insulation integrity. Some of the elements also have a one-piece forging of a hex, thread, and riser. With all of this being one-piece, it creates more reliability. To prevent hot spots, many of the heating elements will have element spacers. With this being screwed into a pipe, it is essential to create a seal to ensure optimal performance. This can be done by having an epoxy seal.
Tubular Elements are welded into a hex head pipe thread fitting. Elements have 80/20 nickel-chromium resistance coils centered in a heavy gauge metal tube surrounded by magnesium oxide insulation. Through rolling, the magnesium oxide is compacted for rapid heat transfer from the coil to the sheath. The elements are annealed, bent, and then 360 degrees repressed to ensure magnesium oxide integrity in the bent area.
1” and 1.25” pipe thread heaters have .312” diameter elements for operation up to 277 volts. 2” and 2.5” pipe thread heaters have .475” diameter elements suitable for operation up to 600 volts.
Pipe Thread Fittings
Pipe Thread fittings of forged brass, silver soldered to the sheath, are furnished as standard with copper sheathed heaters. Steel and stainless steel sheathed elements are welded into fittings of related material.
Outlet Boxes are furnished on heaters without a built-in thermostat. A 4” NEMA 1 octagon outlet box having ¾” knockouts is standard. 2” NPT stock heaters (without thermostats) are furnished with cast liquid-proof outlet boxes.
Heaters with a built-in thermostat usually are furnished with a NEMA 1 rectangular sheet-metal enclosure having combination ½” to ¾” knockouts. Heaters drawing more than 40 amps are equipped with welded steel outlet boxes having 1” or 1.25” hubs for electrical connections.
A built-in Thermostats allows for automatic temperature control without needing to installing a separate well for the thermostat bulb in the field. This allows making electrical connections between the heater and control. A standard thermostat is a single-pole for single-phase heaters, for pilot duty three-phase applications, and two poles for de-energizing load carrying applications. Any heaters that are rated above these capacities may need a magnetic contactor, with a thermostat controlling the contactor holding coil.