Screw Plug Immersion Heaters

screw plug immersion heaterScrew plug immersion heaters are a specific type of immersion heater ideal for direct immersion heating of various liquids, including all types of oils and solutions involving the transfer of heat.

Available in a wide assortment of sizes, Watlow® screw plug immersion heaters feature both WATROD™ round and FIREBAR® flat tubular elements.

Heating elements are hairpin bent and either welded or brazed into the screw plug — depending on the elements particular sheath and plug material compatibility. General purpose terminal enclosures are standard; with optional moisture resistant, explosion resistant and dual explosion/moisture resistant enclosures available to meet the individual’s specific application needs. Optional thermostats provide convenient and easy process temperature regulation to the screw plug immersion heater.

In addition to screw plug immersion heaters, Hi-Watt Inc. carries a wide variety of other types of immersion heaters including over the side immersion heaters, and flanged immersion heaters. Contact us today for more information on industrial heaters and how we can help you.


Material Maximum Opening Temperatures Maximum Watt Densities
°F °C W/in² W/cm²
Alloy 800/840 1600 870 120 18.6
Stainless Steel 1200 650 120 18.6
Steel 750 400 120 18.6
N/A 350 175 120 18.6
Features & Benefits:
A wide variety of element sheath and screw plug materials
  • Meets a wide variety of application needs unique to your situation
Integral thermowells
  • Provides convenient and easy temperature sensor insertion and replacement without needing to drain the fluid being heated
Terminal enclosures
  • Provides the convenient ability to be rotated to simplify it’s connection with existing conduits
Welding or brazing WATROD and FIREBAR elements to the screw plug
  • Provides a leak free pressure tight seal
WATROD hairpins are repressed (recompacted)
  • Maintains MgO density, dielectric strength, heat transfer and life duration
2 ½ in. (64mm) NPT screw plug assemblies feature element support(s)
  • Ensures proper spacing for maximizing the heater’s performance and life
  • Watt densities to 120 W/in² (18.6 W/cm²)
  • Wattages to 38 kilowatts
  • UL® and CSA component recognition to 480VAC and 600VAC respectively
  • Alloy 800/840 sheath temperatures to 1600°F (870°C)
  • Passivated 316 stainless steel sheath temperatures up to 1200°F (650°C)
  • 304 stainless steel sheath temperatures up to 1200°F (650°C)
  • Steel sheath temperatures up to 750°F (400°C)


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