Screw Plug Immersion Heaters

Screw Plug Immersion Heaters
Screw plug immersion heaters are ideal for direct immersionheating of liquids, including all types of oils and heat transfer solutions.

Available in a variety 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 element sheath
and plug material compatibility.

General purpose terminal enclosures are standard; with optional moisture resistant, explosion resistant and explosion/moisture resistant enclosures available to meet specific application needs.

Optional thermostats provide convenient process temperature regulation.

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Product Features

A variety of element sheath and screw plug materials
  • Meets a variety of application needs
Integral thermowells
  • Provides convenient temperature sensor insertion and replacement without draining the fluid being heated
Terminal enclosures
  • Provides ability to be rotated to simplify connection with existing conduits
Welding or brazing WATROD and FIREBAR elements to the screw plug
  • Provides a pressure tight seal
WATROD hairpins are repressed (recompacted)
  • Maintains magnesium oxide density, dielectric strength, heat transfer and life
21/2 in. (64 mm) NPT screw plug assemblies feature element support(s)
  • Ensures proper spacing for maximizing heaterperformance and life

Product Specifications

Wattages up to 38 kilowatts
Watt Density:
Watt densities up to 120 W/in2 (18.6 W/cm2)
Sheath Materials:
  • Alloy 800/840
  • Stainless Steel
Sheath Temperature:
  • Alloy 800/840 sheath temperatures up 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)
Agency Approvals:
  • UL® and CSA component recognition up to 480VAC and
  • 600VAC respectively


  • Water: Deionized, Demineralized, Clean, Potable, Process
  • Industrial water rinse tanks
  • Vapor degreasers
  • Hydraulic oil, crude, asphalt
  • Lubricating oils at API specified watt densities
  • Air and gas flow
  • Caustic solutions
  • Chemical baths
  • Anti-freeze (glycol) solutions
  • Paraffin