Screw Plug Heater

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Screw Plug Heaters are smaller versions of Immersion Heaters in which the heater flange is replaced with a Threaded Plug. A Single or multiple tubular heating elements that fit into a thread hexagonal head are then screwed directly through a threaded coupling in the tank wall or vessel or installed process line. Screw plug heaters are an easy way to heat up solutions in smaller containers that may or may not require auto control on temperature. The Heaters can be installed either horizontally or vertically in the tank. The heater is compatible with both Single-phase as well as three-phase power supplies.

The screw plug heaters are also be provided with a Thermowell, in which a temperature sensor can be installed for the Temperature monitoring and control purpose. In most of the applications, a simple thermostat will be installed inside the thermowell and pre-wired with the installed heater to ensure the heater is ON / OFF at a pre-set temperature. The Thermostat knob can be projected outside the terminal cover for easy access of the operator.

Key Features

  • Efficient Heating and operation
  • Easy to install
  • Maintenance-friendly
  • No expensive
  • Environmental performance
  • Sheath Material

    SS, Alloy 600 series, Alloy 800 series, Hastelloy, Titanium, copper, etc

  • Power Rating

    0.1kW to 50kW

  • Screw Plug Material

    CI, Carbon steel, Brass, SS, etc

  • Screw Plug NPT fittings

    1”, 1.1/4”, 1.1/2”,2”,2.1/2”, 3” (BSP/ NPT) or equivalent Metric threads

  • Voltage

    120 to 690V AC Single phase or three-phase

  • Terminal Enclosure


  • Control

    Thermocouple, RTD, Thermostat, Digitally controlled


 Screw Plug Heater Construction

1. Nickel Chromium Resistance wire for high mechanical and creep strength for maximum heater life. Nickel-Chromium resistance coil is fusion welded to the metallic terminal pins.

2. High Purity magnesium oxide fill selected for maximum dielectric strength and thermal conductivity, highly compacted for maximum heat transfer.

3. Stainless steel sheath / Inconel sheath for oxidation and corrosion resistance in a wide variety of environments and are suitable for high temperatures applications


Sheath Selection Guide

The different sheath materials used in these heaters have different watt densities and operating temperatures. While choosing the sheath material following points should be looked at

  • Stainless Steel: Maximum operating temperature is 1200 °F while the maximum watt density is 120 W/in2
  • Steel: Maximum operating temperature is 750 °F while the maximum watt density is 120 W/in2
  • INCOLOY: Maximum operating temperature is 1600 °F while the maximum watt density is 120 W/in2


Sheath material

Screw plug material

Clean water, Freeze protection, hot water storage, Boiler, and water heaters, cooling towers, Solutions not corrosive to copper



Hot water, steam boilers, mildly corrosive solutions (in rinse tanks, spray washers)



Oils, Gases, Mildly corrosive liquids, stagnant or heavy oils, high temperature, low flow gas heating




Process water, soap, and detergent solutions, Soluble cutting oils, demineralized or deionized water

Stainless steel

Stainless steel

Mildly corrosive solutions

Stainless steel

Stainless steel

Severe corrosive solutions, demineralized water


Stainless steel

Light Oil, Medium Oil



Food Equipment, Food Equipment with cut out


Stainless steel



  • Clean water, hot water storage, portable water, freeze protection of liquid
  • Hot water, steam boilers, mildly corrosive solutions (in rinse tanks, spray washers), vapor degreasers
  • Severe corrosive solutions, demineralized water, food equipment