Screw Plug Heater

Screw Plug Immersion Heaters consist of hairpin tubular elements welded or brazed into a screw plug and provided with terminal enclosures for electrical connections. They can be screwed through a threaded opening into a tank wall or vessel. Welding or brazing depends upon the element sheath and plug material compatibility. Depending upon the customer requirement, thermo wells, thermostats or control panels can be used with these heaters to meet the objective of precise temperature control.

Screw Plug Heaters are smaller version of Immersion Heaters in which heater flange in replaced with a threaded plug. Used as a direct heating element, they are ideal for heating gases and liquids in tanks or vessels, process water heating, oils and heat transfer process, heating up flammable liquids or gases which require explosion proof housing. Screw plug heaters are widely used for various purposes in many industries including the food and beverage industry. In addition to the general use of boiling water and freeze protection, it is extremely useful for the purpose of steam generation. They are highly energy efficient and easy to regulate. The installation is a snap and the maintenance is very easy as well.

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.

Note- For custom design requirements please contact sales@marathonheat.com


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Sheath Material Copper, Steel, 304 Stainless steel, INCOLOY
Watt Density Up to 120 W/inch²
Screw Plug Material Stainless steel, Brass, Steel, Titanium
Screw Plug NPT fittings 1 to 4 inches
Diameter 0.260”, 0.315”, 0.375”, 0.430” and 0.475”
Voltage 120 to 480 V AC Single phase or three phase
Terminal Enclosure IP 23 Standard Terminal Box,

IP 66 Water Proof Terminal Box

Control Thermocouple, RTD, Thermostat, Digitally controlled


Clean water, hot water storage, portable water, freeze protection of liquid Copper Steel
Hot water, steam boilers, mildly corrosive solutions (in rinse tanks, spray washers), vapor degreasers Incoloy Steel
Oils (light or medium), Gases, hydraulic oil, stagnant or heavy oils, lubricating oil, crude asphalt Steel Steel
Process water, soap and detergent solutions, Boiler and water heaters, demonized water, chemical baths, mildly corrosive solutions. Stainless Steel Stainless Steel
Severe corrosive solutions, demineralized water, food equipment Incoloy Stainless Steel
  • Efficient Heating and operation.
  • Less probability of breakdown.
  • No expensive repair cost.
  • Environmental performance.
  • Improves personal and industry safety.
  • Easy to install.
  • Easy to regulate & maintain.