Circulation Heaters

Circulation Heaters, also known as “in line heaters,” have uses in many applications. They can use steel, stainless steel, or titanium depending on the application. Lube oil and waste oil applications often use steel for circulation heaters. This is because it is fairly inexpensive compared to stainless steel counterpart. Water circulation heaters use stainless steel because of its anti-corrosive qualities. In both applications, a pump flows the liquid, such as water or glycerol, through a closed pipe circuit. The liquid is reheated as it flows through the circulation heater. A major consideration for this application is viscosity. Electric circulation heaters generate heat, making the medium less viscous. The less viscous the fluid, the easier it is to pump through a circuit of pipes.

Industrial circulation heaters come in a range of watt densities. Watt densities are specifically designed for the medium they will heat. The required wattage to heat the oil or water is highly correlated to the flow rate (in GPM).

  1. The fluid enters through the inlet closest to the flange heater.
  2. Heat gets applied to the fluid as it flows within a vessel chamber.
  3. The fluid exits the outlet nozzle or flange.
  4. It circulates throughout the piping circuit.

Insulation is often required for vessels to preserve the heat within the vessel. This results in efficient heat application, reducing unnecessary costs through heat loss. Electric circulation heaters can use digital thermocouple probes or RTDs. This allows them to maintain the oil or water at the preferred temperature. Many applications use liquids with low flash point. These require explosion-proof housing (NEMA 7) to avoid potential mishaps.


Wattco uses its decades of experience shipping our industrial heaters worldwide. When shipping across borders, Wattco can handle all necessary import, customs and duties responsibilities to ensure that you receive your product on time and on spec. Wattco ships using all mediums upon request including: truck, train, container ship and by air freight when mission critical rush delivery is required.

Wattco Circulation Heater Features

Other useful features found with electric circulation heaters are drain valves. They are easy to install  in any location on the vessel, allowing for easy maintenance of the heater. The water or oil can be purged through the drain valve allowing for maintenance on the heating elements. Calcium deposits and other residues can build up on heating elements. These require cleaning several times a month. Circulation heaters also come with horizontal or vertical mounting, depending on your application. Skid mounted vessels are used in oil heating industries that require mobility. WATTCO™ electric heaters are also available in different terminal boxes. These include moisture resistant or explosion proof terminal boxes for hazardous environments. WATTCO™ circulation heaters are an exceptional choice for heating process liquids. They use materials that are resistant when heating corrosive mediums.

Closed Loop Circulation Heaters

Circulation heaters are also used when heating closed loop systems. These can require high temperatures of up to 1000℉. These applications use large flange heating vessels that contain the gas and heating it efficiently. It requires low maintenance and provides excellent heat transfer.

Circulation Heaters for Oil & Gas Companies

Oil and Gas companies use circulation heaters in heating oils. Electric heaters assist them in modifying the viscosity levels of their heating oils. Crude oil enters an inlet of the vessel at a cool temperature. The circulation heater reheats the oil. The oil then exits the outlet at a temperature more convenient for flow as it travels from one end of the transport pipe to the other. Hydraulic fluid can also be heated using this electric heater for heat transfer purposes. It also provides freeze protection in cooler climates. This is crucial because winter temperatures can damage the fluid. Immersion heaters are widely used in a variety of industries. Particularly the oil and pipeline sector for several different purposes. These industrial heaters are specifically designed so that oil, water, viscous materials, gases, solvents and other different process mixtures can be heated in direct contact with each other. This allows the heat to be generated within a single enclosure or solution, and so hundred percent efficiency can be achieved. Get a quote for a circulation heater today. Also, check out our other high-quality industrial heating products in the WATTCO™portfolio.
  • Options
  • ANSI Flange

    2 INCH UP TO 42 INCH

  • ANSI Flange Rating

    150 LBS, 300 LBS or 600 LBS ANSI Non Standard Flanges also available

  • Elements

    Steel, Stainless Steel, Copper, Titanium, Incoloy, Inconel

  • Controls

    Thermostatically controlled (0-255F), (55-550F) Digitally Controlled, Thermocouple, RTD

  • Terminal Box Housing

    NEMA 1 Standard Terminal Box, NEMA 4/4X Water Proof Terminal Box NEMA 7 Explosion Proof Terminal Box

10 inch ANSI flanged heater NEMA 4 terminal box
12 inch ANSI flanged heater NEMA 4 terminal box
3 inch ANSI flanged heater NEMA 1 terminal box
3 inch ANSI flanged heater NEMA 4 terminal box
3 inch ANSI flanged heater NEMA 7 terminal box
4 inch ANSI flanged heater NEMA 1 terminal box
4 inch ANSI flanged heater NEMA 4 terminal box
4 inch ANSI flanged heater NEMA 7 terminal box
5 inch ANSI flanged heater NEMA 1 terminal box
5 inch ANSI flanged heater NEMA 4 terminal box
5 inch ANSI flanged heater NEMA 7 terminal box
6 inch ANSI flanged heater NEMA 1 terminal box
6 inch ANSI flanged heater NEMA 4 terminal box
6 inch ANSI flanged heater NEMA 7 terminal box
8 inch ANSI flanged heater NEMA 1 terminal box
8 inch ANSI flanged heater NEMA 4 terminal box
8 inch ANSI flanged heater NEMA 7 terminal box
Specifications Description
Wattage, Voltage Phase The removable flanged heater can be made of virtually any power and voltage requirements
Circuits Any specified by user
Flange and Vessel 3 inch, 4 inch, 5 inch, 6 inch, 8 inch, 10 inch 12 inch, 14 inch up to 43 inch flanges of any material type required
Flange and Vessel material Carbon steel, carbon steel galvanized, 304 stainless steel, 316 stainless steel, incoloy, inconel, titanium
Flange Rating Class 150, class 300 or any specified
Wearing Watt density 6.5 W/In2  15 W/In2  23 W/In2  45 W/In2 65W/In2 or any other
Sheath material Steel, Copper, 304 Stainless Steel, 316 Stainless steel, Incoloy
Terminal seals silicone resin, silcone fluid, RTV, epoxy, hermetic or any other
Terminal enclosure NEMA 1 General purpose, NEMA 4 moisture resistant, NEMA 7 Explosion proof
Terminal Enclosure Standoffs 4 inch, 6 inch or any other
Flange Gasket Standard, Spiral wound or any other
ASME Designed if needed
Thermal Insulation Standard, High Temperature or weatherproof jacket available
Mounting position Horizontal or vertical
Lifting lugs If required



Circulation Heater Applications SHEATH MATERIAL FLANGE MATERIAL
Clean water, Freeze protection, hot water storage, Boiler and water heaters, cooling towers, Solutions not corrosive to copper Copper Steel
Hot water, steam boilers, mildly corrosive solutions (in rince tanks, spray washers) Incoloy Steel
Oils, inline gas heating, Mildly corrosive liquids, stagnant or heavy oils, high temperature, low flow gas heating Steel Steel
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 Incoloy Stainless Steel
Light Oil, Medium Oil Steel Steel
Food Equipment Incoloy Stainless Steel


Key Features Benefits
 Standard sizes: 1.25” NPT Screw Plug size to 14” diameter

  • Steel or stainless vessels fitted with 150 lb./300 lbs/ 600lbs/ 2000 lbs. psi flanges
  • Thermal insulated vessels
  • Custom unit sizes
  • Custom-designed to meet your specifications
  • Special sizes, wattages, and materials are available upon request 
  • Units are available with larger vessels and heavier flanges
  • Can be supplied with stainless steel parts and special design terminal boxes for heat    protection and use in high temperature conditions.
  • Insulated upon request


  • Easy to install
  • Compact
  • Clean
  • Durable
  • Highly energy efficient
  • Provide fast response and even heat distribution 
  • Provide greater wattage in a smaller heater bundle
  • Provide maximum dielectric strength
  • Reduce heat loss from the vessel
  • Protect and prevent from thermal insulation
  • Easy mounting support
  •  Suitable to general purpose terminal enclosures, NEMA 7, NEMA 4X NEMA 7, and unsafe or explosion proof locations
  • Compatible with standard industry piping and safety standards
  • Designed and built for safety
  • Works in conjunction with Control Panels



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