Circulation Heaters

Circulation Heaters also known as “in line heaters” use steel, stainless steel, and titanium in many applications. Lube oil and waste oil applications often use steel for circulation heaters as it is fairly inexpensive compared to stainless steel counterpart. Water circulation heaters are made with stainless steel because of its anti-corrosive qualities. Both applications involve using a pump that flows the liquid through a closed pipe circuit (IE. water or glycol solution) that is reheated. A major consideration for this application is viscosity. Heat that is generated by the electric heater allows the liquid to be viscous enough to pass through the circuit of pipes. Circulation heaters come in a range of watt densities that are specifically designed for the medium that is heated. The required wattage to heat the oil or water is highly correlated to the flow rate (in GPM). The oil or water enters through an inlet (the inlet closest to the flange heater) and gets heat applied to it as it flows within a vessel chamber and exits the outlet nozzle (or flange) where it circulates throughout the piping circuit. Insulation is often required for vessels in order to preserve the heat to be applied within the vessel. Efficient heat application can often reduce unnecessary costs through heat loss. Digital thermocouple probes or RTDs, can be used with the electric heaters to maintain the oil or water at the preferred temperature. Many applications use liquids with low flash point and, require explosion proof housing (NEMA 7) to avoid potential mishaps.

Digital Control Panel w/ Inline Circulation Heater Other useful features found with electric circulation heaters are drain valves. They can be installed in any location on the vessel and allow for easy maintenance of the heater. The water or oil can be purged through the drain valve allowing for maintenance on the elements. Calcium deposits and other residue can be found on elements and should be cleaned several times a month. Circulation heaters also come with the choice of horizontal or vertical mounting depending on your application. Skid mounted vessels are used in oil heating industries that require mobility.

WATTCO™ heaters are also available in moisture resistant terminal boxes or explosion proof terminal boxes for hazardous environments. WATTCO™ Circulation heaters are an exceptional choice for heating process liquids, non-corrosive to the materials of construction. Circulation gas heaters are also used when heating closed loop systems that require high temperatures of up to 1000 deg F. These applications use large flange heating vessels that contain the gas and heat it up in containment most efficiently requiring low maintenance and excellent heat transfer.

Oil and Gas companies have specifically used circulation heaters to assist them in the process of modifying viscosity levels of their heating oils. Crude oil enters an inlet of the vessel at a cool temperature and 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, and to resist cooler climates as winter temperatures need to be avoided. 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.

  • 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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