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Customized screw-plug immersion heaters

Electrical screw-plug immersion heaters are designed for heating or temperature maintaining of liquids, gas or mixture in static or circulation conditions in all industries.

The design is based on customer process conditions : fluid to heat (type and properties), in/out temperature, pressure, heat exchange conditions (stagnant or flowing), and environment conditions (ATEX or not, onshore or offshore, etc.).

The screw-plug immersion heaters are available in customized design or as a standard range.

Usual applications: Heating of circulating or static fluids like water, rinsing baths, oils, acids, thermal fluids, heavy oil, air or gas.

The heaters can be mounted in tanks, cisterns, boilers or circulation heaters.

Many industries: Petrochemicals, chemical, food, plastics, etc.

Reliability and robustness are key drivers for our engineers.

Product overview

  • Power from 100 W to 35 kW
  • Designed for pressure up to 15 bars
  • Plug in steel, brass or stainless steel


  • Large range of materials and options according to customer process and application
  • Standard range available
  • Benefit from CETAL’s 50 years of experience as designer and manufacturer!
  • The end-to-end control of the design and production chain allows us to deliver a product which suits your process perfectly

Operating conditions

  • Normal (non-ATEX)
  • Hazardous areas (ATEX/IECEx) and NEC 505
  • Extreme environments: – 60°C to + 80 °C
  • Fluid/solid: from – 270 °C (3 K) to 1000 °C
  • Onshore / Offshore environment
  • Salt atmosphere
  • Pressure: 15 bars (Brazing) (PED)
  • Vertical or horizontal mounting


  • Stagnant water, max load 8 -12 W/cm², material: copper, 321, 316L
  • Circulating water, max load 10 -16 W/cm², material: copper, 316L, inc 800, inc 825
  • Boric water, max load 8 W/cm², material: 316L
  • Boiler water, max load 8 -16W/cm², material: 316L, inc 800, inc 825
  • Chlorated water, max load 6 W/cm², material: inc 825
  • Sea water, max load 3.5 -6 W/cm², material: inc 825, inc600
  • Demineralized water / deionized / distilled / Softened,max load 4 -6 W/cm², material: 316L, inc 800, inc 825
  • Domestic hot water, max load 4 -8 W/cm², material: copper, 316L, inc 825
  • Caustic water (2%, 10%, <30%, 70%), max load 2,3-7W/cm², material: 316L, inc 825, inc 600


  • Fuel oil pre-heating,light fuel oil, C fuel oil, max load 1 -2 W/cm², material: 321, 316L
  • Heavy fuel, max load 0.5 -3.5 W/cm² accto grade, material: 316L
  • Gasoline, kerosene,max load 3.0-3.5 W/cm², material: 316L
  • Machine oil SAE 10, 30, 40 &50, max load 2.0 -3.5 W/cm², material: 316L
  • Mineral oil , max load 0.5 -3.5 W/cm² acc to temp, material: 321, 316L
  • Lube oil, max load 2.3 W/cm², material: 321, 316L

Acid & corrosive fluid

  • Acetic acid, max load 6W/cm², material: 316L, inc 825
  • Boric acid, max load 6W/cm², material: inc 825
  • Chloric, Hydrofluoric, nitric, sulphuric acid, max load 1,5W/cm², material: teflon coat
  • Boric acid, max load 6W/cm², material: inc 825
  • Alkaline bath, max load 6W/cm², material: 321 (no corrosive compound), 316L
  • Phosphate bath, max load 4W/cm², material: 316L,inc 825


  • Ethylene glycol, propylene glycol, 4 to 8 W/cm² acc. to concentration, material: 321, 316L


  • Asphalt, tar, and other heavy or highly viscous compounds, max load 0.5 -1.5W/cm², material: 316L
  • Milk, max load 0.3W/cm², material: 316L


  • Air, max load 0.1 -8W/cm² acc. to sheath temp., material: 321
  • Circulating air, max load 0.1 -8 W/cm² acc. to sheath temp., material: 309
  • Natural gas, max load 0.1 -8 W/cm² acc. to sheath temp., material: 321, 316L
  • Argon, nitrogen, W/cm² acc. to sheath temp., material: 321, 316L, inc 825, inc 600
  • Propan, butane, W/cm² acc. to sheath temp., material: 321, 316L
  • Oxygen, hydrogen, W/cm² acc. to sheath temp., material: 316L


  • Oxychloration, max load 3 W/cm², material: inc800, inc 825
  • Calcination, max load 3 W/cm², material: inc 800, inc 825
  • HC regeneration, max load 2 W/cm², material: inc 800, inc 825

Technical description

The Watt density, tube diameter and the tube sheath are chosen to optimize the reliability and robustness (corrosion, temperature) of CETAL equipments.


  • Tubular heating element (in most cases)
  • Heating rods into sleeve

Tube diameter & material

  • Tube diameter: 6.5 / 8.5 / 10 / 13.5 / 16 mm
  • Tube material:
    • Stainless steel: AISI 321 (1.4541) / AISI 316L (1.4404) / AISI 309 (1.4828)
    • Others: Incoloy 800 (1.4876) / Incoloy 825 (2.4858) / Inconel 600 (2.4816)
    • Titanium
  • Specific coating: Teflon™ (PTFE) / Halar
  • Tube type: sealed tube, seamless tube (on request)


  • 100% of the components come high quality supplier from Europe
  • 100% manufacturing in CETAL factory

  1. Connection terminals
  2. Tube
  3. Insulation : magnesia oxyde (Mg O), to secure optimized heat transfer and electrical insulation.
  4. Resistance wire: Made of Nickel Chrome 80/20, it is the active part of the heating element (Joule effect)
  5. Cold length
  6. Sealing material: Keeps out external moisture. Different types (silicon, resins, cement) are used depending on the industrialapplication, the external medium and temperature.
  7. Output insulation: Made of steatite ou corundum, it provides dielectric insulation (creepage distance, distance in the air).
  • Threaded steel or stainless steel rod: M4x0.7 (tubes ø6.5, Ø8.5 and Ø10), M5x0.8 (tubes ø13.5), M6x1 (tubes ø16).
  • Plain rod, flat terminal, tab or cable on request
  • Common diameters: 1/2″, 3/4″, 1″, 1″1/4, 1″1/2, 2″,2″1/2, M45, M77
  • Materials: Brass, stainless steel or steel on request
  • Connection: brazed or welded, depending on the application

Options: Seal and sealing nut adapted to the plug.

  • TIG Welding : CETAL has QS and QMOS certification
  • Brazing (up to 15 bars)
  • Non ATEX connecting box
    • Material: plastic, painted steel, stainless steel, aluminium
  • ATEX/IECEx connecting box
    • Explosion-proof connecting box, aluminium, Ex d IIC
    • Nickel-plated brass cable gland (stainless steel as option)
  • Fluid temperature <110°C, no offset
  • Fluid temperature >110°C, offset between the protecting box and the tank is recommended
  • Temperature sensors (thermostat, limiter, thermocouple or PT100) in the medium (process control) or on theheating element (safety control), on the flange or in the connecting box.
  • Voltage: VAC or VCC
  • Cabling according to main voltage VAC/VCC 1PH + N or 3PH
  • Power : a few Watt to several Megawatts
  • Standard documentation
    • Certificate of conformity to the order
    • Heater wiring diagram
    • Instruction manual
  • On-request documentation
    • Supplied according to directives, standard and construction code
    • Welder qualifications (QS)
    • Welding qualifications (QMOS)
    • PED documentation
    • Material certificate 3.1 acc. to NF EN 10204
  • According to CE European directives and CE market (for Europe)
  • ATEX/IECEx certificate for component or system
  • EAC CU TR, c CSA us (NEC 505)

Electrical tests

  • Power test by cold resistance measurement. Allowed tolerance: -5% and +10% of the nominal resistance value.
  • Insulationtest, direct voltage 500 V, mini cold value is > 100 Megohms
  • Dielectric test, (2U + 1000 V)  x 1,2 during 1 second
  • The stray current and the hot dielectric rigidity can be measured on a sample at operating temperature (on request).
  • 100% of the heating elements are tested before shipment (Final control)

Mechanical tests

  • Visual inspection
  • X-ray test (if required)
  • Liquid penetrant test
  • Pressure control test

Dimensional test

  • Critical dimension are tested

Other tests / operations

  • Helium test (on request)
  • Degreasing
  • Argon cleaning

Third party

  • Third party inspection (on request)

Protective enclosures

  • Large range of enclosures, different sizes, aluminum, polyamide or steel
  • Electrical degree of protection from IP40 to IP66
  • Polyamide or brass cable gland, adapted diameter, or simple grommet


Temperature control

Large range of control or safety thermostats, thermocouples and PT100 sensors, from -35 to 450°C, allowing optimum temperature control.
Temperature measurement via immersion sleeve of adapted length or directly welded on the heating element for more accuracy.



Assembly parts

Seal and sealing nut adapted to the plug, welding ring

Standard power control panels

CETAL offers a large range of cost-effective power control panels.

Vessels for circulation heaters

We provide complete circulation heaters on request.