Heavy-oil preheaters


Heavy-oil preheaters are a variant of the electrical flow-type heaters.

They are designed for efficiently heating heavy oil to adjust the proper viscosity for the burner. The design is based on the general conditions such as the type and properties of the respective fluid, pressure and temperature as well as the desired operating points in the process.

Electrical heavy-oil heaters directly heat fuel by converting electrical energy in the heating rods to thermal energy. The thermal energy is then transferred from the heating rods to the fluid. Here, it is important that the design be matched to the general conditions, for each fluid has its specific properties.


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Fluid connections

Electrical heavy-oil preheaters heat - of course - heavy oil to adjust it to the needed viscosity which is required by the downstream separators or burners. There are different qualities of the heavy oil:

I. Heavy oil

  • Bunker B
  • Bunker C

For reasons of procurement or prices other materials can be burnt partially such as, for example:

II. Other fuels

  • Animal fat
  • Palm oil
  • Waste oil

If these fuels must also be covered, the heavy-oil preheater requires a special design. We are prepared to advise you.

The fluid to be heated and the application temperature mainly define the materials which can be used for the unheated and/or heated surfaces. Otherwise, corrosion may quickly result in a failure of the flow-type heater, especially if not only heavy oil but also other fuels are heated.

Materials of the wetted and unheated components of the heavy-oil preheaters

  • Carbon steel
  • Corrosion-resistant stainless steel

Materials of the heating surface:

  • Carbon steel
  • Corrosion-resistant stainless steel

The design of the individual heating elements is a function of the application. Normally, we use mechanically sturdy design for heavy-oil preheaters. Also, a distinction is made between compacted heating elements and heating elements where the internal heating insert can be replaced without the necessity of draining the fluid.

I. Heating elements

  • Tubular heaters, diameter 16 mm
  • Cartridge-type heaters, diameter 16, 18 or 25 mm
  • Exchangeable heating elements, including a protective tube, diameter 25, 42 or 65 mm

Electrical flow-type heaters can both be equipped with a built-in control system (for low power) or an external switchgear cabinet or for load switching by customer-provided switchgear and control gear. The electrical heating power can be divided into one or several heating stages. This division can individually be adjusted to match the control equipment.

I. Controllers

  • Electronic ON-OFF control or PID control. (-> ON-OFF control switches off the heater if the temperature is exceeded, and switches it on again when the temperature falls below its lowest value. Thus, the temperature will always oscillate around the setpoint. The algorithm of the PID controller will optimally compensate the control fluctuations.)
  • Load switching by contactors or wear-free semiconductors (thyristors). (-> contactors are wearing parts and must be replaced after approx. 100,000 make/break operations; thyristors switch quickly and without any wear but generate more heat losses than contactors.)
  • Electromechanical control.
    Thermostats installed in the electrical flow-type heater are price-efficient controllers whose accuracy is sufficient for many applications.

II. Sensors

  • Thermal protectors and limiters as capillary thermostats (as a safety design as well).
  • Temperature sensors for the fluid and heating rod temperature.
  • Overheating protection for the heater or electrical terminal compartment.

Heavy oil cannot be pumped in a cold condition To ensure a proper start of the plant, the following possibilities can be used:

  • Start-up arrangement Only useful, if an infinitely variable selection (thyristor controller) is available.
  • Rinsing with fuel oil (EL) Must be provided on site. In this case, the heater is switched off.
  • Thawing heater in the heater This additional heater keeps the heater to temperature and must be switched together with the pipe tracing of the feeding or discharging lines.

The electrical flow-type heaters can be delivered without insulation (for a customer-provided insulation) or with insulation. The insulation can be designed as follows:

I. Insulation material

  • Mineral wool with a galvanized or aluminium-coated metal jacket.
  • Diffusion-tight or gas-tight insulation
  • Insulation for indoor or outdoor installation

We are prepared to agree with you on the type and position of the fluid connections. The following connections are available:

I. Fluid connections

  • Standard flanges (DIN, ASME, SAE etc.)
  • Female or male thread connections
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