For example, these fluids are heated in electrical process heaters:
I. Water
- Drinking water, max. surface load 4 – 6 W/cm² pending on the water
- Circulating and/or heating water, max. surface load approx. 10 W/cm²
- Softened water; observe the maximally admissible chloride content, max. surface load approx. 10 W/cm²
- Ultra-pure water; here, a virtually low-pocket or pocket-free design with defined surface quality is useful.
- Fully desalted water; here, non-ferrous heavy metals should not be used, maximum surface load approx. 10 W/cm²
II. Oil
- Heavy oil, not pumpable in a cold condition, maximum surface load between 1 and 2 W/cm² depending on the quality
- Hydraulics oil, maximum surface load approx. 0.6 – 1.2 W/cm²
- Lubricating oil, steam turbine oil, max. surface load approx. 1 W/cm²
- Insulating oil, maximum surface load approx. 0.3 – 0.6 W/cm²
- Heat transfer oil, film temperature calculation acc. to DIN 4754 required, maximum surface load approx. 10 W/cm² depending on the flow velocity and oil
- Fuel oil, diesel, heating to max. 40 °C, max. surface load approx. 4 W/cm²
III. Gases
- Air
- Natural gas
- Flue gas
- Nitrogen
- Steam for overheating
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, for example.
Materials of the wetted and unheated components
- Carbon steel
- Corrosion-resistant stainless steel
- Heat-resistant stainless steel
- Titanium, Hastelloy, special materials
- Brass
Materials of the heating surface:
- Carbon steel
- Corrosion-resistant stainless steel
- Heat-resistant stainless steel
- Titanium, Hastelloy, special materials
The design of the individual heating elements is a function of the application. There are faster or slower heating elements, mechanically robust or more filigree designs. 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 8.5 or 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 process 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.
The switching devices as required for the operation of the process heater can optimally be matched to the process and the heating element they can be ordered from heatsystems
Also, the communication of the switching devices with the higher-level control system will of course be matched to the requirements exactly.
I. Switching devices
- Flow-monitoring device
- Low-water level protection
- Min. and max. pressure limiter
- Thermometer for indicating the temperature on site
The electrical process 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
- Clamp flanges
- Sterile flanges
- Dairy-type pipe connections
