An Internally Wired Miniature Heating Cartridge is a tubular electric heating element that seals a heating conductor (resistance wire) inside a miniature metal tube, with the lead wires or rods directly connected to the heating coil internally. Its core feature is "internal wiring," meaning the electrical connection is completed inside the tube, resulting in a compact structure, excellent sealing, and a long service life.

 

1. Materials

· Metal Sheath (Outer Casing):

· Stainless Steel 304: The most common material, offering good corrosion resistance and heat resistance. Suitable for most applications like heating water, oil, and air.

· Stainless Steel 316/316L: Offers superior corrosion resistance, particularly against chlorides and acids/alkalis. Used in more demanding environments like marine or chemical industries.

· Titanium: Primarily used for heating plating solutions (e.g., chromic acid, acid copper) and chemical liquids. Provides excellent resistance to chloride ion corrosion.

· Teflon (PTFE): Features exceptional resistance to strong acids and alkalis and a non-stick surface. Often used for heating highly corrosive liquids.

· Inconel: Exhibits extreme high-temperature and oxidation resistance. Commonly used in high-temperature furnaces or special industrial environments.

· Internal Heating Coil:

· Typically made of Nickel-Chromium (NiCr) or Iron-Chromium-Aluminum (FeCrAl) alloy wire, which have high resistivity and stable high-temperature oxidation resistance.

· Insulation Filling:

· High-Purity Magnesium Oxide (MgO) Powder: The standard filler. It possesses excellent electrical insulation, thermal conductivity, and heat resistance, efficiently transferring heat from the coil to the metal sheath while ensuring electrical insulation.

· Sealing Material:

· Special high-temperature, moisture-resistant silicone glue, epoxy resin, or ceramic cement is used to seal the tube ends, preventing moisture ingress and ensuring long-term stable insulation.

· Lead Wires / Terminals:

· Usually made of stainless steel, nickel-plated copper wire, or silicone high-temperature wire, directly connected to the internal heating coil and extended from the tube ends.

 

2. Dimensions

The dimensions of miniature heating cartridges are highly flexible and can be customized according to customer requirements.

· Tube Diameter: Typically ranges from φ2mm to φ10mm. Common sizes include φ3mm, φ4mm, φ6mm, and φ8mm.

· Length: Virtually unlimited, from as short as 20mm to several meters long. Common lengths are between 50mm and 500mm.

· Shape: Besides straight rods, they can be bent into U-shape, L-shape, W-shape, annular (loop), or various custom shapes to fit different installation spaces and heating requirements.

 

3. Voltage

· The operating voltage range is very wide. Common standards include 12V, 24V, 36V, 48V, 110V, 220V, and 380V.

· Low Voltage (e.g., 12V/24V/36V): Typically used in applications with high safety requirements, automotive devices, or when integrated with control systems (e.g., PLC, temperature controllers).

· Standard Voltage (e.g., 110V/220V): Used for conventional industrial and commercial equipment.

· Voltage selection must match the power and resistance values (according to the formula P = V² / R).

 

4. Power

· The power range is extremely broad, from a few watts to several thousand watts.

· Surface Load (Power Density, unit: W/cm²) is a critical parameter, determined by voltage, resistance, diameter, and length.

· Low Surface Load: Typically below 5 W/cm², used for heating media like oil to prevent carbonization from excessive surface temperature.

· Medium-High Surface Load: Can reach 10 ~ 30 W/cm² or higher, used for heating air, water, etc.

· Important Note: Power setting must consider the heated medium and operating conditions. When operating in air (dry firing), the surface load must be reduced; otherwise, the cartridge may overheat and burn out due to insufficient heat dissipation.

 

5. Primary Applications

Due to their miniaturization, high efficiency, and flexibility, internally wired miniature heating cartridges are widely used in:

· Home Appliances: Coffee makers, garment steamers, water dispensers, instant hot water taps, dishwashers, warm air blowers.

· Industrial Equipment:

· Plastics Machinery: Heating barrels for injection molding machines and extruders.

· Packaging Machinery: Heating for heat seal bars and packaging machines.

· Analytical Instruments: Sample heating in gas chromatographs, water quality analyzers.

· Medical Equipment: Sterilization equipment, heated breathing circuits for ventilators, infusion warmers.

· Semiconductor Manufacturing: Wafer baking, photoresist processing.

· Automotive Industry: Diesel fuel tank heating, AdBlue (DEF) tank heating, seat heaters, mirror defrosting.

· Fluid Heating: Precise heating for various liquids (water, oil, acids, alkalis) and gases (air, nitrogen).

 

6. Product Characteristics

· Compact Structure, Small Size: The "miniature" design allows installation in space-constrained equipment.

· High Thermal Efficiency, Rapid Heating: Small diameter results in low thermal mass, enabling quick reach of operating temperature.

· High Mechanical Strength, Pressure and Shock Resistant: The metal sheath and dense MgO filling allow it to withstand certain levels of pressure and mechanical shock.

· Safe, Reliable, Long Lifespan: The "internal wiring" structure and strict sealing effectively prevent moisture and leakage, ensuring high electrical safety and a long operational life (thousands of hours under proper use).

· Excellent Sealing Performance: Can operate in specific pressure environments or be used for heating liquid media.

· High Power Density: Capable of achieving high heating power in a very small volume.

· Highly Customizable: Dimensions, shape, voltage, power, and lead wire configuration can all be customized based on customer needs, offering great adaptability.