Explore the differences between tubular heaters and cartridge heaters

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Heating Showdown Tubular Heaters vs. Cartridge
Heaters Unveiling the Key Differences

• NexThermal Mfg (I) Pvt Ltd

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Tubular Heaters vs. Cartridge Heaters

• Heating elements are essential components in many
  industrial processes and commercial appliances.
• Two of the most common electric heating elements
  are tubular and cartridge heaters.
• While both serve the purpose of converting
  electrical energy into heat, there are some key
  differences between the two that impact their
  optimal applications and performance.

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Overview of tubular and cartridge heater designs

• Tubular heaters consist of a metal tube (usually
  stainless steel or alloy steel) that contains a
  coiled heating wire. The tube protects the wire
  and provides efficient heat transfer.
• Cartridge heaters have a cylindrical shape but
  lack an outer metal sleeve. Instead, the heating
  element wire is insulated with magnesium oxide
  and enclosed in a stainless-steel sheath.
• This allows insertion into drilled holes.

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Some key physical differences between the two

• Tubular heaters consist of a metal tube
  surrounding a heating coil.
• Cartridge heaters have an insulated heating wire
  pressed into a metal sheath.
• Tubular heaters can be much longer than cartridge
  heaters. Tubes over 36 inches are common.
• Cartridge heaters are limited to shorter lengths,
  typically under 16 inches.
• Tubular heater diameters range from 0.25 inch to
  2 inches. Cartridge diameters span 0.25 inch to 1
  inch.
• Tubular heaters can handle higher wattage
  densities than cartridge heaters.
• Now that weve compared the basic designs lets
  look at how these physical factors influence the
  performance and applications of tubular and
  cartridge heaters.

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1. Temperature capabilities

Key performance differences

• The maximum temperature a heater can reach
  depends on the materials used in its
  construction.
• Tubular heaters made from steel alloy tubes can
  withstand temperatures up to 1400F. Stainless
  steel tubes allow temperatures up to 1600F.
• Cartridge heaters typically max out at lower
  temperatures, around 750F for stainless steel
  sheathed heaters. However, Incoloy sheathed
  cartridge heaters can reach 1200F.
• The ability to handle higher temperatures makes
  tubular heaters better suited for processes like
  heat-treating metals, preheating combustion air,
  and maintaining molten polymers.
• Cartridge heaters are often selected when
  temperatures below 1000F are needed, such as
  warming adhesives or heating diesel fuel.

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2. Watt density and wattage output

• Watt density refers to the number of watts
  dissipated per square inch of heater surface
  area. A higher watt density means more watts can
  be packed into a smaller space.
• The tubular design allows tubular heaters to
  achieve watt densities over 100 w/in2. Cartridge
  heaters typically max out around 60 w/in2.
• Higher watt densities enable tubular heaters to
  deliver more power overall. Tubular heaters are
  available for over 70 kW, while most cartridge
  heaters top below 2 kW.
• When high heat output is required in a compact
  area, tubular heaters have the advantage.
  Cartridge heaters are often favored for
  lower-wattage applications

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3. Duty cycle rating

• A heaters duty cycle describes how long it can
  operate at full-rated power without overheating.
  This is expressed as a percentage or minutes per
  hour.
• Tubular heaters often have a 100 continuous duty
  cycle rating, meaning they can run steadily at
  full power.
• Cartridge heaters are only rated for intermittent
  operation, around 25 duty cycle. This equates to
  15 minutes per hour at full-rated wattage.
• The tube metal in tubular heaters provides a more
  effective dissipation of heat generated by the
  internal coil. The compact cartridge design lacks
  this additional heat-sinking ability.
• For applications requiring constant heating,
  tubular heaters are the better choice. Cartridge
  heaters work well for short-burst heating needs.

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4. Robustness and durability

• The metal tube encasing the heating element makes
  tubular heaters durable and resistant to damage.
  They can withstand harsh industrial environments
  and vibration without failure.
• Cartridge heaters lack an outer metal sleeve,
  making the heating wire vulnerable. Care must be
  taken to avoid crushing the cartridge or exposing
  the internal coil.
• Tubular heaters also handle high-pressure
  washdown and moisture better. Their screen
  barrier helps prevent water ingress. Cartridge
  heaters rely on potting compounds and seals to
  protect the element.
• Tubular heaters are often preferred for critical
  applications where ruggedness and reliability are
  priorities. Cartridge heaters may make sense for
  gentler low-pressure uses.

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5. Flexibility and shape options

• Tubular heaters are produced in straight or bent
  tubes, allowing some flexibility in shape. But
  they are still essentially limited to a
  cylindrical form.
• Cartridge heaters can be manufactured in
  straight, L-shaped, and helical coiled designs.
  This allows cartridges to fit unique spaces and
  wrap around components.
• When flat or contoured heating surfaces are
  needed, cartridge heaters provide more
  variability. Tubular heaters offer simplicity and
  consistency in basic tube shapes.

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6. Cost considerations

• Tubular heaters generally have a higher upfront
  cost than comparable cartridge heaters. The metal
  tube adds material and manufacturing costs versus
  cartridge heaters.
• However, the higher duty cycles and lifetimes
  achieved with tubular heaters can lead to lower
  operating costs in the long run. The increased
  robustness also means fewer unexpected failures
  and less downtime.
• Cartridge heaters provide a lower initial price
  point but may need replacement more frequently.
  Determining the total cost of ownership helps
  identify the better value.

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Typical applications and uses
1. Tubular heaters applications
2. Cartridge heater applications

• Heating liquid baths and tanks
• Maintaining molten metals like zinc, tin, and
  bitumen
• Preheating combustion air for ovens and furnaces
• baking and drying ovens
• Plastic injection molding nozzles and barrels
• Gas line and pipe heating
• Industrial process heating

• Diesel fuel heating
• Adhesive melting pots
• Hot stamping tools
• Medical equipment sterilization
• Food service equipment warming
• Shrink wrap machines
• Packaging equipment, seaming tools

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Installation and maintenance

• Proper installation and maintenance help ensure
  optimal performance and lifetime for tubular and
  cartridge heaters. Here are some best practices
• For tubular heaters
• Ensure heater tubes are properly inserted into
  bored holes. Use thermal grease to aid
  conduction.
• Avoid bending tubes tighter than the minimum
  recommended bend radii.
• Use insulated power leads rated for max
  temperature and wattage.
• Allow space for air circulation around the heater
  body.
• Check for leaks and inspect for damage during
  routine maintenance.

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• For cartridge heaters
• Never insert cartridges beyond the recommended
  insertion depth.
• Apply thermal paste inside holes to maximize
  contact.
• Secure cartridge flanges with plates or collars
  when possible.
• Using short power leads to minimizing the heating
  of wires.
• Ensure wet or high moisture conditions are
  avoided.
• Check cartridge seals and terminals during
  routine maintenance.
• Adhering to manufacturers recommendations can
  maximize heater lifespan and safety.

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Choosing between tubular and cartridge heaters

• When selecting a heating element for an
  application, consider these key factors
• Required power output and temperature rating
• Available space and shape needs
• Duty cycle and longevity demands
• Environmental and safety concerns
• Tubular heaters tend to be better choices for
  applications like
• High temperature (above 750F) heating
• Continuous, intensive industrial processes
• Large tanks and baths needing high watt densities
• Harsh, high-moisture environments

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• Cartridge heaters offer advantages for
• Compact spaces requiring short heating elements
• Lower temperature (below 750F) intermittent uses
• Custom shapes and sizes
• Cost-sensitive, replaceable applications
• Of course, many factors beyond those compared
  here may apply to specific heating situations.
  Working with a qualified heating element supplier
  is the best way to ensure you get the right
  tubular or cartridge heater for your unique
  needs.

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Conclusion

• Tubular and cartridge heaters provide localized
  heat for various industrial and commercial
  applications. Understanding the key differences
  in their construction and performance allows
  selecting the right heater for optimal results
  and cost-effectiveness.
• Tubular heaters offer high temperatures, watt
  densities, and durability in basic cylindrical
  shapes. Cartridge heaters provide more
  flexibility and lower costs for intermittent
  lower-temperature uses. With careful selection,
  installation, and maintenance, tubular and
  cartridge heaters can provide long-lasting,
  efficient heating solutions.

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