How Do Cartridge Heaters Get Made? The Distinction Between Intermittent and Continuous Duty Cartridge Heaters

How Do Cartridge Heaters Get Made? The Distinction Between Intermittent and Continuous Duty Cartridge Heaters

When transferred to an intermittent cycling machine, a cartridge heater that has been dependable for months on a continuous manufacturing line may rapidly fail. The duty-cycle design created during manufacture is the cause of this discrepancy. Examining the manufacturing process of cartridge heaters aids in differentiating between continuous-duty and intermittent-duty designs and choosing a cartridge heater that complements the equipment's operating rhythm.

Continuous duty refers to the cartridge heater's ability to run continuously for extended periods of time. For consistent heat dissipation, the coil winding and magnesium oxide compaction are optimised. Experience has shown that in order to prevent heat buildup inside the cartridge heater, continuous-use cartridge heaters employ a slightly lower watt density. Internal materials are chosen to withstand creep caused by prolonged high temperatures.

Equipment with intermittent duty undergoes frequent cycles of heating and cooling. The cartridge heater experiences alternating expansion and contraction stress due to rapid temperature fluctuations. In actuality, stronger attachment is needed for the coil assembly for intermittent service. To withstand cyclic mechanical load for the cartridge heater, manufacturers optimise coil spacing and improve magnesium oxide compaction.

The duty cycle requirements are also followed when choosing the sheath material. Standard 304 stainless steel sheaths can be used for continuous low-medium temperature applications. For the cartridge heater, frequent fast thermal shock requires an Incoloy sheath because it maintains mechanical strength better under abrupt temperature changes.

Additionally, end sealing needs to adjust to heat cycling. Inorganic ceramic sealant is better than organic sealant for sporadic use. After several heat cycles, the organic sealant will fracture, enabling dust and moisture to enter the cartridge heater and harm the insulation.

During the design process, working cycle frequency and on-load time should be communicated. During production, sealing material, powder compaction, and coil layout can all be altered. For batch thermal processing equipment, heat presses, and cyclic moulding, a duty-cycle matched cartridge heater ensures steady performance.