Once the heating wire inside the cartridge is heated, a thin oxide layer forms and crystallises due to high temperature. When cooled, the wire contracts, breaking the oxide layer and exposing a thinner section of wire. This cyclical process is the main cause of heating wire failure. A fixed temperature and suitable power are recommended to prevent this, as well as avoiding constant switching on and off. This process may also result in a different Ohm value during the heater's life.
Maxiwatt heaters are the most compact. Nevertheless, we have special manufacturing systems available to withstand excessive vibrations or repeated impacts.
This information must be included in the purchase order; otherwise, we will produce them with standard termination. Vibrations and impacts gradually damage internal compression until the wire is exposed to air and oxidises.Cartridge heaters are primarily made of ceramic powder and magnesium oxide. The latter is highly hygroscopic and absorbs moisture. Combined with expansion and contraction, energising the cartridge allows surrounding liquids and gases—such as water, oil, polish, molten plastics, brine, organic residues, detergents, etc.—to be absorbed by the wires.
Elements that are harmless under normal conditions are absorbed by the heater when hot, causing internal contamination. At the same time, a short circuit reduces the heating wire and causes loss of electrical insulation.Cable overheating damages the heater. The element loses its insulating protection, causing a short circuit. Excessive movement and vibration cause breakage. Maxiwatt offers different cable types for each use and specific protections for cables.
Thermocouples and sensors should be placed in the hottest part of the mould or component. If placed elsewhere, the heater must work harder to reach the desired temperature, which leads to overheating and reduces the element’s lifespan.
| Breakages due to | Excessive temperature | Repetitive cycles | Contamination | Leads |
|---|---|---|---|---|
| Nominal overheating | Total cooling and maximum cable heating | Absorption of contaminants inside the cartridge heater such as moisture, water, oil, plastic, brine, etc. | broken or unprotected. | |
| Effect | The heating wire melts or loses its insulation | The expansion or contraction of the wire will eventually reduce or break it due to oxidation. | Short circuit caused by internal contamination that grounds the element. | No electrical input into the circuit and no grounding due to lack of insulation. |
| Reasons | Poor heat dissipation. | Operation without any external controller at full capacity and complete disconnection until the element cools, during short, repetitive cycles. | Moisture condenses forming a bridge between the heating wire, the foil, and the cables, causing a short circuit. Materials that normally don’t conduct electricity may do so after exposure to high temperatures and becoming carbonised. | Vibrations, movement, impacts and high temperatures on the cable side. Also inside the bore. |
| Appearance | Blue and dark brown tones with a thin oxide layer on areas where the cartridge heater is not in contact with the bore. | fusion of the heating element. | Standard colours on the heater. Internal discolouration and crater-shaped steel sheet. | Scratches, peeling, cuts, material breakage. |
One might think previous elements had longer lifespans. There are many reasons for premature failure. First, the previous element should be analysed and internal construction checked (cold zones, wire thickness, insulation, granule size, compression). These details help determine if two cartridges of the same external length have the same internal heating zone. The active zone could be longer and lie outside the bore, causing overheating and a short circuit. Both elements may look identical but differ internally.
On the other hand, ensure the hole where the heater is placed has a perfect H7 tolerance. Holes can reduce in diameter due to repeated friction during installation, or due to expansion/contraction of the elements, resulting in incorrect diameter size.
When a new cartridge heater is placed in the bore with incorrect tolerance (diameter -0.02 mm to -0.06 mm), the heater cannot dissipate heat correctly, reducing its lifespan.
