After the heating wire placed inside the cartridge heater has been heated, it forms a very thin oxide film which crystallized by high temperature. Once cooled, the heating wire is contracted. The oxide sheet breaks and exposes a fresh layer wire but smaller in diameter. Cyclically repetition of this process is the main cause of heating wire breakings. Therefore it is recommended to use a fixed temperature with suitable power and not energize and de-energize. This process can also cause a different Ohm value registration during his life.
Maxiwatt´ s heaters are the most compacted. Even so we have available special manufacturing systems to support excessive vibrations or repeated blows.
That information must be on the purchase order, otherwise we will produce them with a standard ending. Vibrations and impacts will gradually damage the internal compression until the wire comes in contact with the atmosphere and oxide.Cartridge heaters are basically formed by ceramic powder and Magnesium Oxide. This last one is very hydroscopic and absorbs the moisture. Together with the process of expansion and retraction, when a cartridge heaters is energized the leads absorb all type of liquids and gases around, such as moisture, water, oil, polish, melted plastics, brine, organic debris, detergents, etc.
Elements that in normal conditions are harmless, when the cartridge is warm will be absorbed by the heater and produce an internal pollution. At the same time a short-circuit will reduce the heating wire and the heater will lose the electrical insulation.An overheating at the leads cause damages at the heater. The element will lose the insulation protection causing short-circuit. Excessive vibration and movement causes breakage. Maxiwatt offers different type of leads for each use and specific protections over the leads.
Thermocouples and sensor should be placed in the hottest part of the mold or piece. If they are placed in other positions the heater must do an extra work due to the effort it must do to get the desired temperature. So that the heater will work over his normal conditions and that will reduce the elements life.
| Breakage by | Over temperature | Repetitive cycles | Pollution | Leads |
|---|---|---|---|---|
| Rated over temperature | Total cooling and maximum wire heating | Absorption of contaminating elements inside the cartridge heater like moisture, water, oil, plastic, brine, etc. | broken or unprotected. | |
| Effect | Heating wire melts or loses its insulation | Dilation or contraction of the wire will finally reduce it or break itself due to the oxidation. | Short circuit, due to an internal contamination that causes grounding of the element. | No electricity input in the circuit or grounding due to a non insulation. |
| Reasons | Poor heating dissipation. | Working without any external regulator at maximum capacity and total disconnection until the element is cold, during short and repetitive cycles. | Moisture condenses forming a bridge between the heating wire, sheet and leads. Producing short-circuit. Materials that in normal do not conduct electricity can do it after support high temperatures and be charred. | Vibrations, movement, impacts and high temperatures at leads side. Also leads inside the hole. |
| Appearance | Blue tones and also dark brown with small oxide layer in parts where the cartridge heater Is not in contact with the hole. | heating element fusion. | Standard colors on the heater. Internally different colorations and steel sheet crater-shaped.. | Rubbings, peels, cuts, material breakup. |
You can think that previous elements had a longer life. We can say that there are lot of different reasons that can cause a premature breaking. First of all you must analyze the previous element and check the internal construction (cold zones, wire thickness, isolation, granulometry, compression). These details can help us to check if two cartridge heaters with the same external length have the same internal heating zone. They can have a longer active zone and this part can be placed outside the hole, that causes an overheating and short-circuit. Both elements are perfectly produced, with details provided, and have the same appearance but internally they are different.
By the other hand, you should also control that the hole where the heater is placed must have a perfect tolerance type H7. Holes can have reduction in diameter due to the continuous friction when elements are installed. That occurs also due to the dilation or contraction of the elements causing a wrong diameter size.
When a new cartridge heater is placed in the hole and it has a wrong tolerance, we mean diameter -0.02mm to -0.06mm, the heater can´t dissipate the heating correctly and that will reduce heaters life.
