Category: high density cartridge heaters

The making of cartridge heaters

Termination Types

No matter what the type, or use of the cartridge heaters may be, the major components are almost similar, but they are altered or changed to meet size and heat requirements. A crucial factor that the designers of cartridge heaters are the most considerate about is, watt density. Watt density is the rate of heat that gets transferred from the heater’s surface.

Watt density is a deciding factor that decides how long the cartridge heater can last. With an increase in the value of the watt density, there is a proportional increase in the temperature within the cartridge heater. This significant increase in temperature can be responsible for pushing the components of the cartridge heater to its breaking point. Operating in such circumstances can reduce the life of a cartridge heater considerably.

The making of cartridge heaters

The basic components of a cartridge heater include the cartridge heater’s sheath, its ceramic core, the lead wires, resistance wires, and the insulation. These core components are at times arranged in different ways by manufacturers in order to enhance the heating capabilities and quality of their products.

In comparison, cartridge heaters that have split sheath lack a core but do have the running wire that’s packed tight in an insulating material. Split sheath cartridge heaters are new arrivals by design and they are improvisations to existent design with intention of overcoming their flaws.

Core

Despite ceramic being the more commonly used type of core, use of magnesium is also the norm. For cartridge heaters with a core, the core often has a resistance wire wound around it. The resistance wire is made of nickel chromium.

Heating Coil

The heating coil acts as the resistance wire for the electrical load. There are many different options available for resistance wire. The most popular and common variety is nickel chromium (NiCr), or nichrome, a type of wire that is often used in heating elements like space heaters and toasters. When speaking about the other electrical heating elements, the number of turns per inch wound around the core decides the watt density. It is heated by the current flowing through the wire, which in turn heats the sheath of the cartridge heater.

Insulation

The sheath is filled with insulation to avoid the resistance wire from touching the sheath, which is often magnesium oxide (MgO). If the resistance wire is permitted to touch the sheath, it would short circuit,  ground, and melt the sheath resulting in heater failure. When the sheath is being filled with magnesium oxide, the sheath is vibrated to make sure it is tightly packed. The insulation is further tightened and packed when a cartridge heater is swagged.

Sheath

The two important functions of the sheath are to transfer heat to the material that is being heated and also serve as the container for the cartridge heater elements. When inserted, the sheath is in continuous contact with the material and results in efficient transfer of heat.

Different forms of alloyed metals are utilised in producing the sheath and also include Incoloy 800 and stainless steels 316 and 304. For specific applications, the sheath is corrosion and acid resistant.

Sealing

The sealing process is designed in order to seal and contain the contents of the cartridge heater. Once the MgO has been tightly packed around the core  and coil this part of the process is completed. A commonly used type of sealing material called epoxy allows the heater to pass different electrical tests to prevent shorts and ensure dielectric material performance.

Termination

There are large varieties of termination types that vary depending on the type of manufacturer and cartridge heater. With straight being the standard method, the leads could exit the cartridge heater in many different ways. In applications where the leads might be exposed to extreme heat or harmful chemicals, they are shielded with silicone or metal.

Termination Types

Lead Wire

The different types and kinds of lead wires differ based upon the conditions under which the cartridge heater would be used. The lead wire gives the electrical connection to the cartridge heater. Since the lead wire is necessary for the efficient and smooth operation of the cartridge heater, it is selected carefully in order to match the conditions and application. Fibreglass insulated wire is often used for high temperature cartridge heaters.

Anti-Seize Coating

The seizing of cartridge heaters creates multiple problems for operation efficiency and production. In case a cartridge heater seizes, it has to be removed by drilling it out of the hole if it gets stuck in the application, a process that could cause major delays.

The problem of seizing has led to the development of the split sheath cartridge heaters that help in expanding the hole in order to make contact with the material that is being heated. As the cartridge heater starts to cool, it retracts and can be removed easily.

Another way to avoid seizing is using an anti-seize coating that is applied as the cartridge heater is inserted. Anti-seizing coatings are a thermally conductive, insulating, and high temperature coating that improves heat transfer and minimises oxidation. It can be sprayed or brushed to form a thin layer that makes it easy to insert the cartridge heater into the hole.

Heatcon Sensors is an ISO 9001:2015 certified company and has been in operation for 30 years. Heatcon has received accreditation from certifying bodies like TUV SUD, DRDO CEMILAC, NSIC, and NABL. Production of heat sensing devices like Thermocouples and RTDs has been our forte! We also produce special sensors which find application in numerous industries including the ones specializing in aeronautics, railways, turbines, nuclear plants, and research labs.

 With over three decades of expertise in temperature sensor and heater manufacturing, Heatcon Sensors provides a high level of quality, accuracy, and an unbeatable commitment to customer support.

Uses for Cartridge Heaters

Cartridge Heaters have a lot of uses, but the most crucial function is to assist in the process of manufacturing by supplying localised heat. These cartridge heaters are designed in such a way that they provide optimum performance while also providing heat efficiently and accurately.

How effective a cartridge heater can be, is usually on the basis of a few factors like, the actual amount of heat that can be transferred from the sheath to the metal that is undergoing heating, its dielectric strength, and heat that is being transferred to the sheath. Dielectric strength is often calculated by the efficiency of the heater to retain electric current inside the coil.

Uses for Cartridge Heaters

1.Die Casting

During the process of die casting, a molten metal is initially placed inside a closed or open die so that the metal can be moulded into different forms and shapes. While the process of die casting is in progress, it is crucial to keep a track of the temperature of the metal and ensure that it is controlled and supervised. To accomplish this task, cartridge heaters are carefully positioned inside a hole in the die in order to accurately and cautiously control the temperature of the molten metal. In order to ensure that the quality of the final casting is at its highest, the entire process is meticulously regulated.

2. Mold Process

This process is pretty similar to the die process with some additional variations in the methods and materials being used. While talking about dies, it is important to keep a track of the temperature at which the heated metal solidifies. Cartridge heaters are inserted into the mold to help in controlling the process. During the process of solidification, the cartridge heaters are inserted into the mold to help in keeping the heat constant so that any kind of unevenness and weaknesses can be avoided in the molded part.

3. Food Production

The process of Food production also requires similar levels of control and accuracy as seen for the above processes of molding and die casting with the differentiator being, determining the accuracy during the preparation of food. Controlling heat becomes extremely crucial while preparing food, especially in the case of high volume food production centres, where an important criteria is to provide constant heat throughout a production run.

4. Medical

In the medical field, during the treatment of a patient, having the right control of heat is a very crucial factor in order to provide successful treatment. Several other medical processes also demand for exceptional heat control in order to assure success of the procedure along with safety of the patient. Cartridge heaters have been used in several machines to perform a variety of procedures that include kidney dialysis machines, controlling heat inside baby incubators, etc. In order to provide steady temperature and extraordinary heat transfer for different kinds of medical applications, cartridge heaters have been utilised in heating stainless steel or aluminium subassemblies.

5. Engine Block Heater

In frigid temperatures, Engine block heaters can be a reliable method to provide improved automotive performance. It provides efficient circulation of motor oil by warming engine fluids. Cartridge heaters are chosen among several varieties of block heaters because they are the easiest to install while also being the most effective. The coolant present inside an engine is heated quickly and efficiently due to the process of thermal induction used by the cartilage heaters.

6. Plastic Extrusion

The process of extrusion demands the molten plastic to undergo heating while simultaneously being forced through the mold by the screw. To help in having control over, and also providing constant heat so that the overall product is stable, cartridge heaters are included or installed in the extrusion process.The benefits of using cartridge heaters while performing the extrusion process include long service life and express warming.

With over 30 years of expertise in temperature sensor and cartridge heater manufacturing, Heatcon Sensors provides a high level of quality, accuracy, and an unbeatable commitment to customer support.

Cartridge Heater Types

Thermocouple Cartridge Heaters

Flanged Cartridge Heaters

Swaged Cartridge Heaters

Multizone Cartridge Heaters

Cartridge Heaters with Threaded Fittings

Cartridge Heaters with Split Sheath 

High Density Cartridge Heaters

High Temperature Cartridge Heaters

The different types of cartridge heaters depend on the type of applications, maximum temperature, overall length, watt density, tube diameter, heated length, and the variety of heating element being used. These factors help in determining the type of cartridge heater as well as how it is intended to be used.

The fundamental construction of most of the cartridge heaters is exactly the same regarding casing, wiring, and core. Variations will be observed in the kinds of metals, cores, and wires used. The durability and the associated quality of a cartridge heater is mostly dependent on the kind of materials that are used to manufacture it.

Cartridge Heater Types

1. Thermocouple Cartridge Heaters

Cartridge heaters that have a built-in thermocouple are utilised in heating the surface directly and their construction makes use of complex formulas to determine the fit, density, and wattage. The sheath temperature is measured by the internal thermocouple to determine the process temperature; internal thermocouple is ideal when there is a limitation in terms of available space. The sensor and power leads of the thermocouple are placed together on the outer side of the sheath. There are different varieties of thermocouple cartridge heaters, and they have been designed for specific applications. The thermocouple can be attached to the centre of the core, or at points along the length of the heater, or at the end of the heater. Based on the placement of the thermocouple, 3 styles of thermocouple cartridge heaters are available.

2. Flanged Cartridge Heaters

Cartridge heaters that have flanges make it possible to attach these kinds of cartridge heaters to the piece that is going to be heated. This is done by making use of a flange that is fixed permanently to the cartridge heater’s exterior end. This is done in order to make sure that the heater fits securely.

3. Swaged Cartridge Heaters

Prior to the swaging process, all of the elements including the oxide powder, resistance wiring, and the core are added to the heater. Mechanical swaging pushes the heater through a die thus reducing its diameter and also compacting  the interior components. This compacting process improves efficiency and enhances the heat transfer process.

4. Multizone Cartridge Heaters

When it comes to multi-zone cartridge heaters, a wound coil and power leads become an individual part of each and every section of the heater. There are two leads for every zone. In certain types of configurations, it is designed such that the zones will just have a common wire, and this would in turn act as one of the leads;  the individual sections can thus be controlled through this design. The advantage that the multi-zone system brings is that it gives us the ability to switch off a zone when it is not required; this in turn reduces the energy required.

5. Cartridge Heaters with Threaded Fittings

These types generally function similar to a flanged cartridge heater, threaded fittings help in providing the surety that the cartridge heater has been fit thoroughly. Threaded fittings give the luxury of faster installation and even speedy removal. Through the use of moisture seals protection enhancement is achieved.

6. Cartridge Heaters with Split Sheath 

Split sheath cartridge heater’s sheath is capable of expanding to increase its contact with the walls of the bore; this ensures maximum heat transfer and subsequently lesser power consumption.

The expansion of the sheath is achieved by eliminating the heater’s ceramic core, and in turn replacing it with magnesium oxide (MgO) that’s tightly packed around the heater coil. In doing so, the heater’s dielectric strength sees an improvement, and also better heat transfer is achieved. Split sheath cartridge heaters by nature of its construction have improved durability and have lesser failures that are the result of a bore seizure.

7. High Density Cartridge Heaters

High density cartridge heaters spread heat evenly over the casing of the heater and offer extraordinary power. They are built in order to withstand tough and rugged working conditions like expansion and contraction, vibrations, high temperatures, and shocks. Standard high density cartridge heaters have a cylindrical ceramic core around which a resistance wire is tightly wound. Room for more than one power zone is made available in a high density cartridge heater through the manner in which the resistance wire is placed.

8. High Temperature Cartridge Heaters

These kinds of cartridge heaters are designed with the goal of being able to withstand use in applications that involve very high temperatures; temperatures may range between 760°C and 870°C. Generally a lot of cartridge heaters that are used in high temperature applications are swagged, so that there is maximum vibration resistance and heat transfer. These types of cartridges are often used for sealing bars, hot stamping, heating platens, heat staking, and forming.

With over 3 decades of expertise in temperature sensor and cartridge heater manufacturing, Heatcon Sensors provides a high level of quality, accuracy, and an unbeatable commitment to customer support.