This article contains everything you need to know about band heaters and their use.
You will learn:
A band heater is a heating device that clamps onto objects to provide external heat using radiant and conductive heating. The different mounting methods of band heaters makes it possible to secure them tightly and firmly such that they do not shift or loosen. The three main types of band heaters are ceramic, mineral insulated, and mica, which are further categorized by their type of insulation, mounting, dimensions, termination type, sheath or sleeve, and performance.
The wide use of band heaters is due to their ability to rapidly provide indirect heat to an application. The selection of the type of band heater is dependent on the type of insulation of a band heater and the application for which it is used with mica being the most commonly used while ceramic band heaters are ideal for mid-temperature heating.
The uses of band heaters take several forms, which change in accordance with the shape of the object to be heated. While it may be presumed that band heaters are mainly used with pipes and tubing, they are also used for heating barrels or drums of fluids and liquids as well as buckets and dies for extruding. They are a convenient and adaptable way to rapidly heat and prepare materials.
Although there is an endless number of band heaters, there are various aspects of each type that are common to all band heaters and are a characteristic of their use. The main common trait of all band heaters is their shape and clamping mechanism. They receive power from an electrical supply that supplies current to their heating element through terminations that extend from a band heater. Heating elements are chosen for their high resistance wire that generates heat that is passed to the object being heated.
An essential part of a band heater is its heating element, which converts electrical current into heat through the process of resistance, known as Joule Heating. As electric current passes through the element, it faces resistance. While conductors are good carriers of electricity, insulators are not and offer high resistance to electrical current. The increase in resistance produces heat that is spread by conductors.
According to Joule Heating, when electric current flows through solids or liquids that have limited conductivity, the electrical energy is converted into heat by resistance losses in the material. The heat that is generated is very small and happens when the conduction electrons collide with the conductor’s atoms. Joule heating is regarded in two ways. In applications where heat is needed, such as a band heater, Joule heating is desired and part of the process. The generated heat from Joule heating is unwanted in electronics, power lines, and fuses since heat can cause them to degenerate.
There is a long list of the types of heating elements that are used with band heaters and include metal, ceramic, thick film, and polymer PTC heating elements. Resistant wire heating elements include ferromagnetic, copper nickel alloys, etched foil, and nichrome, which come in the form of wires, ribbons, or strips. Metal heating elements are very commonly used with band heaters with nichrome being the most used.
Other forms of heating elements include molybdenum disilicide, silicone carbide, PTC ceramic, and quartz halogen. Polymer PTC heating elements are made of conducting PTC rubber that rapidly heats up when activated. Thick film heating elements are printed on thin substrate and have a very low profile, which allows them to provide a quick thermal response.
The sheath, also referred to as a jacket or sleeve, for a band heater is its outer cover that protects the heating element. They are made from a wide assortment of metals including aluminum, brass, copper, iron, nickel alloys, steel, and stainless steel. The sheath has to be highly durable in order to withstand the environment where a band heater is used and the heat generated by the heating element. It surrounds the heating element and acts as a conductor during the heat transfer process.
As with other factors of a band heater, the sheath can take several forms and can be rectangular. Its performance is benefited by the type of insulation, which prevents heat loss. Of the various forms of sheaths, stainless steel is widely used and highly recommended due to its resistance to the effects of rust and high temperatures. A unique form of sheath is a perforated air cooled metal sheath for enhanced surface area exposure.
The basic forms of insulation for band heaters include ceramic materials, mica, fiberglass, and mineral insulation. Certain forms of band heaters are manufactured without insulation due to their low profile but are not energy efficient. Uninsulated band heaters were the first form of band heater and are still used to heat barrels.
As with all aspects of band heaters, the clamping styles vary widely and include straps, barrels, welded barrel nuts, and spring-loaded types. Specialized forms of clamps are engineered for rapid attaching and removal to limit delays in production.
The variations in clamping methods are associated with proprietary manufacturing techniques and designs. The five listed above are the most common but are only a sampling of the types of clamps that are available.
Insulation band heater jackets are insulation covers that can be placed over band heaters as an extra layer of insulation and protection. They fit easily over a band heater and can take any shape to fit the needs of the band heater and the application. The primary reason for the use of insulation jackets is for lowering cost due to heat loss. Insulation jackets make it possible for band heaters to cycle less, which lowers their consumption of electricity. They establish a thermal barrier to stop the dissipation of heat and focus the heat at the item being heated.
The various structures of insulation jackets include layers of silica glass fibers, braided stainless steel cloth, ceramic fiber, or aluminum cloth with a protection layer made of glass fiber, Teflon cloth, or stainless steel cloth. In most cases, the thickness of an insulation jacket is customized to meet the needs of the type of band heater and its application with standard thicknesses being between 0.2 inch up to 6 inches (5 mm up to 150 mm) with a temperature resistance up to 1832°F (1000°C).
Each half of a two-half band heater is rated for 120 V. They are wired in parallel for 120 V operation or in a series for 240 V operation. Electrical connections are post terminals or insulated stainless steel over braided leads. Terminal boxes are normally included to protect workers from electrical shock and electric shorts. In addition, disconnect plugs are available with clamping variations to eliminate exposed terminals and wires.
The wiring of a band heater varies depending on whether the electrical source is two or three phase. Dual voltage designs have 3-wire parallel circuits for dual voltage applications. Three phase wiring is used for very high wattage band heaters to reduce current load across the conductor. Terminal lugs are used for safe, fast, and easy attachment of wires to a band heater.
The initial categorization of band heaters is by the types of insulation they use, which are mica, ceramic, mineral, fiberglass, and various other forms of insulation. They are further categorized by their dimensions, type of mounting, installation, termination types, sheath material, and specifications. There is an endless number of band heaters that have been developed and perfected to meet the needs of several applications.
The standard and most common form of band heater is a ring that clamps on the outer diameter of a pipe or tube. Their varying sizes makes it possible to place a band heater around any form of cylindrical object. As with the structure of band heaters, the maximum level of heat they provide also varies and must be carefully watched to ensure a chosen band heater meets the requirements of an application.
Ceramic band heaters have spiral wound resistance wires that are threaded through the blocks or tiles of ceramic material. The tiles are placed beneath the sheath, a construction of the band heater that gives it flexibility and efficiency to the conduction and radiation of heat. The coils of wire pass heat evenly through the ceramic tiles which radiate the heat to the object being heated.
The ceramic insulation that is built into a band heater ensures an even distribution of heat and is not affected by irregular surfaces or a loose fit. Since heat transfer is completed by radiation, conduction, and convection, ceramic band heaters are perfect for heating pipes or tubes.
Mica band heaters use an assortment of alloys for their element wire and have various layers of mica for ease of heat transfer. They are available as a one-piece construction that is perfectly round or two-piece construction with the core and wires bent together to form a single band. Mica band heaters are widely used where control of the temperature is necessary, and lower maximum temperatures are required.
The corrosion resistance and dielectric strength of mica band heaters makes them ideal for harsh and stressful environments. Since they are not able to achieve excessively high temperatures, they are less expensive than other types of band heaters and are flexible and adaptable to meet the needs of any set of conditions.
Mineral insulated band heaters, or MI band heaters, are used for extremely high temperature applications that can exceed 2000°F (1094°C). Regardless of their high energy capabilities, they are used for applications with temperatures that range around 1400°F (760°C). Mineral insulated band heaters have high wattage density, the amount of heat concentrated in a square inch of surface area. The material used to produce mineral insulation is compacted magnesium oxide that is used to coat a band heater. The choice of mineral insulation is due to its exceptional thermal conductivity.
The various types of MI band heaters are known for their ruggedness and durability in heavy duty applications. They are used to increase output in injection molding since they meet the specifications to process high tech resins. The nichrome resistive wire inside the MI insulation is embedded in aluminum oxide for excellent heat transfer and dielectric strength.
Aluminum band heaters are known for their exceptional thermal conductivity and are used for applications requiring high watt density. They have tubular elements that are extruded into an aluminum case and can reach temperatures of 650°F (343°C). The direct contact of an aluminum band heater with a uniform sheath temperature allows for quick response and precision heating. Unlike other forms of band heaters, aluminum band heaters have a low expansion rate, which makes it possible to draw them tightly to the piece being heated.
The uses of aluminum band heaters include heating barrels of plastic extruders, injection molding machines, heating dies and die heads for extruders, and heating blow molding equipment. Their rugged design with excellent heat transfer makes aluminum band heaters contamination free and easy to install.
The tubular elements for an aluminum band heater are placed in an extruded aluminum base, which is sectioned for positive contact. Special versions of aluminum band heaters are able to provide both heating and cooling and have cooling tubes placed next to the heating elements. Since an aluminum band heater has low mass, it can cool rather quickly for efficiency.
Tubular band heaters, known as sheath or tubular elements, have a metal sheath with a resistant wire coil placed in insulating material, which is normally mineral insulation made from magnesium oxide. The design of tubular band heaters is unlike that of other types of band heaters in that they are in the shape of tubes that can be shaped to fit any type of heating application.
The adjustability of a tubular band heater makes it possible to fit it with different terminations and mountings, which allows them to be designed for different electrical ratings, diameters, and heater lengths. Their high watt density allows for efficient heat transfer regardless of the type of medium. The simple structure of tubular band heaters gives them high durability and long service life with very little need for maintenance.
Nozzle band heaters are a smaller version of typical band heaters with a diameter of 3 in (76 mm) or less. As with all types of band heaters, nozzle band heaters are available in one- or two-piece versions with different diameters, widths, voltages, clamp styles, and connections. Nozzle band heaters are equipped with ceramic, mica, or MI insulations with a maximum watt density of 40 W/in² (6 W/cm²) and maximum temperature range up to 850°F (454°C). Even though they are much smaller than typical band heaters, nozzle band heaters can be designed with cutouts, holes, and slots to go around any obstacles.
The small size of nozzle band heaters allows for fast heat up. They slip easily over a nozzle with tabs that draw them tight using bolts and nuts. Leads for nozzle band heaters come in various forms and are projected away from the heater by braided cables. Working with nozzle band heaters requires care and proper attention to ensure the safety of personnel.
Rectangular band heaters are manufactured in the same way that circular band heaters are but have a rectangular shape. They are used for heating rectangular dies and molds that circular band heaters are unable to fit. Rectangular band heaters are one or two-piece band heaters that are produced with specific dimensions for the lengths of their sides and widths. In most cases, they are special ordered with the required lengths of sides, wattage, and voltage.
Screws are used to connect the halves of two-piece rectangular heaters and are used to seal one-piece rectangular heaters. In some designs, the electrical leads are connected to the screws using lugs. Other forms of connectors include plugs and connection boxes and depend on the shape and design of the heater.
Each band heater has multiple types of terminations available in order to meet custom designs. Termination choices include leads, stainless steel braid, and post terminals that have flexible screw terminals, plugs, caps, pipe couplings, copper elbows, and terminal boxes.
The term terminations refers to the type of electrical connection a band heater may have with post terminal connections being the most secure. Included in the types of terminations are plug, block, metal, and horizontal and vertical posts.
Thermocouples, known as a thermoelectric thermometer, are used with band heaters to measure temperature. They have electrical conductors that form an electrical junction. The most common types of thermocouples are types J, K, T, E, and N with types J and K used with band heaters.
Barrel or drum band heaters are one of the methods used to keep the contents barrels heated and are used for viscosity control, freeze protection, temperature maintenance, thermal mixing, and melting of solids. The structure of barrel band heaters is the same as the other types of band heaters with heating elements inside a metal sheath. They can be used with metal and plastic barrels and come in various styles to meet the needs of an application.
Thermostat control barrel band heaters enable users to set the temperature for the heater. When the band heater reaches the set temperature, it maintains the temperature. With pre-set thermostat barrel band heaters, the manufacturer sets the temperature. Variable control barrel band heaters allow the user to set the temperature of their choice, which can vary according to the needs of the application. Water reduction and reduction barrel band heaters are used with materials that can burn, separate, or be charred.
The distinguishing characteristics of barrel band heaters is their toughness, strength, durability, and ruggedness, which enables them to endure the many types of environments they have to confront. The temperature range for barrel band heaters vary in accordance with the type of barrel or drum and its contents.
The variations between one- and two-piece band heaters are their diameters and their structure with one piece band heaters being one sheath with insulation while a two piece is two pieces of sheath and insulation. Both types of band heaters come in a wide variety of shapes and sizes. Clamping is different between the two types with one-piece band heaters having a single form of clamping while a two-piece band heater has clamping on two sides.
The performance and capabilities of both styles is the same with the only variation being their design. Although one-piece band heaters can be opened and expanded to fit around the object to be heated, some versions have hinges to make installation easier for hard-to-reach places.
Band heaters are an efficient, flexible, and durable solution for providing heat to a wide range of applications in various industries. With excellent thermal conductivity and exceptional insulation, they are an ideal source for heating equipment, solutions, and processes. Since their introduction, band heaters have become an essential part of heating processes for industrial applications.
The main reason for the popularity of band heaters is their exceptional thermal conductivity, which allows them to transfer heat evenly over the surface of the object being heated. It is an efficient heating process that works quickly and operates at high temperatures.
A key to the universal success of band heaters is their ability to distribute heat evenly and uniformly over the object being heated. For many applications and processes, this is essential and critical to the success of a process. Heat is distributed across the entire surface of an object, which is essential for applications that require precision temperature control.
The flexibility of band heaters enables them to be installed on a wide range of surfaces using the many different types of clamping methods. The process for installation is carefully calculated for precision positioning of a band heater such that it provides heat in the proper location. Many manufacturers provide custom installations for applications that are outside the normal range of traditional band heaters.
The many environments where band heaters are used require band heaters to be durable, strong, capable of withstanding stress, and resistant to the effects of materials in the atmosphere. As with all forms of industrial equipment, band heaters are heavy duty pieces of equipment capable of enduring the most stressful conditions. The fact that they are a heating device further indemnifies the need for them to have exceptional strength.
Of all of the many tools used to produce products, band heaters are the most customizable due to the nature of their process. Sheaths can be changed. Heating elements can be adjusted, and there are any number of types of insulation materials. The key to customizing band heaters is their voltage, wattage, and wattage density, which can be adjusted for the needs of any application or special conditions.
The many uses for band heaters is rapidly rising as new technological advancements are adding new and intricate products to the market that require control, precision, and proper heating. The range of industries that require controlled heat for heating parts and components are endless and a fundamental part of industrial processes.
In plastic molding, band heaters are used to heat and mold plastic materials. The key factor in their use is the precision control of the heating process, which ensures the proper level of heat for shaping a product. They help soften materials for proper shaping.
As every chef can tell you, proper heating is an essential for preparing food in order to reach the proper consistency and flavor. Band heaters help heat ingredients to the correct temperature for mixing and assist in maintaining the temperature. Since band heaters are able to provide constant even and uniform heat, they help ensure that food is cooked and heated evenly.
A common use for band heaters in packaging is sealing and shrinking packaging materials such that items to be shipped are held tightly in place. Since band heaters heat up quickly, they are ideal for the process due to the many packages that have to be handled at once.
The use of band heaters in the pharmaceutical industry is very similar to their use in the food industry since temperature control is critical to the production of medicines. Precision temperature control helps produce uncontaminated medications that have the proper consistency and texture.
Drum band heaters are used by chemical processing to keep chemicals at a desired temperature. They help reduce viscosity, help with heat transfer, and keep liquids in liquid form.
The heating of industrial equipment is a common use for band heaters due to their flexibility and ease of installation. They are used to regulate chemical reactions, maintain viscosity, and prevent freezing in storage tanks, reactors, pipes, and processing tools.
The use of band heaters for metal casting is very similar to their use for plastic forming or injection. They are used to heat molds, keep materials heated, and help casting tools reach the appropriate temperatures for pouring molten metals.
Although the installation of a band heater is uncomplicated due to the nature of the device, there are several steps to be taken to ensure proper installation and proper performance of the device. The initial step in the process is a close examination of the location where the band heater will be installed. The surface upon which it will be placed should be even, smooth, and uniform for proper transfer of heat. A high temperature thermal compound may be necessary to cover any pits, holes, or divots in the surface.
Clean the surface of any contaminants that will interfere with heat transfer. Such materials can shorten the life of a band heater and inhibit its performance.
Securely seat the heater such that it is not shifting or floating over the object to be heated.
Once it is determined that the band heater is properly seated, it can be clamped into place using the clamping method designed for the heater.
This step of the process can take several forms depending on the types of leads connected to the band heater. The easiest and most obvious form of band heater termination is plug in, which is used in certain types of band heaters. Other connections can be two, three, or four wire connections.
Once the band heater is properly seated and wired, it is time to test it to see if there are any difficulties. During testing, the heater should be allowed to reach its maximum temperature.
At the end of the initial power up, the band heater should be powered down in order to tighten down the heater due to elongation caused by thermal expansion. This should be completed while the heater is still hot.
Testing a band heater should be a regular part of industrial operations to ensure a band heater is providing optimal performance. During installation, a band heater is normally tested to ensure a tight and firm connection of the heater to the object being heated. After installation, it is a good practice to regularly test a band heater. The steps to the process are:
Band heater manufacturers provide data and information regarding band heater performance and have experts on call to assist in determining the effectiveness of a band heater.
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