Bearing heaters use heat to ease the assembly or disassembly of bearings and other machine components. The inner ring of the bearing is heated, which results in thermal expansion and allows the bearing or gear to be mounted or dismounted easily without any damage.
One can use many different heating methods, such as conduction, convection, and radiation, which are the main types of heat transfer, with more complex thermodynamics based on these three basic principles. Various heat transfer methods are used commercially in the manufacturing process to vary the electrical resistivity, magnetic, and physical properties of metals by using different techniques. Induction heating is however quite popular in heating bearings during mounting and dismounting.
In the induction heating process, an electrically conductive material such as a metal is heated to change its physical properties, such as diameter, without the material coming into contact with the inductor. Heat is induced to the conductive material when the electric current circulates around it, as it is placed within a magnetic field.
For the induction heating process, the material can be placed farther away from the power source. This method ensures efficient and steady heat transfer with low heat loss. Therefore induction heating is useful for all the processes where a direct flame is not desirable.
A typical induction heater consists of:
The power supply source should be able to provide alternating current to the work coil.
The material to be heated is placed inside the coil. The induction work coil is often air or water cooled and does not need to touch the object material. A power supply is used to convert direct power to alternating current of the desired voltage.
An electronic oscillator sends a high-frequency alternating current to the electromagnet. The coil receives an alternating magnetic field. This magnetic field transfersinto the material, or conductor set up for heating. An electric current, also known as an eddy current, is produced in the material. These eddy currents encounter material resistance which leads to the heating of the material. This process is known as Joule heating. Ferromagnetic metals like iron or steel are heated up by magnetic hysteresis losses.
The high electric current frequency can vary depending on the type of material to be heated, the depth necessary for heating, the coil and conductor connection type, and the size of the object.
The rate at which the material heats up depends mainly on its resistivity to the eddy currents. If the resistivity is high then it produces more heat as the current is passed through it. On the other hand, a material having low resistivity causes it to produce less heat and therefore the temperature rise will be slower.
The heat generated in the material depends on the coil current, the number of turns of the coil, the frequency of the current, and the resistivity of the material.
If the bearing is positioned correctly, then the induction process is smoother and better controlled. During the process, the induction heater itself does not heat up as the heat is generated only in the bearing.
Specific heating devices are specially designed for pre-heating batches of small bearings before mounting. The temperature of the plate can be adjusted to provide temperatures between 120°F and 390°F.
There are induction heaters designed to heat roller bearings that can be mounted onto a shaft. Heating the bearing causes it to expand, which eliminates the need to use force during installation. Generally, using these devices generates over 160 °F temperature difference between the bearing and shaft is sufficient to enable installation.
Some devices are manufactured in glass-fiber and other heat resistant material that allows a low-temperature difference between the inner and outer rings of the bearing. This helps to reduce internal tensions that are generated due to excessive thermal expansion of the inner ring compared to the outer ring.
Industry demands for precision and quality are increasing day by day. If you want to be sure that the temperatures are accurate, then these devices must be regularly calibrated. This calibration should be carried out once a year. Mainly the calibration is in the temperature measuring sensor in the induction device which ensures that the device provides proper heating to the bearing so that it attains the correct temperature in desired time.
e2b calibration provides reliable and cost-effective calibration services for your bearing induction heaters. Our verifiable and traceable services are unmatched in the industry. We are ISO-17025: 2017 compliant and registered with ANAB. We are also ANSI/NCSL Z540-1-1994 certified. We are NIST Traceable Wide scope of ISO/IEC 17025 accreditation. Contact e2b calibration for more information about our on-site calibration services.