Miller Induction Heating - How it Works
by Admin
Posted on 21-06-2023 12:37 PM
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miller induction technology boosts productivity, reduces hydrogen cracking in pipeline applications
induction technology provides a fast, safe and consistent heating method for pre- and post-weld heat treatment, to help minimize the risk of weld failure due to hydrogen-induced cracking in high-strength steels. The proheat 35 is an air cooled induction system for preheat applications up to a maximum preheat temperature 204°c (400°f)
the proheat 35 liquid-cooled system can be operated in manual programming mode where a power output is applied to a part for a specified time or in the temperature based programming mode where the part temperature is used to control power output.
Pre-heating of a valve body to 400°f before welding on a repair. Water-cooled induction coils (miller patented) are flexible and easy to apply to a variety of geometries. Here a “pancake” style coil has been wrapped around a repair area. Typical heat time for this application is 10-15 minutes for both the inside and outside of the body to be at temperature. Note also that this coil is protected with pre-heat covers to protect the coil from hot weld slag and abrasive wheels. Because the heat is in the valve and not the coil, rope, plastic tie wraps and tape can be used to hold the coil into place.
Applications that would typically require hours to heat can be done in minutes utilizing induction heating. In addition to the simplicity and efficiency, the miller proheat™ 35 induction heating system solves many key issues in today’s environment: does not produce the exposure to burns associated with open flames and electrical resistance wires (only the work part becomes hot) no significant expense of fuel gases. Produces fewer fumes than flame heating. Produces less particulate from overheated insulation caused by high temperature electrical wires and ceramic pads. Induction heating is a simple, cost-effective heating process that delivers fast and consistent heat in the following applications and industries:.
Go Beyond Flame Heating: ProHeat™ 35 Induction Heating System
With the use of more thin-wall steel alloy pipes in today’s oil and gas pipelines, manufacturers and installers are turning to the fast, accurate and uniform heating of induction heating systems. During the process of butt welding, induction heating is commonly used to preheat the joint area to 150-200 °c to prepare the area for a consistent quality weld. After welding, the joint area is heated to 600-650 °c for thermal stress relief of the weld area. Traditional gas flame and resistance. Heating systems are often impractical when these higher temperatures are required.
Not only are they too slow to meet the cycle times demanded by the industry, but also the heating can be inaccurate and can lack uniformity around the full circumference and bandwidth of the weld joint.
Preheating involves heating the base material or at least the area surrounding the weld joint to a specific temperature before welding. When preheat is required, the minimum temperature is part of the welding procedure specification (wps). Induction heating systems employ non-contact heating. They induce heat electromagnetically and through hysteresis. Heating tools are placed on or around an electrically conducting object, and the magnetic field creates eddy currents inside the part, exciting the part's molecules and generating heat. As a result, the workpiece itself is the source of the heat, not the heating tools. Compare this to two other common methods for preheating: resistance and open flame.
Miller Induction Heating - Where it Works
Induction heating has been successfully used in industrial and construction welding applications, including refineries, petrochemical, pipeline, structural, shipbuilding, pressure vessel repair and mining. It is mainly used for preheating - to minimize the temperature difference between the arc and the base material. Image courtesy - miller welds preheating slows the weld cooling rate and allows hydrogen to escape the weld puddle — two factors that help reduce the risk of cracking and the potential for a failed weld. When preheating or post-weld stress relieving are necessary, induction can save significant time and provide temperature consistency up to 1,450 degrees fahrenheit or 787 degrees celsius.
Induction heating makes use of the induced current by the electromagnetic induction in the charge to be heated. The induction heating works on the principle of transformer action, in which the primary winding which is supplied from an ac source is magnetically coupled to the charge, to be heated, which acts as a short-circuited secondary of a single turn. When the ac supply is connected to the primary winding, it induces currents in the charge. As the secondary, i. E. , the charge has some resistance, thus the induced currents in the charge heats it up.
Especially for preheating of welding seams leifert induction has developed a flexible, air cooled induction coil. Excellent mechanical features coupled with fireproofed materials build a special tool in the area of welding.