Heating principle and control point of electric heater

The Joule effect of current is used to convert electrical energy into heat to heat an object. It is usually divided into direct resistance heating and direct resistance heating. The power supply voltage of the former is directly added to the heated object. When the current flow is overdue, the heating of the electric heating and ironing machine is heated by the heated object. An object that can be heated by a direct resistance is necessary for a conductor, but has a higher resistivity. Because the heat occurs in the heated object itself, the heat is attributed to the internal heating, and the heat efficiency is very high. Direct resistance heating should be made of special alloy or non-metallic materials. The heating element will generate heat through the heating element and transmit to the heated object through radiation, convection and conduction. Because the heated object and the heating element are divided into two parts, the variety of the heated object is usually not restricted, and the operation is simple.

The data used by heating elements of direct resistance heating are usually with large electrical resistivity, small resistance temperature coefficient, small deformation at high temperature and not easy to embrittlement. The metal data such as iron aluminum alloy, nickel chromium alloy and other non-metallic materials such as silicon carbide and two molybdenum silicide are commonly used. The highest operating temperature of the metal heating element can reach 1000~1500 C according to the data, and the maximum operating temperature of the non metal heating element can reach 1500~1700. The equipment facilities, heat furnace replacement, but it needs work pressure regulating equipment life than alloy heating element is short, usually used in high temperature furnace, the temperature data beyond the metal heating element of the highest operation temperature and promised to local some special occasions.

The electric heater control system in detail key:

Electric heater for resistive heating, the appearance of mode is a flange type electric heater.

The electric heater is composed of two series horizontal heater device, device for support leg device, select "delta" connection.

After power supply to the electric heater, it makes it hot, and then heat the active medium in the container, and make the medium reach the set temperature value at the outlet.

The electric heater is controlled by the temperature control table ST1. After collecting the outlet temperature signal by ST1, after PID is controlled, the output signal of a 4-20mA is output to the SCR trigger module, then the output power of the heater is controlled, and the stepless power regulation of the output 0-400kW is completed.

The appearance of ST2 internal temperature alarm detection heater 6 temperature, when the flow rate is too low or no flow and other reasons, the heater showed dry conditions, at any point within the temperature beyond the surface within the temperature setting value control circuit and alarm lock, with alarm lamp. Then it is necessary to reset the heater manually, and the heater can be restarted.

The system has a pressure alarm chain system. The operation of the control cabinet is interlinked with the user's system pressure. The chain signal is supplied by DCS. As long as the medium pressure is in normal condition, the heater can promise to start.

During the process of heater re operation, when the SCR is generated because of the over temperature, over current or lack of integrity of the thyristor, the heater will be blocked and the alarm signal will go to DCS.

The body system has a number of chains, and can be used with other equipment for chain use, do not have to ask for short connection.