Nine processing processes of tubular heater
The manufacturing process of tubular heater is mainly divided into the following steps: pipe making, wire winding, welding, filling, rolling, annealing, bending/pressing, sealing, inspection/packaging.
Tube making: Tube making is the most basic process in the preparation process of tubular heater.
The tube making machine mainly makes steel strips of different materials into metal outer tubes of tubular heater. Pipe making machine is a set of processing system specially designed for tubular heater to produce outer tube, which can be finished from steel strip, through preliminary molding, then welding, and rolling to the required diameter, and then a series of processing processes such as cutting off and straightening.
Winding wire: the resistance wire is the core component of the tubular heater, which needs to be wound into a spring shape to improve the heating capacity per unit tube length. Winding resistance wire is completed by a special winding machine. The wire winding machine wraps the straight resistance wire into a spring shape, and then cuts it off according to the required winding length for the next process. The shape and size of resistance wire winding and the type of resistance wire used will greatly affect the performance of tubular heater.
Welding: in the tubular heater, the resistance wire needs to be connected to the external circuit through the lead-out Rod. In actual production, the resistance wire and the lead-out Rod are connected by welding, and this process is completed through the resistance wire soldering machine.
Filling: magnesium oxide powder is an important part of tubular heater, which mainly plays the role of insulation and heat conduction. In the production process, magnesium oxide powder is filled into the metal tube which has been built in and positioned with resistance wire through filling machine. During the filling process, the resistance wire must be kept in the center, and the magnesium oxide powder must be filled tightly.
Rolling: rolling is to compact magnesium oxide powder to ensure the highest heat conduction efficiency between the resistance wire and the external environment, and at the same time to ensure that the resistance wire is on the axis of the metal tube.
Annealing: rolling through the cold processing mechanism to make the outer tube molding, This molding will lead to the metal surface structure cold work hardening and grain refinement, forming dense fiber, and forming residual stress layer, the processability of the material is affected. In order to make the tubular heater obtain good bending performance, annealing treatment is usually carried out to eliminate residual stress, and the mechanical properties of the annealed metal outer tube will be obviously improved.
Bending/pressing: in many application scenarios, straight tubes cannot meet the requirements, and tubular heaters need to have different shapes to adapt to special applications. The straight pipe is bent into the desired shape by a bending machine at a specific bending point, angle and bending radius. After that, the tubular heater is pressed at the bending place with smaller size to eliminate the negative impact of bending on the performance.
Sealing: sealing can improve creepage distance and electrical performance of tubular heater. The sealing of tubular heaters can be divided into complete sealing and incomplete sealing. The fully sealed tubular heater is sealed with epoxy resin and is suitable for heating liquid. The tubular heater with incomplete seal is sealed with silicone oil + silica gel, which is suitable for heating gas.
Inspection/packaging: including resistance value test, electrical insulation test and thermal dielectric strength test, etc.