Cartridge type tubular electric heating elements
The necessity of local heating of a metal equipment details arises more and more frequently in present-day industry. One-end heaters, the invention, which is widely applied now, has become the solution of this problem (making of contact outputs on one side of the heater is the peculiarity of such heaters).
The said heaters, made of stainless steel, have become the reliable machine parts.
Sphere of application
Cartridge type tubular electric heating elements (often called finger tubular electric heating elements) may be used not only for metal heating, but also for the heating of water and oil, diluted solutions of acids and alkali, air. At present cartridge type tubular electric heating elements are widely used not only in industry and in the production process (in molds, thermoplastic automatic machines, they are often used on moving components of machine parts). They are frequently used in domestic heating appliances.
Arrangement. Cartridge type tubular electric heating elements
D – diameter of shell
L – developed length
Lk – contact core length in termination
Tubular electric heating element consists of a stainless tube with polished surface (which ensures very tight contact with the heated object) hermetically welded on the one side and wires protruding from the other side; inside (centrally located) the stainless tube is the spiral of high resistance material. The spiral is insulated from the inner wall of the tube by compacted electric insulating filler with high thermal conductivity. The spiral is wound on the core with a certain winding pitch (pitch of the wound spiral depends on capacity and voltage of the heater). Manufacturing technology prevents possibility of short circuit between the spiral turns. To prevent penetration of moisture inside the heater the end face of tubular electric heating element with contact wires is sealed with a special compound preventing penetration of moisture. Thus, cartridge tubular electric heating element is completely sealed and, therefore, protected from the effects of the environment which has an important effect on service life of the heater.
Operation of cartridge tubular electric heating elements.
In the result of passage of current in the spiral of tubular electric heating element heat energy is “produced” moving from the tubular electric heating element center further to its shell and on to the heated body. Service life of tubular electric heating element depends directly on observance of the provisions of operating rules.
As cartridge tubular electric heating elements are used for heating various environments (starting from metals and ending with air) it is important to understand clearly when ordering and manufacturing the electric heating element for which exactly environment such cartridge tubular electric heating element is intended. Each environment to be heated permits to design electric heating element with a certain wattage per square centimeter (maximal load for electric heating element may attain 15 watts per square centimeter), it is prohibited to use the cartridge electric heating element in the environment for which it is not designed. Otherwise the electric heating element will burn immediately; it is also prohibited to exceed the permissible load on the square centimeter, for in such case service life of the electric heating element will be considerably reduced. It is important to know, that in the process of operation electric heating element must be in close contact with the heated surface, it is especially important in cases of heating with cartridge electric heating elements of metal, in such cases clearance between the electric heating element and the heated surface must not exceed 0.08 mm, for presence of air between the electric heating element and the heated body leads to local overheating of the electric heating element and its filler which reduces service life of the heater considerably.
Cartridge electric heating elements. Operating conditions.
- working environment temperature up to 300C
- relative air humidity up to 65% at 20C
- non-explosive environment with permissible content of aggressive gases.
We produce cartridge electric heating elements with the following technical parameters:
Length 40 – 6000 mm
Diameter 6.3 – 32 mm
Cartridge tubular electric heating elements are manufactured for nominal voltages 12; 24; 36; 42; 48; 127; 220; 380 volts
Length of cold section up to 30 mm
Length of heat resistant wires is made to customer’s order (standard length 25 cm),in customer’ request heating element can be equipped with rigid terminals – pins instead of wires.
In accordance with work specification cartridge heating element can be equipped with mounting fixture in the form of a union of required diameter connected with the heating element’s shell by welding, soldering or molding.
We produce angular type cartridge tubular electric heating elements according to customer’s drawing.