With the services of an Electrical Element Engineer at Win Technologies, you can be assured of professional technical backup in conjunction with our supply of EREMA Silicon Carbide furnace elements.
EREMA (Electric REsistance MAterial) elements are produced by TKK in Japan. TKK have been manufacturing since 1936 and have developed world leading element production technology. EREMA stand apart from other brands in consistent quality, fine grained low porosity elements. The result is a stronger element which is slower to age = less downtime and lower annual element replacement costs overall. Ask for our test comparison charts on strength and ageing characteristics.
Depending on type, most EREMA elements are supplied with new clamps and braids. This helps to ensure effective electrical contact, thus obtaining optimum element life.
EREMA elements are used in furnaces in the following industries :
- Laboratories – Coal testing / Analytical / Dental / Mineral
- Metal Heat Treating - Wire annealing / Automotive Spring / Gears/Sprockets /
- Mower and equipment blades
- Aluminium casting
D3 Type
Our heating elements consist of fine, dense crystals. Because of their improved oxidation and heat resistance, as well as enhanced strength, products of this type are most widely used as economical heating elements applicable in a variety of atmospheres at high temperatures. Depending on the application, appropriate coats to resist oxidation and corrosion are used.
E and F Type
The heating section has features equivalent to those of D3-type products. Modification of terminal sections was made to decrease their resistance to make these products an energy saving type with low heat loss from terminals.
SG-Type
Heating elements of this type have spiral grooves on their heating section and are given higher resistances to high temperature and corrosion than D-3, E and F type products so as to withstand severe operating environments. The inner part of products with larger diameters can be used as a tube type furnace. Terminal sections have been devised to provide low resistance, and have energy-saving properties as in E-type products.
SGR-Type
As in SG-type elements, spiral grooves are provided on the heating section with a terminal section on one side only. One side connection of the terminal allows for easier operation and facilitates construction of furnaces with energy saving structures. SG and SGR-type products are recommended for applications involving severe operating conditions including high furnace temperature ranges exceeding 1400 degrees Celsius.
U-Type
This type consists of two EREMA E (F) elements combined to form a U-shaped heating element. This is a single phase heating element with two terminal sections in one direction. With this product, furnaces of an energy saving construction can be built. Pin holes are optional.
Chemical properties
EREMA consists of stable high purity silicon carbide and surpasses metals in regards to high temperature, oxidation and corrosion resistance. When EREMA is actually used at high temperatures and comes in contact with gaseous atmospheres including water vapour, hydrogen, nitro-gen, sulfur or halogens, and molten alkali, alka-li salts (K2CO3, KC1, KOH, NaF, etc.), molten iron group elements (Fe, Ni, Co, etc.), and some metal oxides (CuO, Pb3O4, FeO, etc.), EREMA will react with them and can be affected by corrosion or oxidation.
Life Cycle
In general, silicon carbide heating elements are gradually oxidized to produce silica and thus so-called degradation occurs as its electric resistance increases more and more. Oxidation starts with heating element surfaces forming silica, an insulating material, resulting in increased electric resistance. This oxidation reaction begins at about 800 degress Celsius and is accelerated by increased temperatures. Electric resistance changes as shown in Fig. 2, and it is recommended to recognise that the expected life cycle limits for D3,E and F-types be recognised as having been reached when their electric resistance increases about three times higher than initial resistance (1.7 times higher for SG and SGR-types). The reason for this is that respective resistance values tend to disperse when their resistance approaches three times the initial value. In addition, heating distribution of each element is disturbed, leading to poor temperature distribution within the furnace. Moreover, it is necessary to pay enough attention to the life of silicon carbide heating elements since not only increased resistance but porosity changes or strength deterioration can contribute to breakage when their life approaches its limit. SG and SGR-types specificially, may easily alive at fusion late in their life. It should be noted that the life of heating elements varies significantly depending on operating conditions.
Operating Temperature
The life of EREMA decreases as its temperature rises. Especially, when furnace temperatures exceed 1400 degrees Celsius (D3, E, F and U) or 1600 degrees Celsius (SG and SGR), the oxidation velocity increases, resulting in reduced life. Therefore, it is desirable to use EREMA with its surface temperature as low as possible. This means that the difference between furnace temperature and that of EREMA should be kept as low as possible.
Surface Load Density and Limits
When surface load density (electric power) of EREMA increases, its temperature rises. The life of EREMA is reduced as its temperature increases. Even at the same furnace temperature, surface temperatures of heating elements increase with high surface load density.
Furnace Operation
Comparison of around-the-clock operation and intermittent operation of electric furnaces shows that the life of heating elements are increased in the former operation system. Silicon carbide heating elements generate silica coating resulted from surface oxidation of silicon carbide when they are used. Long term use allows gradual growth of this silica coating, followed by an increased resistance of heating elements. This silica coating develops abnormal expansion and shrinkage around the crystal transformation temperature (270 degrees Celsius). When the operation temperature goes up and down near this temperature, the coating is destroyed repeatedly, accelerating oxidation. Therefore, resistance may rapidly increase when furnace temperature happens to fall to room temperature in the event of power shutdown.
Connection
It is recommended that EREMA is connected in parallel. When dispersion exists in EREMA's resistances, a heating element with a higher resistance increases its resistance more and an imbalanced resistance distribution is encouraged if series connection is employed, resulting in accelerated ageing of the product.
Furnace Atmosphere and Materials to be processed
Furnace atmosphere and materials to be processed may affect the life of EREMA. For further information, please contact us. Within the furnace atmosphere, it is recommended to keep surface load density as low as possible.
List of Coatings available for applications described below-
For D3, E and F-types EREMA products, a variety of coats can increase their life by preventing them from ageing against a special atmosphere or corrosive materials. Incorrect selection of coat materials may result in adverse effects.
 |
|
| U-Coat: |
Characterised by its oxidation resistance, widely used for general high temperature applications and specifically effective against water vapour.
|
| L-Coat: |
Modification of U Coat. Water vapour atmosphere resistance is further upgraded.
|
| H-Coat: |
This coat shows its effectiveness in alkali atmospheres and is used on heaters for float baths.
|
| S-Coat: |
This coat is effectively used for melting and heating optical glass which contains metallic elements.
|
| N-Coat: |
This coat is specially developed to be resistant to a N2 atmosphere. It is effective in a N2 atmosphere under conditions in which furnace temperatures do not exceed 1450 degrees Celsius and surface load density is less than 6 W/cm2 |
| |
|
Clamps and Straps
