Type SPIRAL double element

TYPE DOUBLE SINGLE ELEMENT

Made of special high-density reaction-bonded silicon carbide, the SER SIC TECH® is a tube with both electrical connections on one end. The hot zone is formed by cutting a double spiral slot which reduces the cross sectional area through which current flows, resulting in higher resistance than the cold end. The cold end is formed by cutting two longitudinal slots along the length of the tube. The SER element is supplied with a ceramic collar cemented to the extremities of the cold end. The cold end of the SER element is flame sprayed with aluminum for a distance of about two inches. Flat braided-aluminum straps are held in compression with stainless steel clamps to this metallized area. The clamp is electrically insulated from the flat braid with high temperature insulation. The aluminum braid is 10 inches (254 millimeters) long and holes are provided for easy connection to the power supply.

MOUNTING

SER SIC TECH® can be mounted vertically or horizontally. When mounted horizontally, the hot end does not need to be supported. When mounting the element horizontally the slot in the terminal end should not come in contact with the insulation in the wall of the furnace or kiln. This is most easily accomplished by placing the slot in a horizontal position. The terminal holes should also be 10% larger than the diameter of the element. Extreme caution should be used when mounting to ensure that the SIC TECH® are not placed in tension. There should be adequate freedom to allow for the furnace and SIC TECH® to expand and contract independently.

SIC TECH® should have their heating sections centered in the furnace chamber so that no portion of the heating section extends into the furnace wall. A conical or truncated cone shaped recess 1/2 inch (13 mm) deep is sometimes located on the interior wall where the SIC TECH® passes through. This allows the hot zone to radiate properly and helps maintain a uniform temperature in the kiln.

SPECIFICATIONS

OPERATING TEMPERATURES

In an air or inert atmosphere of argon or helium the SER SIC TECH® can be operated at furnace temperatures up to 3000ºF (1650ºC). In reducing atmospheres, the maximum operating temperature is 2500ºF (1370ºC). See Recommended Maximum Watt Loading Graph, Figure 1.

There is a protective coating of silicon dioxide on the silicon carbide. Hydrogen reduces this coating and causes the SIC TECH® to deteriorate. Nitrogen atmosphere applications are limited to 2500ºF (1370ºC) and 20 to 30 watts per square inch (3.1 to 4.6 watts per square centimeter) maximum watt loading. Higher surface temperature will result in silicon nitride formation. A thermally insulative layer forms around the SIC TECH® resulting in very high surface temperatures which damage the SIC TECH®.

ENGINEERING INFORMATION

SUPERIOR PERFORMANCE

At 2.8 gms/cc, this high-density low-porosity element is able to survive severe environments. The high density prevents the internal lattice structure from being oxidized. This element therefore has an extremely slow aging characteristic.

INTERCHANGEABILITY

SIC TECH® are premier grade high performance silicon carbide elements, and the only silicon carbide heating elements manufactured in Jiangsu Province, China. SIC TECH® can also be manufactured in special sizes and resistance values to replace elements supplied by other manufacturers in the US and Europe. It is important to provide the nominal electrical resistance when ordering SIC TECH®. Please contact us, before attempting to substitute the TYPE I SIC TECH® for spiral type SE/SER SIC TECH®.

ALUMINUM BRAID INFORMATION

• The working length of the SER and TSR aluminum braid is 10 inch (254 mm).

• The end clip hole diameter for 50 amp braid is 9/32 inch (7 mm), for 100 amp braid and higher is 9/16 inch (14 mm).

• The amperage rating of the aluminum braid according to diameter is 1/2 inch (13 mm) to 1 inch (25 mm) diameter – 50 amps, 1-1/4 inch (32 mm) to 2-1/8 inch (54 mm) diameter – 100 amps, 2-3/4 inch (70 mm) diameter – 400 amps, TSR elements – 1-3/4 inch (44 mm) to 2-1/2 inch (62 mm)

EASE OF REPLACEMENT

SER SIC TECH® can be replaced while the furnace is at operating temperature. The power to the SIC TECH® being changed should be shut off, the aluminum braids disconnected from the buss, and the old SIC TECH® removed. The new SIC TECH® should be inserted smoothly through the hot furnace but not so fast as to cause thermal shock.

SERVICE LIFE

SIC TECH® increase gradually in resistance with use. This characteristic of increasing in resistance is called aging. Aging is a function of the following:

1. Operating temperature

2. Electrical loading – usually expressed in watts per square inch or watts per square centimeter of SIC TECH® radiating surface

3. Atmosphere

4. Type of operation (continuous or intermittent)

5. Operating and maintenance techniques

SPECIFICATIONS AND MATCHING

SIC TECH® have a manufactured tolerance of plus or minus 20% on the nominal resistance. All SIC TECH® are calibrated at least twice prior to shipping to ensure their being within specifications. The calibrated amperage of each SIC TECH® is marked on the carton and collar of each SIC TECH®. When installing, arrange SIC TECH® with amperage values as close to each other as available. Longer service life will be obtained when series connected SIC TECH® are matched in resistance. SIC TECH® are shipped as closely matched as possible.