Type I sic heating element

TYPE I ELEMENT

The TYPE I element is a resistance-type silicon carbide heating element. SIC TECH® elements are rod-shaped or tubular, depending on the diameter. They feature a central heating section known as the hot zone and two terminal sections referred to as cold ends.

There are two types of TYPE I elements:

• Cold ends impregnated with silicon metal — referred to as the one-piece type.

• Low resistance cold ends that are furnace-welded to the hot zone — referred to as the three-piece or LRE (Low Resistance End) type.

This lower electrical resistance cold end design allows them to operate at a reduced temperature. The extremities of the elements are metallized with aluminum to provide a low-resistance contact surface, to which the electrical connections are made using braided aluminum straps.

MOUNTING

There are no restrictions on the mounting positions of SIC TECH® elements, although horizontal and vertical orientations are the most common. Extreme caution should be exercised during installation to ensure that the SIC TECH® elements are not placed under tension. Adequate freedom must be provided to allow both the furnace and the SIC TECH® elements to expand and contract independently.

When mounting SIC TECH® elements vertically, they must be supported at the lower end by electrically insulated supports or suspended from above using support pins on an isolating plate that is strong enough to bear the weight of the elements.

The ends of the SIC TECH® elements should extend beyond the furnace cold face by a minimum of 3 to 4 inches or 3 times the element diameter (whichever is greater). When using sealed terminal boxes, the cold ends should extend by a minimum of 4 to 5 times the element diameter.

SIC TECH® elements should have their heating sections centered within the furnace chamber, ensuring that no part of the heating section extends into the furnace wall. To promote proper radiation and help maintain uniform kiln temperatures, a conical or truncated cone-shaped recess approximately 1/2 inch (13 mm) deep is sometimes positioned on each interior wall where the SIC TECH® element passes through.

SPECIFICATIONS

OPERATING TEMPERATURES

In clean, dry air, one-piece SIC TECH® elements can be operated at furnace control temperatures up to 2912°F (1600°C), while three-piece SIC TECH® elements can operate up to 2600°F (1425°C). In inert atmospheres such as argon or helium, one-piece elements may be used at temperatures up to 3092°F (1700°C).

For atmospheres containing water vapor, alkali metal species, flux vapors, or oxygen enrichment, we recommend our LMA infusion glaze-coated TYPE I elements or elements of type TYPE I-HD, TYPE SPIRAL SINGLE, or TYPE SPIRAL DOUBLE.

In reducing atmospheres, the maximum operating temperature is 2500°F (1370°C). A protective silicon dioxide coating naturally forms on the silicon carbide surface. However, hydrogen reduces this coating, which leads to SIC TECH® element deterioration. Both very dry and very wet hydrogen are detrimental to long service life.

Applications in nitrogen atmospheres are limited to 2500°F (1370°C) with a maximum surface watt loading of 30 watts per square inch (5 watts per square centimeter). Excessively high surface temperatures can result in a silicon nitride reaction, forming a thermally insulating layer around the SIC TECH® element. This causes extreme surface temperatures that can damage the elements.

ENGINEERING INFORMATION

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 SIC TECH®.

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 Starbar radiating surface)

3. Atmosphere

4. Type of operation (continuous or intermittent)

5. Operating and maintenance techniques

SPECIFICATIONS & 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 right hand end 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.