The RR Starbar is a resistance type silicon carbide heating element. Starbars are rod shaped or tubular depending on the diameter. They have a central heating section referred to as a hot zone and two terminal sections called cold ends. There are two types of RR Starbars. (1) The cold ends are impregnated with silicon metal - referred to as one piece, and (2) low resistance cold ends which are furnace welded to the hot zone - referred to as a three piece or LRE (Low Resistance End) type. This lower electrical resistance cold end causes them to operate at a lower 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 ...
The right angle (RA) element is a heating element that has two cold ends, welded at right angles
to the opposite ends of the hot section. The maximum recommended furnace temperature is
1425ºC (2600ºF). The element is manufactured of high density recrystallized silicon carbide.
The two cold ends are low resistance silicon carbide. The diameters available range from 13 to
54mm and hot zone lengths up to 1500mm and cold ends up to 480mm long.
The RA element is ideal for launders where terminal connections are on the top of the furnace.
The RA element has support holes in the cold end so the element can be installed with the cold
ends through the roof. Cotter pins and washers are included with each element.
The Starbar TW element is a higher density element, used in severe applications such as corrosive atmospheres or where normal RR type elements do not provide acceptable service life. The TW element has a typical density 10 to 12% higher than normal RR elements. This higher density results in slower oxidation and aging, which yields longer element life. The dimensions and electrical properties of the TW element are similar to those of the RR element, therefore, a TW element may be interchanged directly for an RR element. The TW element due to its higher density may be more prone to thermal shock during installation into hot furnaces. Special care should be used not to thermal shock new elements during installation and heat up.
One of the earliest heating element designs, the enlarged cold ends of the Dumbbell style element were originally made oversized to increase cold end cross section, lowering electrical resistance, thereby lowering cold end operating temperature. Modern Dumbbell Starbars, by contrast, employ an advanced technology to keep the terminal ends cool by virtue of the decreased resistivity of the lower resistance cold end material used in the manufacturing process. Oversize cold ends are therefore no longer necessary. Non-dumbbell (RR Starbars) can be substituted for Dumbbell Starbars. Improvements in the cold-end-to-hot-zone resistance ratio between the original DB and new DB Starbar have been dramatic. The old style resistance ratio was 1:3, ...
Made of high density recrystallized silicon carbide, these multiple leg Starbars use the same hot zone and cold end material as the RR type Starbars and offer a configuration that allows the electrical connections to be made at one end. The low resistance terminal ends allow for cool operation. The LRE (low resistance ends) have a high (15:1) electrical resistance ratio to the hot zone section. The first several inches of the cold ends are metallized with aluminum to provide a low electrical resistance contact surface. The electrical connections are made using flat aluminum braids held in compression to the circumference by a stainless steel spring clamp. U type Starbars are described by giving the overall length, the heating section ...
Star performers in float glass production, TYPE W THREE PHASE Starbars® are comprised of high purity, high density, silicon carbide grains, self bonded through recrystallization at elevated temperatures. Sintering at temperatures in excess of 2200ºC provides a structural density of 2.50 grams per cubic centimeter. Such high structural density results in Starbars® of maximum strength and minimum porosity, with an extremely slow aging characteristic.
Strength of the Starbars® is further enhanced by insertion of hot zones into oversized cold ends. Enlarged cold ends measure 28 mm (1.10") in diameter, accommodating hot zones of 19 mm (0.75") in diameter.
The spiral Starbars are made of special high-density reaction-bonded silicon carbide. A spiral slot in the hot zone reduces the cross sectional area. This provides the electrical resistance ratio to make the ends cool and the hot zone hot. Special cold ends may be welded to further enhance the resistance ratio. To provide a low resistance contact surface the extremities are metallized with aluminum. The electrical connections are made with flat aluminum braids and spring clamps. The terminal ends of the SE element are normally plugged.
SE and TSE Starbars are described by giving the overall length, the heating section length, and the diameter. As an example, SE 36 x 14 x 1 is a spiral element 36" long with a 14" hot zone and 1" ...
Made of special high-density reaction-bonded silicon carbide, the SER Starbar 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 ...
Made of special high-density reaction-bonded silicon carbide, the SEU Starbar is a tube with both electrical connections on one end. The hot zone is formed by cutting a slot, which reduces the cross sectional area over which the 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 and is made of LRE (low resistance end) material and in most cases is larger in diameter.
The SEU element is supplied with a ceramic collar cemented to the cold end. The cold end of the SEU element is flame sprayed with aluminum for a distance of about two inches. Flat, braided-aluminum straps are held in compression with a stainless steel clamp to this ...
The element terminal holes in the furnace walls must be in line and be large enough in size to prevent the element or terminal tube from being pinched at all furnace temperatures. Terminal tubes are optional but recommended for use with the SER and TSR elements and with fiber wall furnaces. Some furnaces have a potential problem of electrical conduction to ground. The ceramic terminal tubes have superior electrical resistance properties and can prevent this from occurring.