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Technical Advantages

• Superior mechanical at all precipitator operating temperatures - about four times stronger than electrical porcelain
• Excellent electrical resistance properties at all temperatures
• Outstanding chemical and abrasion resistance from acids and chemically reactive particulates - harder than all metals and most man-made material

What is the difference between 85% Alumina Ceramic vs. Electrical Porcelain?

The insulator industry generally refers to porcelain ceramic insulators as "electrical porcelain", but, occasionally, the terms "alumina-porcelain" and "alumina-based porcelain" have been used. These products contain 35-48% by weight aluminium oxide and have specific gravities of 2.4 to 2.7.  85% alumina is sometimes called "high alumina".  The Specific gravity will typically be 3.40-3.45 (see table below). 

To be considered as alumina ceramic, the product must contain at least 80% by weight aluminium oxide. At approximately 80%, a radical change occurs in the crystal structure of the ceramic. Above this level, the aluminium oxide becomes a stable phase. A crystal structure examination reveals an alpha lumina phase in a glassy matrix.  Conversely, the porcelains will show some combination of mullite, quartz, glass, and possibly feldspar.  The alumina that?s present in porcelains is absorbed into the mullite or glass phase.

It is the alpha alumina phase that imparts superior properties to 85% alumina ceramic. For example, tensile strength will be 140-170 Mpa (20-25 kpsi) for 85% alumina versus around 34-35 Mpa (5-8 kpsi) for porcelain.

Glazed or Unglazed?

Although our 85% alumina insulators are available either glazed or unglazed. Unglazed is recommended for all precipitator applications. This is because 85% alumina insulators are extremely dense and will not absorb liquids or gases. Therefore, a glaze coating is not required to seal the body of the insulator.

An unglazed 85% alumina insulators provide better service than glazed insulators because:

• They are more resistant to attack by aggressive particulates and gases.
• Unglazed surfaces will not soften at elevated temperatures - soft glaze will become sticky and dirty from tightly adhered particulates.
• It is superior to glazed for electrical resistance, especially at elevated temperatures.