Over the years many shapes have been proposed for tower packing elements, but only a few are widely used. Probably the oldest random dumped tower packing shape in substantive commercial use is the raschig ring. This packing is a simple cylinder with a length equal to its outside diameter. It is manufactured from ceramics, metals, plastics, and carbon. Two modifications of this shape are the Lessing ring and the cross-partition ring. Both of these shapes use internal partitions. These packings have been installed in both a dumped and a stacked manner.
A further modification of the basic cylindrical shape involves installation of a helix inside the cylinder. The interior of this ring may contain a single, a double, or a triple helix. This spiral ring packing normally is made from ceramic and only should be installed by stacking.
The first of the modern dumped packing was the berl saddle, developed in the late 1930s. This shape has a significantly increased surface area per unit of packed volume compared to the raschig ring. Another improved shape was the intalox saddle developed in the early 1950s. This design has two different radii of curvature that provide a greater degree of randomness in the packed bed.
In the early 1950s a significant improvement was made in the raschig ring shape by BASF. Their development, called the Pall ring, consist of a cylinder of equal length and diameter with ten fingers punched from the cylinder wall that extend into the packing element interior. Although the Pall ring has the
same geometric surface area as the Raschig ring, the interior surfaces of the Pall ring are much more accessible to gas and liquid flows due to the
openings through the wall. Subsequent Pall ring configurations, such as Hy-Pak packing that have further increased the percentage of internal surface area the packing element makes available for gas and liquid contact.
A further modification of the Pall ring was developed by Mass Transfer Limited. Their Cascade Mini-Ring also is a cylinder with fingers punched from the wall projecting into the interior of the ring; however, the height of the cylinder is only one-third the outside diameter. This shape is told to orient itself preferentially when dumped into a packed bed.
A newer packing element combines advantages of the shape of the intalox saddle with that of a modern ring packing. This intalox metal tower packing, or IMTP packing (trademarks Norton Chemical Process Products), was developed by Norton Company in the late 1970s and is manufactured from metals only.
A filamentous packing shape was developed by Dr. AJ Teller in the 1950s. This Tellerette is produced only in plastic. To satisfy the demand for a very low pressure drop packing for use in pollution control applications, developed Intalox Snowflake packing. This plastic packing has been available since 1987. This unique shape provides the maximum number of uniformly shaped, interstitial liquid drip-points. This feature causes continuous renewal of the liquid surface, which greatly enhances its mass transfer efficiency. This packing has found use in humidification, dehumidification, absorbers, scrubbers, and strippers etc.
As still in development, that's the outline history of the random packing history, it just include the main kind of dumped tower fillings.