Raschig Rings

One standard type of glass column packing is available: Raschig rings. It is especially suitable for use in glass columns because of its low bulk density. 

Selection and use of column packing 
1. The ratio of column diameter to packing diameter should not be less than 8:1. 

2. Where smaller sizes of packing are used, it is sometimes advisable to use a small layer of larger packing immediately above the support to prevent the smaller packing falling through. 

3. In vacuum operations and applications involving high vapor velocities glass packing--because of its low weight--may tend to be lifted away from the top of the column sections and may cause damage to other parts of the installation. This can be prevented by fitting a suitable form of restraint (for example a perforated plate) above the column section. 

4. Various methods can be used for the random distribution of packing in a column. One method is to fill the column section with water, then dump in the packing. If this is used, care must be taken not to exceed the maximum pressure permissible in the column. 

5. Column packings other than the standard glass ones can be used but bulk density should be taken into consideration and the maximum permissible load on the support should not be exceeded.