Before choosing the random packing, factors and characteristics of packing need to be checked and verified as,
• It should meet the process requirement.
• Need to check whether the direct replacement of an already existing packing is suitable with the process or not.
• Selection of the process familiar packing and its performance in the process.
• Experience with a certain packing with a specific application.
• Can it be used in a licensed process or not.

These are some factors need to be properly verified before selecting a random packing. More the specifically characteristics checked, better will be your selection for your process. Each and every factor like measurement, voids, wetting rate, surface area, efficiency, and density should be more specific which decides the overall performance of the selected packing.

There are some specific characteristics are listed below which must be checked for your process application.

1.The Surface Area

Efficiency of the packing is depending on surface area. Higher the surface area more will be the efficiency with respect to increased vapour contact. Therefore, the efficiency increases with lower packing size.

2.Uniform spreading surface
The vapour-liquid contact enhances the efficiency where the vapour-liquid contact can be enhanced by the uniform spreading surface. Pall ring and Raschig rings of equal size has similar surface area, but latter has a better spread surface as compared to the former, and hence latter is more efficient.

3. An uniform distribution
Random packing rings that can be fixed together with their counterpart can lower the efficiency when they form channels. Packing should also drain fluids freely to prevent liquid settling pockets as it was common with the older saddle type of packing. So the uniform distribution of the fluids also matters to maintain the performance.

4.The rate wetting

Minimum stability means the lower wetting rate. Dewetting of the packing surface occurs when the liquid on the surface of packing is interrupted or disturbed by falling liquid. When packing surface Dewets it causes a decrease in efficiency.

5.Voids in the packing
High voids means lower the pressure drop in vapour flow and higher will be the capacity as there is more space is available for vapours. Capacity increases with the particle size of the packing. The suitable size of packing should be selected with well-balance between efficiency and capacity.

6.The material used in random packing
Metal packing’s are unbreakable, offer higher capacity, turndown and efficiency comes in different shapes and they have a higher resistance to compression.

Ceramic packing’s work best in applications where high chemical inactivity, corrosive applications and high-temperature resistance are required. They offer low capacity, are breakable and are available only with specific shapes and not in popular geometries.

The most affordable packing’s are those made of plastics material mainly of polypropylene, but they can’t withstand higher temperature as above 1220C (2500F) depending on the grade. They can be degrade in applications of such oxidizing environment and solvents. That’s why they are kind of unsuitable for such applications. They have poor wet ability hence lower efficiency.

7. Friction
Capacity is higher in random packing when friction is minimized by using open shape which has aerodynamic characteristics.
8. Strength
Packing must have strength to bear load which is applied on it in the working conditions. It should resist mechanical damage so that it can last longer.