 |
HOME | SERVICES | SAFETY | LINKS | COMPANY | CONTACT |
| PACKED TOWER ANALYSIS ORIENTATION | |
|
Gamma scans yield valuable information for packed
towers. In order for a packed bed to function as
designed, the countercurrent liquid and vapor flows must
maintain as homogeneous a mixture as possible. A grid
scan is one method of quickly verifying and quantifying
the liquid/vapor distribution quality through a packed
bed. A Grid-Scan is comprised of four individual scans
in a grid pattern across four equal quadrants. A typical
Grid-Scan source and detector placement diagram is shown to the right. |
 click image to enlarge |
| NORMAL OPERATION | MALDISTRIBUTION | |||
| Good liquid/vapor
distribution in the packed section will generate a
uniform density pattern in which all four scan lines
overlay with each other. The amount of shared or
overlapping area of the scan lines provides a relative
measure of the quality of liquid/vapor distribution in
the beds. |
 click image to enlarge |
Maldistribution
can occur due to fouling material, poor initial liquid
and/or vapor distribution, or inadequate design, to name
a few. Maldistribution will reveal itself in a Grid-Scan
as varying densities of the four scan lines within the
packed bed elevations. Any spread among the four scan lines is a sign of maldistribution with a liquid bias being associated with lower radiation intensity (left side of the data plots) and vapor bias associated with higher radiation intensity (right sideof the data plots). |
 click image to enlarge |
|
| MISSING/DAMAGED PACKING | FOULING | |||
| Gamma Scans on
packed columns can reveal whether packing material has
been damaged or dislodged. This information will allow
the plant to have on-hand the proper amount of
replacement packing and eliminate expedite costs or
warehouse storage space for excess. In some cases, a
single scan may be sufficient to evaluate missing
packing. |
 click image to enlarge |
By design, packed
beds provide a greater surface area for liquid/vapor
contact in relation to trays, which is particularly
beneficial in vacuum services. One disadvantage of this
greater surface area, however, is the susceptibility of fouling material to accumulate if certain conditions are favorable. Grid-Scans will identify the presence of fouling in packing. The fouling typically reveals itself as a flooded section of the packed bed. The example to the right shows flooding in the upper section of a packed bed due to fouled packing. |
 click image to enlarge |
| TURNAROUND PLANNING |
| By having a more realistic and comprehensive insight
of the hardware replacement needs in critical path
vessels, we can help you to better define the scope of
your turnaround. The practice of gamma scanning towers
early in the turnaround planning stage has gained much
acceptance in recent years. This pre-turnaround scan
data not only provides the information to help define
the labor and material needs, but can also identify
areas where the plant can improve performance in the
months leading up to the shutdown. |
|
These are just a few examples of issues that gamma scans will identify in packed towers. Contact us to discuss the many other capabilities of packed tower gamma scans. |
