Plant engineers face nearly continuous issues with their trayed and packed towers to one degree or another. The impact on the operation determines the priority of getting this problem solved. The problem severity may be measured in throughput, lowered product specification, manpower or time; but ultimately the impact will be measured in dollars.
If an issue in your tower creates off-spec product or reduced capacity, the result is lower revenue. Depending on the affected unit, plant size, the product and the severity of the problem the lost revenue may be quite significant each day or it may be a slow trickle of revenue that adds up over time.
The Hidden Costs
Often overlooked are the costs associated with troubleshooting these process issues. Engineers, support staff and operations personnel are real expenses often dedicated to many consecutive days, or more often, intermittently over weeks or months, to working on identifying the cause of the issue and a solution. Investigations may involve engineering departments and specialists outside of the plant with a chargeback to your unit. The root cause of the issue may be elusive with extended troubleshooting needed to adjust operating parameters which can then upset the throughput or product specification even more. The effect may also span across multiple units or other plants that rely on your products.
The Direct Costs
If an issue cannot be resolved through the tweaking of the operating parameters, generally the tower is shut down for visual inspection or cleaning based on the current working theory. Shutdowns come at a high cost. Expenses directly related to the shutdown and lost revenue are easy to quantify and can be significant:
- Production is halted, resulting in lost revenue
- Operations personnel go through the shutdown routine: towers are cleaned, purged and blinded
- The maintenance crews are mobilized, this may include personnel, cranes and scaffold
- Spare internal parts such as trays, packing, distributors and demisters may be ordered
Through all of this, the increased safety risks associated with the work needs to be factored into the calculation as well as the direct cost of safety personnel and equipment over the shutdown period. There are also human resources, accounting and management expenses for the project.
The total dollar cost of a shutdown can be significant. The results of the shutdown may even have impacts on the personnel that made the decision to shut down as well as the planners. A successful plan may enhance a career while an incorrect or inconclusive result may slow your progress. One of the worst outcomes is to shut down and find no issues with the tower only to start up again and have the same issue or an even more severe problem.
The forgotten Tool: Gamma Scanning
A technique that is often overlooked in the troubleshooting and verification of tower problems is Gamma Scanning. The Gamma Scan is a tool. It provides information to the plant personnel on the operational characteristics and internal component status of towers. Gamma Scans are a non-invasive service and are performed while the tower is operating with often no disruption to the process or your capacity.
The Gamma Scan technique may be used on both trayed and packed towers and can be employed at any stage in the diagnostic procedure. The Gamma Scan may be used early to identify problems such as flooding, foaming, entrainment, tray loading levels, damaged trays, distributors and demisters as well as mal-distribution through packed beds. Gamma Scanning may be used in conjunction with operational changes to identify differences inside the tower that are not available through any other methods. Sometimes the results are obvious, other times they are subtle.
Gamma Scanning can be used to verify a theory and provide you confidence before making your decisions. Not only are Gamma Scans used for troubleshooting and debottlenecking vessels, but they are used extensively for shutdown planning of vessel entries. If a shut down is required, adequate planning can be done knowing the origin and extent of the problem as well as any hardware that may be required in advance of the shutdown.
Sometimes the result of a scan may disprove the current theory so that personnel can then concentrate on finding the true source of the problem. All information is useful information.
Use ALL of the tools at your disposal. Gamma Scanning costs are relatively low when compared to the other costs associated with tower problems and an ongoing diagnostic process. Seek out advice from the experts as it usually comes free of charge.