You troubleshoot plants for a reason. The reason is that the plant isn’t doing what you want. For the plant engineer, the ideal solution resolves the problem with an operating change rather than an equipment change. Operating changes, once they have moved through the required reviews, typically cost less and happen faster. Nevertheless, many changes require equipment to be repaired, modified or replaced.

The simplest changes use repairs or replace-in-kind parts to bring the plant back to its normal operating capabilities. The plant has already been constructed and reviewed for the repaired configuration. All safety and regulatory reviews should have been completed for that operation, and getting back to it is straightforward. Now, straightforward does not necessarily mean easy or cheap, but the steps to be taken are usually clear.

Things can change rapidly when modifications cross a threshold. The threshold may include both technical and regulatory issues. These issues can bog down what appears to be the simplest modification. Let’s look at an example.

In the 1950s, many foundations, even in industrial facilities, used wood pilings. The wood might have been treated with chemicals that are no longer permitted in this service. To solve a new operating problem, one plant wanted to improve its operation, but the new equipment would add weight to the structure. In addition, even for the same loads, foundation requirements have increased dramatically over the decades. This is compounded by ambiguity in both the original and current requirements for foundations. What does no material change in loads mean? This was an important question without a clear answer. Even the local regulatory authority couldn’t come to a clear definition of what this meant.

Four major definition choices were proposed. First, the total weight on the structure had to be less than its original design weight. Second, the total weight on the structure had to be less than the weight it was originally placed under when it was put into service. Third, the weight on the structure had to be less than or equal to the current weight, which was less than the originally constructed weight due to the removal of equipment. Or fourth, the weight on the structure had to be less than 110% of its original design load. The answer was important because once the foundations had to be modified any changes were no longer practical. I’m not sure if this issue was ever resolved.

But how was the immediate problem resolved? The decision was made to use different construction materials, which reduced the equipment's weight. The design matched the weight of the replaced equipment to the pound. If the third option was the answer, the idea was that making the new equipment too light would just make the problem worse for any future changes.

The better solution would have been to resolve the understanding of the foundation limits. However, external factors prevented the plant turnaround date from being moved. To meet this date, decisions had to be made, and an overall execution schedule had to be met. It quickly became clear that resolving the foundation question wouldn’t fit the schedule. So, an assumption was made, and decisions went ahead.

The key thing here is that once the plant moves beyond simple repairs or replacements-in-kind, many problems can arise. These problems are not always apparent to the unit engineers involved. In this case, the foundation question was outside the competence of the typical unit engineer. The foundations became the key element, setting the practicality and schedule for the entire upgrade. These types of questions can arise in any technical or regulatory area for plant upgrades. It’s critical for the plants to involve as much experience as possible, as soon as possible, when considering plant changes. If not, surprise will lurk and catch you at the worst time.