In the world of industrial safety, the integrity and reliability of vessels, particularly those used in high pressure environments or situations where explosions could occur, are extremely important. This article explores the critical process of evaluating the safety and suitability of these vessels. From visual inspections to advanced techniques like ultrasonic thickness testing, we discuss how professionals make informed decisions regarding the maintenance, repair, or replacement of industrial vessels to ensure safety, compliance, and cost-effectiveness.
Visual Inspection vs. Ultrasonic Thickness Testing
JBW Consulting Engineers once worked with a client in the ethanol industry. We conducted a safety assessment at their facility, focusing on the area where dry materials are processed, and found a dust collector with vents positioned near other equipment. We also noted that the vents were smaller than current standards recommend.
When we discussed these issues with the client, they were willing to fix them. We contacted the manufacturer of the equipment for advice on a new vent, but they gave a vague reply. They couldn’t confirm if their Pred value was still accurate without knowing the current state of the dust collector. Manufacturers typically respond this way because they have no way of knowing how much wear and tear the vessel has endured or if it has been exposed to harsh conditions.
We believed there was another solution besides replacing the dust collector. Visually, the equipment looked fairly new and well-kept. If it wasn’t too worn or damaged, and we had some data to support the visual assessment, it might be reasonable to either keep using the original Pred value or adjust it based on what we found.
Our on-staff API 510 certified vessel inspector performed a vessel inspection. Along with a detailed visual inspection, an ultrasonic thickness meter was used to examine various vertical lines on the vessel’s exterior, paying special attention to high erosion areas like the inlet and outlet. The assessment revealed a few dents but overall, the vessel was in good shape, so we determined it was safe to continue using the original Pred value. We then helped specify and install new vents in better locations.
The key point here is that most facility managers really want to do things right. Being told that their reliable dust collector needs to be replaced can be difficult to accept. Upgrades, like fitting larger explosion vents or moving them, are more cost-effective than replacing the entire vessel. The method described here people an easier way to meet safety standards.
Can This Process Establish a Reduced Value for Your Vessel?
The NFPA standards suggest using 0.2 bar as a default value if there aren’t more specific details. Whether this assumption is universally suitable remains debatable. However, merely knowing the vessel’s condition doesn’t necessarily provide the Pred value. Instead, it indicates if the original Pred value attributed to the vessel remains a safe choice.
If we find problems, like thinning or visible damage, we have to make a decision. For example, we might conclude that the reduced strength of the vessel is uncertain and that it’s unsafe to assume the original Pred value is applicable. Alternatively, if the vessel’s defects are localized, we might consider designing a solution to address these shortcomings. This could mean adding extra material or vessel replacing material to make sure it can handle the necessary pressure. Such repairs would require detailed analysis and calculations, but can still be cost effective.
Visual Inspection vs. Ultrasonic Thickness Testing
Any API (American Petroleum Institute) certified inspector would recommend doing both types of checks to really understand the vessels condition. Given the limited thickness, we aren’t searching for impurities in the metallurgy. What we do is a vessel inspection that checks for dents, damage to important components, misalignments, missing or damaged bolts, and other issues. It’s important to be thorough: even if a few ultrasonic tests show that the high-wear areas are fine, there could still be other problems with the vessel.
Even if the thickness measurements look good, visible corrosion in key areas can be a serious issue. The trick lies in combining both evaluation methods – leveraging one’s experience with these vessels while also employing ultrasonic thickness testing to pinpoint wear.
How Can You Avoid the Need to Replace the Vessel?
If thinning occurs in a certain area, we could remove that part and replace it. It’s important that the new welds can handle the original pressure. We could also make the vessel thicker in those areas, especially if erosion will continue to be of concern.
For mechanical damage, the approach might be similar. For example, if there’s damage on the cone part of a cyclone, we could attach a curved plate over it, essentially replacing the damaged area. We would need to prove mathematically that we’ve restored the vessel to the original strength. As for corrosion, the approach is the same, but corrosion can be trickier, leading to more complex issues.
We have performed finite element analysis on pressure containing vessels at times when custom modifications and shapes are necessary. It could also be done to determine a Pred value of a vessel. Many manufacturers use this method to set an original Pred value.
Conclusion
Ensuring the safety and effectiveness of industrial vessels, particularly those used in high-pressure or potentially explosive situations, requires careful evaluation and decision- making. Conducting thorough inspections, both visually and through methods like ultrasonic thickness testing, is crucial to accurately assess the condition of a vessel.
Decisions on whether to repair, reinforce, or replace a vessel depend on these detailed evaluations. Using a combination of professional experience, standard practices, and advanced analysis like finite element analysis helps in making informed decisions that ensure safety and compliance while also considering cost-effectiveness and practicality. This approach not only enhances the safety and longevity of the equipment but also provides a more sustainable and economical solution for industries relying on these critical vessels.
