What should be determined when coke deposits are found in a vessel?

When coke deposits are discovered in a pressure vessel, it is crucial to determine the thickness of the vessel material beneath those deposits. This is important for several reasons. Firstly, coke deposits can lead to localized corrosion, which may cause significant thinning of the vessel wall that might not be visible externally. Assessing the thickness helps ensure that the vessel maintains its structural integrity and is safe for continued operation.

Measuring the thickness under the deposit allows inspectors to identify whether the corrosion has compromised the vessel beyond acceptable limits. It also helps in planning any necessary repair or maintenance actions, as well as determining the remaining life of the vessel. If significant thinning is identified, it may be necessary to take further action, such as repairs or replacement.

While other aspects like chemical composition may also be relevant to understanding the nature and risks associated with the coke deposits, without assessing the thickness, one could overlook potentially critical safety issues within the vessel. Thus, determining the thickness under the deposit is a fundamental step in the inspection process when coke deposits are present.