How should I evaluate whether to repair or replace my storage vessel?

September 20, 2018

As appeared in November 2017 PBE; Copyright CSC Publishing

Often the decision to either repair or replace comes down to dollars. Having a professional evaluation is a good starting point. Note that while this answer primarily addresses shop-welded vessels, the following points could apply to many different storage options.
Visually evaluate the vessel’s condition, asking the following questions: Are there signs of corrosion in the support skirt or columns? Is the coating (if there is one) in good condition? Are there any dents or deformations from flow problems, venting issues, or accidents? Has the material being stored changed in type or bulk density? Have modifications been made to the vessel that weren’t approved by the design engineer or manufacturer? Is the current capacity adequate, or is more required? Is the foundation sturdy? Is the anchoring system intact? Is everything still plumb and level? Also consider the site conditions: Is the vessel accessible? Can it be worked on safely?

The vessel’s age will help determine whether the design conforms to current building and construction codes. Many older vessels in good physical condition aren’t going to meet today’s standards because of code changes or changes to industry best practices. Ultrasonic thickness testing is helpful if you suspect the vessel shell has been thinned by corrosion or abrasion. This will also confirm whether the thickness of your shell material is adequate for your application.

Once you have a list of items to address, you can use that to obtain an estimate for repairs and can then compare that estimate to the cost of a new vessel. Sometimes, you have few options. For example, if your vessel is in the middle of a building with floors all the way around and no good way to remove and replace it, repair may be your only option. If your vessel has stored dangerous materials and the repair process could create an unsafe working environment, replacement may be your only option. If onsite repairs aren’t permitted or are cost-prohibitive, a structurally sound vessel could possibly be sent back to the manufacturer for refurbishing.

In any case, getting a professional opinion sooner rather than later is critical. A new vessel — or even a thorough refurbishing of an existing vessel — is an investment, but it can improve your operation and is less costly than the downtime and restoration associated with a vessel failure.

Mandy Landwehr, QC/QA manager, Imperial Industries, 715-359-0200