Be careful when getting bids

When getting bids, don't invite trouble, as well as proposals.

By Mark Rosenzweig

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The operating rate at Copius Chemicals’ Ft. Decatur plant had been climbing steadily since early 2004. It now stood at 78% and the gurus at corporate headquarters outside of Chicago forecasted a continuing increase in demand for the next two years. Ed Santiago, an engineer at the plant, worried that a 30-year-old distillation column filled with valve trays might prove a bottleneck in reaching nameplate capacity, much less exceeding it. An applications engineer from the vendor that had supplied the original internals looked at the column and seconded Ed’s opinion. His recommendation was to retrofit the tower with higher-capacity proprietary trays.

Copius had cut back capital spending significantly during the slowdown a few years ago, and still was cautious about making investments. However, Ed effectively made the case that revamping the column was essential and management quickly gave him the go-ahead. While that was good, it also meant that this was going to be a high-profile project.

Ed knew that developing a request for a quote demanded more expertise than he had about distillation. And, he wondered how well he would be able to compare the various proposals that would come in, especially since they might differ in some significant respects.

Unfortunately, Copius had disbanded its central engineering group more than a decade ago, deploying some people to plant sites and retiring many veterans. No column had been built or retrofitted at Ft. Decatur in decades, and no one on site had any real in-depth knowledge of distillation; Ed couldn’t find a single distillation specialist elsewhere in the corporation, either.

He realized that he needed help; he didn’t realize, however, how many factors really come into play for a sophisticated piece of hardware like a distillation column.

As John Kunesh and Ray Sowiak point out in their article on p. 30, many traps lurk for the unwary. Determining design loadings can be tricky and should not be based solely on the results of a simulation. Potential bottlenecks from auxiliaries like the condenser and reboiler must be considered. Likewise, it pays to check the system limit of the column shell. And the list goes on.

Also, it is essential to take steps to ensure that the quotes are on a comparable basis. The commonly used term percent of flood (or percent of maximum capacity) means different things to different vendors, warn Kunesh and Sowiak, and can complicate comparisons unless this issue is addressed upfront. Likewise, while it makes sense to take advantage of the experience and know-how of suppliers, it is important to accept alternatives to the base bid, not in it.

Luckily, Ed had the sense and the budget to bring in an expert and the project hopefully will wind up a high-profile success. However, too many other engineers undoubtedly feel that they must deal with such situations on their own. And their well-meaning efforts might not turn out so well.

Some guidance from an experienced practitioner can make a big difference in such situations, or whenever an engineer faces unfamiliar technical territory. So,  Chemical Processing now has launched an “Ask the Experts” section on our Web site in which you can pose questions concerning 20 key technical topics, including distillation. It can help you turn good intentions into good results.
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