You just received a custom equipment design from Jenike & Johanson, to solve all of your handling problems. Now you need to have the equipment fabricated, so you send out for competitive bids. To your surprise, the quotes span a very large range. You suspect the high bidder of gouging you. Was the low bidder looking at the same set of drawings? Which one do you select?

Often, the difference between successful operation and failure of bulk solids handling equipment depends upon careful attention to details during fabrication. When evaluating any equipment bid, you should consider how well each bidder understands the requirements of the job. Not knowing the design intent and requirements for providing reliable material flow typically results in an underbid for the equipment. Sometimes the result is an extremely high bid.

One of our clients was expanding storage and handling capabilities for purified terephthalic acid (PTA). As part of the expansion, an existing silo would be retrofitted with a new mass flow transition hopper. The basis for the design of the new hopper was a similar hopper, designed and supplied by Jenike & Johanson, that was handling the same material. This hopper has been performing as intended since it was installed more than 20 years ago.

The hopper design was sent out for bids. Since its top diameter was only 10 ft., the unit could be shop fabricated, but access to the site in the plant was severely limited. Several pieces of existing equipment would have to be temporarily removed so that the new hopper could be installed. The estimated cost for relocating this equipment was significantly more than the cost of the hopper itself.

Since it was intended that the new hopper handle the material at a higher discharge rate than the old hopper, our client contacted us again, for assurance that the equipment would work as intended. Due to the high installation cost, a trial-and-error approach was not an alternative.

Our first step was to arrange a site visit for one of our senior engineers, Brian H. Pittenger, to see the existing equipment and to discuss the client's handling requirements. To ensure that the higher discharge rate could be achieved, we recommended small but critical changes to the previous design. These recommendations were based on recent flow properties tests, performed to ensure that the material's handling characteristics had not significantly changed over the last 20 years since it was first tested.

We then designed the transition hopper in sections that could be bolted together. This allowed installation with minimal equipment relocation costs while still ensuring reliable flow. Although the redesigned hopper was more expensive, the total installed cost was reduced by about 50%, since less equipment had to be temporarily removed for the installation.

To ensure that the project was handled correctly from beginning to end, we were awarded the contract for the detailed design and fabrication of the hopper sections. Timing was tight, but we delivered the equipment on time (approximately 8 weeks after the initial site visit), by working on the design details and fabrication simultaneously.

The new hopper has been in operation for several years. Our client describes it as one of the most reliable parts of the operation.

On any project, close communication between design engineer and fabricator is extremely important. The fabricator must understand the engineer's design intent, and the engineer must understand the fabricator's capabilities. Jenike & Johanson engineers understand what it takes to achieve reliable flow, from both design and fabrication viewpoints, and in a cost effective manner.