Devil in the Details: Measuring Complex Pressure Vessels

Once the alpha version was reached and consistency in measurement was established, it took as little as a half a day to train additional operators on how to use the new system with the alpha programming.

Originally though, the programming had one coordinate system alignment based on part features that was used only to measure the final product. Since that first program, CBW has integrated two more iterative alignments used to report large bolt patterns of 48 or more holes and their conformance to tolerance independent of other unit features.

The programming uses a portion of the measurements for one alignment, generates a report, uses a new set of features for another alignment, generates a report, and finally the last alignment with a third and final (overall) report.

From that original starting point and after advanced training, CBW added measured features to the final measurement program as well as a number of in-process measurements. The result was a robust quality system for their primary products using the FaroArm and CAM2 software.

More specifically, this system has grown from the one “seed” program of one measurement of one product size to over ten programs spanning three product sizes. Even the CAM2 software ability to output raw data has become an integral component of the quality system for these products with respect to third party data.

The primary parts mentioned here are so large and difficult to measure using analog methods that once confidence in the new inspection system was established, the technology was quickly accepted by everyone from welders and fabricators on up to the president of the company.

There are two core components of the final product that are measured after they are produced, but before they are used in unit fabrication. CBW also uses the FaroArm during assembly to ensure that the key connections are located within tolerance before they are locked into place.

Then, of course, there is a final measurement of the finished product. In general, there are four FaroArm measurements and reports that are analyzed during the construction of the two larger-sized primary products detailed earlier.

This range of products is an example of the unique work done by CBW and presented a unique measurement challenge for the inspection system. In other words, the designs of each size are property of CBW, but by the nature of their application they are developed in conjunction with the end customer. Products this large, having so many features, require several device moves.

Both the final product tolerances and those applied at the in-process inspection points are so tight that sometimes alternative alignments must be used to check for real-world conformance. Sometimes technicians must simply check to see if a particular unit will actually fit into the assembly.

To do this they have the programming perform iterative alignments over varying geometries ranging from single bolt hole patterns of 52 holes in a single plane to 2 bolt hole patterns of 12 holes each and 7 different connection points.

In addition, CBW has qualified several shop fixtures using FARO and is in the process of designing more elaborate fixturing for production that will also be qualified as accurate build tools using the new inspection system.

RETURN ON INVESTMENT
Over the last three years approximately 37 units have been built and measured using the new inspection system. In this time, the measurement procedure has increased in depth from just a final measurement of a finished unit to preliminary measurements and measurement of individual fabricated components before assembly even begins.

“We have been able to reduce the variance of in-process placement of key features from as much as 7/16 in to 1/8 in from one unit to the next,” said Marc Dinsmore, a mechanical design engineer at CBW. “This new system allows us to become so consistent and accurate from build to build that the largest cause of variance between builds becomes the actual mill tolerances on the raw material being used!”

There have also been several instances where the FARO system has proven to be a valuable tool for reverse engineering during exchanger rebuilds and boiler re-tube contracts.

These types of jobs require careful measuring of corroded or incomplete components with many mating surfaces. Accurate measurement is vital to the success of these jobs and the FARO system ensured near perfect replacement parts by virtue of its accuracy and its robust data collection.

Though these jobs were previously completed without the new system, they lacked the confidence and streamlined efficiency that system affords more difficult jobs.

The CAM2 software’s ability to preserve data for documentation and future analysis has also proven to be very valuable. Going back into previous builds has allowed the shop to see the improvement in their processes and will prove more and more valuable as additional data is extracted.

Though it is difficult to always quantify a dollar amount on savings and, in this case, using the FARO system actually added some time to the build process, the company is more interested in the end result: the assurance of accurately placed features, which is the ultimate goal.

That assurance did not exist using analog methods. Without the new system, the inspection could not be completed in the desired detail and that should always be the goal of any quality process.

The overall savings in developing this FaroArm quality system came from eliminating much of the costly rework at the end of the build through in-process inspections. The results of some early inspections led to fabrication process changes that eliminated much of the weld distortion that was found.

“Having just scratched the surface of this system’s value,” said Dinsmore, “I can easily say that several key benefits we’ve experienced have been reduced work, shortened build times, improved build quality and consistency, improved insight to some of our standard procedures, and confidence in many replacement and/or repair contracts.”

“I must tell you,” he concluded, “that I have great faith in our Fusion and the customer service we have received in the past couple of years!” The confidence in the methods and technology took approximately nine months to develop, but once it was reached, the company now leans on the system more and more in daily operations.

Cannon Boiler Works, Inc., 510 Constitution Boulevard, New Kensington, PA 15068, 724-335-8541, [email protected], www.cannonboilerworks.com

FARO Technologies, 125 Technology Park Lake Mary, FL, 407-333-9911, www.faro.com.