CPA Installs Fall Protection at Aerospace Facility

Casper, Phillips & Associates Inc. (CPA) has designed and installed a bespoke fall protection system for a large commercial airplane supplier.

CPA was contracted to integrate it with 67 separate bridge cranes that vary in capacity from 34 tons to 40 tons and cover three million square feet. The galvanized chain-link (ASTM A392-07) installation allows crane operators and maintenance personnel to transition from a 90-foot-high catwalk to crane bridge egress platforms without wearing personal protective equipment (PPE), which involved the time-consuming process of attaching and disconnecting harnesses.

The crane bridge spans vary between 100 feet and 150 feet. Lift heights are all approximately 67 feet. A low-weight solution was needed to not structurally impact the bridge and rail system. The CPA net frames offer the added benefit of allowing workers to see through them. The system was tested by dropping a 400-pound sandbag from a height of 55 inches.

“The project was unique because of the time constraints required to install the frame and no two bridges were alike. They all appear alike at first sight, but the location and orientation of limit switches always changed,” said Andrew Hanek, a civil engineer, CPA. “As-built conditions of things like the ladder and ladder cage changed or had angles mounted backwards. Space limitations were also a huge concern since the bridges still had to go bumper-to-bumper for picks and we had minimal clearance vertically with the roof truss system.”

Many of these differences were either inadequately documented or not documented at all. CPA decided that the best path forward was to leverage handheld 3D scanning technology and scan all the cranes for these minor differences. CPA created a primary design that could be slightly modified to fit each crane without any costly interferences.

The bridges were scanned from the bridge and factory catwalks, a maintenance trolley for areas between the bridge girders, and the top of the egress platforms. The top of the platforms did not have a lot of unique features so stitching the point clouds across the platform did not give good results. CPA decided to reference the point clouds to the bridge girder and assume that the 12-feet on center spacing was precise. This method, combined with photos, allowed CPA to identify all features of concern to work around.

“The installation crew eventually got it down to the entire process for a single bridge being performed in a 12-hour window. Net frames were fabricated and staged ahead of time so they could be hoisted into place and installed. If needed, relocation of electrical conduit and junction boxes was performed prior to the frame installation. The short install time was a huge success since production was not able to lose bridges for days at a time,” added Hanek.

The relevant safety code for the galvanized chain-link installation is Chapter 296 155 WAC Construction Work.

For more information, visit http://www.casperphillips.com.