the rigging needed to allow for slight variations without creating instability in the load.
In addition, because the tridents and the main Cross T section were all made of specialty prestressed concrete, the rigging would have to avoid overloading the pipe wall and connected joints.
To meet those exacting requirements, Dearborn designed the rigging system around a rectangular modular spreader frame( CMOD) that could be resized to accommodate each component’ s dimensions.
The frame’ s nominal size was 11 feet by 11 feet, but on this job, it was used as large as 13 feet by 13 feet and as small as 11 feet by 11 feet.
“ Using the CMOD to lift the tridents and Cross T center box enabled balanced four-point vertical connection to the load, which minimized any chance of lateral stress,” said Walsh.
Each of the CMOD’ s four corners was connected to the crane’ s hook by a 15-foot synthetic round sling and to the load below by a wireless load cell and a 30-foot synthetic roundsling configured in a basket hitch.
“ We selected synthetic round slings and basket-hitch configuration to provide a relatively soft point of contact with the pipe wall,” Walsh said.“ And we deployed the load cells to verify and monitor load balance and the force applied to the pipe.”
He added that the load monitors were placed between the CMOD and the slings supporting the load in order to measure the forces most accurately.
“ As a matter of good engineering and rigging practice, it’ s best to place the load cell as close to the force point as possible,” he said.“ In this case, it was particularly important that we closely monitor all four points of connection as accurately as possible.”
The rigging also included four come-alongs to permit fine tuning of the load balance, as the actual center of gravity was not precisely known, and was different for each component.
Walsh said that the sling lengths were chosen to provide calculated sling angles and
December 2025 • www. thepartsconnection. org • 13