March 2014, Vol. 241 No. 3
Features
Midwestern Contractors Case Study On Suspended Pipelines
Integrity projects are complicated enough when they involve locating anomalies along a buried pipeline that will then need to be excavated, evaluated and repaired. That factor increases significantly when the pipeline involved is connected to a heavily traveled motor bridge over a busy commercial river, adjacent to an active railroad spur in a large metropolis like Chicago – in the dead of winter.
A large liquid pipeline operator needed to replace corroded hangers that were supporting its pipeline on the bridge so the company turned to Midwestern Contractors and an Orbital Engineering for a solution.
The liquids pipeline is suspended over the Grand Calumet River on the 130th Street Bridge. This 366-foot span of 12-inch pipeline was being held in place by 19 hangers. The hangers were weakened by corrosion from water and road salt. Further complicating matters, the city of Chicago needed to do work on the bridge bearings which required jacking the bridge up as much as a half inch.
The solution to such a situation involved detailed planning and clear communications between contractors, engineers, pipeline owners and regulators. To ensure safety and success, and to protect the pipeline and bridge assets, all of the issues involving, fabrication, welding, painting, bolt and torque specifications, lift plans and job site analysis, were worked out in advance.
While the engineering firm worked on the design and drawings for the hangers, Midwestern Contractors was charged with developing the construction plan, securing a lease for access and laydown area, and writing and securing permits from the Corps of Engineers, Illinois Department of Natural Resources and the Coast Guard. After almost two years of work, the necessary permits were secured, the hangers were designed and fabricated, and the construction plan and subcontractors were in place for a January 2012 kickoff.
The logistics proved to be challenging. The main span had to be accessed by barge and the approaches to the east and west required scaffolding. On the west side the scaffolding had to bridge a rail spur to prevent interruptions in service to a pig iron yard. Scaffolding was required on the east side, too, but land access proved infeasible so the west side was also used as a staging area for the portion to be barged across the river and off-loaded for assembly on the east side.
Midwestern crews started the project on a bitterly cold Jan. 15 at some nearby docks where a work barge was loaded with equipment, including a 90-ton crane, an aerial man lift with a 70-foot reach, material trailer, heated construction trailer, generator, rescue boat and rigging materials to begin work on the 13 main span hangers over the river. The scaffolding for the land work was being constructed during this job.
Each existing hanger was originally riveted in place more than 60 years ago. These rivets had to be cut off flush and punched out with hydraulic jacks, one rivet at a time. The approach hangers were to be cantilevered off of I-beams placed onto the bridge structure. This was a laborious process which required drilling, alignment of the I-beams and fastening with structural bolts.
Each hanger was adjusted to take its proportional load of the pipeline. On March 15, the job was completed. As a result, there was very little vibration in the pipeline as the bridge flexed under loads. With the new zinc-rich coatings and the use of stainless steel components, the 12-inch pipeline has been repaired, made secure for years into the future.
There are many variables that can negatively affect the progress and outcome of any project. Some are physical like snow and wind while others are abstract like the words on a permit. In every case, a competent contractor should build relationships with the owner of the asset, his customer, the engineers and the regulators. The result will be a successful project completed on time – a project all parties can be proud of.
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