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54" Diameter Sewer System Modified Without Service Interruption
The Western Lake Superior Sanitary District was faced with an unusual situation. An upgrade of their 54" pipe system was required near their Duluth treatment plant. Volume in a system this large makes shutdown for repairs unfeasible. The solution would have to ensure that the system continued to operate throughout the upgrade. Working in conjunction with their consulting engineer, RREM, Inc., the Sanitary District selected TDW Services, Inc., of Tulsa, Oklahoma, to handle the hot tapping and line stopping operations. TDW employs a proven technology developed and patented almost 50 years ago by T.D. Williamson, Inc., the parent company.
The project called for installation of a valve on one line and termination and tie in of another. The operation would require four line stops, with the line in service. The plan was to use the TDW Folding STOPPLE® Plugging Machine for the operation. The folding plugging head enters the line through a smaller tapped opening. In this case, a 36" tap handled entry of the 54" plugging heads.
To begin the operation, special line stop fittings were installed on the ductile iron pipe system. Temporary TDW SANDWICH® Valves were placed on each fitting, and hot taps were made.
The folding STOPPLE® Plugging Heads were introduced into the 54" header through the valves, while the bypass provided uninterrupted service to the system. The section of pipe between the STOPPLE® plugging heads was depressurized, opened and modifications performed.
Two Folding STOPPLE® Plugging Machines were placed on the SANDWICH® Valves. To keep the line in service, a temporary 36" diameter polyethylene bypass pipe system was connected between the two plugging machines by Utility Systems of Duluth. When the SANDWICH® Valves were opened, flow was carried in both the 54" system and the temporary 36" bypass system.
With the bypass maintaining flow, the next step was to stop flow and isolate the section of line for scheduled maintenance. The folding STOPPLE® plugging heads were introduced into the 54" header through the valves, while the bypass provided uninterrupted service to the system. The section of pipe between the STOPPLE® plugging heads was depressurized, opened and modifications performed.
Once the pipe modifications were completed and the pipe resealed, pressure was introduced into the work section and the plugging heads were retracted above the SANDWICH® Valves. The valves were closed and the temporary 36" bypass was depressurized and removed.
The SANDWICH Valves, no longer needed at this location, were removed from the pressurized pipeline by TDW technicians. Once the valves were removed and the line was plugged, blind flanges were placed over the fitting outlets. The same process was repeated on a second 54" system located about a mile from the first operation. Again, the valves were removed under pressure and blind flanges installed.
This STOPPLE plugging process, developed by TDW, was the perfect solution for Western Lake Superior Sanitary District. The technology is field-proven and has been used on a variety of pipe systems including steel and concrete cylinder pipe. The largest plugging operation to date has been 96" diameter and the smallest only 3/4".
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