A medical center in Honolulu, Hawaii, planned to build an underground parking garage but there was one problem. Along the entrance of the proposed garage ran a 42-inch potable water line owned by the Municipal Board of Water, city of Honolulu. The line would have to be lowered to make room for the garage.
The Municipal Board of Water in Honolulu services approximately 800,000 people. It is one of the 10 largest water utilities in the country.
TDW Services Inc., of Tulsa, Okla., was called in to help. Because the line was critical to the community, it had to remain in service during the operation. The plan called for double line stops (temporary plugging) with a bypass.
TDW tapping and Stopple? Plugging equipment, including tapping valves and fittings, were shipped to the job site. Since the equipment was to be used on a potable water line, it was sanitized before shipping. All petrochemical lubricants were removed and common cooking oil was used in its place. At the job site, before equipment was installed on the line, it was further sanitized with a chlorine spray to kill bacteria.
During the first phase of the project, mechanical, full-circumference 42x36 inch reduced-branch Stopple fittings were bolted to the 42-inch cast iron water line on either side of the work area, approximately 200 feet apart. An o-ring around the neck of the fitting sealed it against the external pipe wall. Each fitting was then encased in cement for stability, keeping it from rotating on the pipe due to the weight of the Stopple plugging equipment. The concrete also compensated for thrust forces caused by water flowing through the line.
Next, 36x36x36 inch spool adapters were bolted onto the fittings. The 36-inch side outlet provided the connection for the temporary bypass. Thirty-six-inch Sandwich? Tapping Valves were bolted onto the fittings, and the 200-foot bypass line was then installed to route flow around the work area.
A TDW Model 1200 Tapping Machine was installed on the fitting and tapping began. The 36-inch circular cutter cut through the 1.125-inch wall thickness in about three hours. The coupon, the circular piece cut from the pipe, was retained by the cutter. With the bypass valves open, the 200-foot bypass was placed in partial operation when the cutter first cut through the main line.
When the two taps were completed, the Stopple Plugging Machines were installed on each fitting. The folding plugging heads were lowered into the line and opened, sealing against the pipe wall and stopping flow. Now the work area was isolated and the bypass was in full operation, rerouting water to the community without interruption. The isolated section was drained, cut out and the line lowered.
When the lowered line was installed, the folding plugging heads were retracted and water began to flow. The bypass was closed, but the Stopple equipment remained on the line for an additional 24 hours to ensure no problems existed in the new section. The plugging machines were removed, completion plugs were installed.
The entire job, including tapping and temporary line stopping, cutting, lowering and re-installing the 200-foot section, and removing all equipment, including the bypass and associated valves, required only 10 days to complete.
