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This illustrates the valve being lowered on the fitting, the coupon to the side, and TDW's Model 1220 Folding Head Plugger that was used to plug the line.
Tapping and plugging a water line that has been in the ground for years is something like renovating a 100 year-old home. The renovator never knows what he's going to find on the other side of that wall until he opens it — in this case, the pipe wall. In order to size a plugging head to fit inside the pipe and seal against the pipe wall to stop flow, the technician has to know the pipe's inside diameter. He comes onto the job with a pretty good idea, based on size of the pipe and specifications provided by the customer. Components necessary to adjust the plugging head size to fit thin- to thick-wall pipe are brought to the site. Confirmation of the actual inside diameter is not made until the tapped coupon is removed and the wall thickness measured.
The surprises found by a technician when he removes the coupon can sometimes turn a routine plugging job into something much more than routine — just like the problems the home renovator finds on the other side of his wall. The difference is things are critical with the technician. Once the tap is made, the line has to be plugged, the work done, and the line restored to service so the community downstream can have water. The house renovation can wait while solutions are found.
Such was the case in northern Oklahoma with an 18-inch carbon steel transmission line carrying water from deep wells to the city's water treatment. The 18-inch line tied into a valve, which had aged and no longer worked, on a 27-inch line. Water from the larger line was backfeeding through the inoperable valve into the 18-inch line. With the 18-inch line plugged and pumps at the wells shut down, the line could be drained. At that point, it would be cut and a new line tied in, bypassing the faulty valve and leading directly to the treatment plant.
A 12-inch hole was tapped through a 12-inch fitting welded to the pipe. TDW Services Technician, Jim Treece, used the Model 1220 Folding Head Plugger to plug the line, shown at right. This machine is capable of plugging 12- to 20-inch pipe through a 12-inch tapped hole. It uses a folding plugging head which is opened hydraulically against the pipe wall after insertion into the line through the smaller tapped hole.
One look at the tapped coupon told Treece this would not be the routine plugging job he had expected. Scale and corrosion deposits were more than a quarter-inch thick on the inside pipe wall and were not consistently even around the wall. These deposits significantly reduced the inside diameter, and it would be tough getting the plugging head to open. Once opened, it would also be difficult to get the sealing element to conform to the extremely corroded wall.
If, when opened, the plugging head would break the corrosion loose from the pipe wall, it just might open to the full position. However, working it back and forth against the rough scale also might cut and tear the Neoprene sealing element, reducing its capability to seal against the pipe wall.
The Model 1220 plugging head is maneuvered into position in the pipe by a combination of lowering, tilting, opening and closing of the plugging head. All of these functions are performed hydraulically, and each one affects the capability of doing the others. They are all interrelated, so it is a matter of continually making minor adjustments to each function until the plugging head is open and in sealing position. On pipe with no buildup on the inner wall, the operation is routine, but not in this case. After several attempts, the plugging head would not open to its full position. Treece retracted the plugging head, closed the tapping valve, then removed the plugging machine. Examination revealed that the sealing element badly gouged where it came in contact with the pipe wall. He removed the sealing element and pusher plates, which were attached to the plugging head underneath the sealing element and designed to force the sealing element against the pipe wall.
A slightly smaller sealing element was attached to the plugging head and the machine was reinstalled on the tapping valve. The plugging head was once again lowered into the pipe and the up-down, tilt, and open-close jockeying of the plugging head resumed. After 15 minutes, the right combination of functions was found, and the plugging head opened and a seal was made. The plugging head was locked in position, the line drained and cut, and the new tie-in made. On completion of work, the plugging machine was removed and a completion plug was installed in the neck of the tapping fitting. This permitted removal of the tapping valve. A blind flange was then bolted to the fitting, finishing the job. For more information about TDW Services, Inc., and our capabilities to tap and plug old pipe, contact us a 800-828-1988 or 1-918-447-5100.
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