T.D. Williamson, Inc. (TDW) has completed the first-ever subsea STOPPLE® Train isolation. The patented STOPPLE® Train plugging system links two plugging heads into a “train” capable of providing the added assurance of double block at each isolation point. The double isolation was performed in about 60 feet of water in the Gulf of Mexico to facilitate abandonment and decommissioning of an old platform.

In the past, pipeline operators used a number of different methods to achieve double block functionality. These methods typically required more than one hot tap and fitting to achieve a double block, but the STOPPLE® Train plugging system requires only one tap and fitting. Its linked plugging heads can be inserted into a line through just one opening. A single hot tap and fitting yields the double block benefit of two separate in-line plugs.

Double block was critical in this case. A platform was being abandoned, requiring the removal and replacement of a section of pipeline. The pipeline section came up as a riser, crossed the platform and returned down as a riser before continuing. Both of the risers and the platform section of the line needed to be removed.

The line was bled down to 0 psi, then two 12-inch STOPPLE® Train systems were inserted – one on each side of the section to be removed – to prevent seawater, sand and organic debris from entering the hundred-mile line when the section of the pipeline was cut out.

“The STOPPLE® Train system was ideal because the line in question was a non-piggable sales gas line,” says Calvin Schmidt, Senior Sales Representative for TDW. “It was very important not to flood the line. The dual seals of each STOPPLE® Train plugging system ensured that the line was isolated and would not flood.”

Once the new piping was successfully installed, the seawater between the two plugging systems was evacuated and replaced with warm nitrogen to absorb and remove moisture. Following removal of the plugging heads, the pipeline was re-energized and placed back into service.

The STOPPLE® Train plugging system was introduced in 2008. An initial wave of five plugging head sizes (4- through 12-inch) were specifically designed to cover about 80 percent of hydrocarbon processing industry applications. In response to requests from pipeline operators who also sought the value of double block and bleed, a second wave of sizes (including 16- and 24-inch) has been tailored to cover about 80 percent of pipeline market needs. Additional sizes (20- and 30-inch) are due by year’s end. To date, more than 80 piping and pipeline isolation projects have been performed using the system.

Tags: Inc., T.D. Williamson