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White Paper - T.D. Williamson, Inc.

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2ABSTRACTDouble Block and Bleed (DB&B) is the preferred approach used tomaximize safety while performing piping maintenance. The aim of thepaper is to outline an innovative method of achieving DB&B on gaspipelines.DB&B is traditionally achieved by one of several methods, for example,through using two (2) valves, a valve and a STOPPLE ® plugging head,a STOPPLE ® plugging head and an isolation plug or tandemSTOPPLE ® plugging heads. There are also several DB&B methodswhich utilize inflatable bags or bladders.Developed by T.D. <strong>Williamson</strong> (TDW), the patented STOPPLE ® Trainsystem is a new tool that links together two (2) STOPPLE ® pluggingheads. Only one (1) hot tap is required in the piping for which theSTOPPLE ® Train is inserted. The first STOPPLE ® plugging head is thetrailing plugging head and forms a primary seal. The initial STOPPLE ®plugging head to enter the pipe forms a secondary seal while the backplugging head forms the primary seal. Once sealed, the bleed isaccomplished through a relief port located between the plugging headsallowing downstream maintenance to commence.1.0 INTRODUCTIONOn 20 November 2008, a Texas gas pipeline needed to be replaced.Part of the safety requirements included a DB&B method of pipelineisolation. To add to the complexity of the job, the pipeline was next to avery busy street. Because of rush hour traffic, the pipeline could onlybe repaired between the hours of 9am to 4pm. In addition, otherrequirements of the customer included minimized intrusion into piping,lower fitting, welding Time and associated costs. In response to therequirements and for DB&B isolation, the STOPPLE ® Train pluggingsystem was deployed.2.0 TRADITIONAL METHODS OF DOUBLE BLOCK AND BLEEDIn the past, pipeline operators have used a number of differentmethods to achieve DB&B. For example, two separate valves with ableed port between them can achieve this. Or, the combination of avalve and a plugging head with a port between them can work, as canthe tandem of a plugging head and an isolation plug with a portbetween them. Many operators have simply used two plugging headsand a bleed port. What all of these methods have in common is the

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