Isolation is a key part of safe, effective pipeline maintenance, repair, and testing jobs. It involves cutting off the flow to a particular section of the pipeline and can be done while the system is operational or offline. Once the flow is stopped and the section isolated, work can be completed on it, or it can be replaced. There are several different methods used to create an effective pipe seal, including double block and bleed pipe plugs, mechanical isolation plugs, mechanical line stop plugs, inflatable plugs, and insertion valves. 

When is pipeline isolation necessary? 

Isolating a section of pipeline is required by a wide variety of repair and maintenance tasks in low, medium, and high pressure environments. Here are the most common reasons to stop flow through a section of a pipe:

  • Sectional pipeline replacement 
  • Valve repair and replacement 
  • Pipeline tie-in and bypass projects
  • Pipe abandonment or decommissioning jobs 
  • Mid-line pipeline repair 
  • Pressure and leak testing 

How to isolate a pipeline section 

Double block and bleed pipe plugs – Double block and bleed (DBB) plugs feature dual sealing surfaces that create a barrier against pressure from both directions when the valve is closed. They also incorporate a mechanism for venting or draining the space between these sealing surfaces. DBB plugs are frequently employed to ensure complete isolation of process fluids from other equipment. By using these pipe plugs, the potential for harm to personnel and the environment can be minimized. In scenarios involving short term work at medium to high pressures, DBB plugs are often regarded as the minimum acceptable standalone isolation method.

Inflatable line stop plugs – Inflatable plugs is a fast, easy method of isolating a section of pipeline. They are deployed through a non-size-on-size completion flanged line stop fitting, as opposed to their mechanical counterpart, which requires a size-on-size fitting. Inflatable plugs aren't affected by pipe concentricity, geometry, orientation, or internal condition. As they inflate, they conform to the pipe shape, offering a larger sealing surface area than mechanical options. They require smaller, lighter equipment for insertion, resulting in a more compact footprint. Plus, the same equipment can be used for various plug sizes.

Mechanical line stop plugs – Mechanical line stop pipe plugs are one of the most commonly used methods to isolate a section of pipeline for maintenance or repairs without disrupting the entire system. They're inserted through a same size completion plug flanged line stop fitting. Unlike inflatable options, mechanical pipe plugs are preferred for low to high pressure and medium to high temperature applications. They're limited to straight pipe runs with concentric, circular internal diameters. Their robust design withstands high pressures and, when used in pairs, can handle low to medium flow rates. They're suitable for medium to long term isolation.

Insertion valves – Providing a permanent line isolation solution, insertion valves are installed through a bolt on fitting on the pipe, followed by a hot tap while the system is operational. The valve bonnet/gate cartridge is then inserted through the fitting nozzle and secured, allowing for full valve operation. Various types and models exist, mostly used in low to medium pressure water, wastewater, or non-critical services. Pipe integrity, geometry, and multiple other factors are all considered when selecting this option.

At Petersen, we offer a wide variety of inflatable double block and bleed and line stop plugs. For mechanical line stops pipe plugs and permanent insertion valves, there are a variety of manufacturers. Contact our team to find the best standard or custom solution for your project! 

 

Disclaimer: The information may be used but with no warranty or liability. This information is believed to be correct but should always be double checked with alternative sources. Strictly adhere to and follow all applicable national and local regulations and practices.

Regardless of these comments, it is always necessary to read and understand manufactures instructions and local regulations prior to using any item.