12. November 2014

Isolation and weld joint testing of pipeline

Introduction

For a long time now, equipment that can satisfactorily seal and isolate pipelines has been in great demand as this function is a major requirement during any inspection, maintenance, alteration or repair program. The primary function is to test welds, but sometimes it is also necessary to carry out hot work and the isolation of systems that are no longer required.

The requisite tool must be reliable, simple-to-use, economical and above all safe in delivering positive and continued isolation whilst the hot work is carried out. Ideally, as in the case of Twin Tyred Multi-Plugs, it is also capable of hydrostatically testing any new welds afterwards.

IK-UK Ltd, a specialist engineering company based in the UK, is an established designer and supplier of Pipeline Isolation and Testing Equipment.

Flange Weld Testers and Internal Weld Testers

Weld Testers enable operators to perform localised pressure testing of new or existing flange welds, negating the often laborious and time consuming need to flood and dewater the entire system. Two main styles of tool are available; these are the Flange Weld Tester (fig 1) and the Internal Weld Tester (fig 2). These tools are easy to use and can be operational within minutes and there are no requirements for any additional specialist tools or equipment.

The main safety feature of the Flange Weld Tester is that a central by-pass port allows the operator to monitor the downstream conditions. Specially designed polyurethane seals allow greater radial clearance where the weld bead is excessive, a feature that also allows the unit to seal in pipes suffering from pitting. Standard test pressures of up to 230 barg can easily be achieved and equipment is also available that can test at higher pressures. Hydraulically operated versions of these testers are also available for the testing of larger diameter pipes.

 

High Pressure Pipe Plugs
High Pressure Pipe Plugs (fig 3) can be used when a weld or joint needs to be hydrostatically tested on an open pipe or vessel. As the need to weld caps or flanges to the pipe is eliminated, considerable savings can be made in time and costs. The addition of metallic gripper pads allows the tester to be mechanically locked onto the internal bore of the pipe whilst simultaneously compressing the polyurethane seal. The pipe can now be filled with water through a centre by-pass port on the plug, and when used in pairs, the by-pass port on the second plug will allow the venting of air from the pipe. An added safety feature with this design is that the plug is self-energising. Hydraulically operated versions are also available.

Twin Tyre Multi-Plugs
Achieving positive isolation before commencing any hot work on pipeline systems that carry hydrocarbon resources has in the past proven to be problematical, with the use of air bags and compression plugs being common practice. Unfortunately, such methods have a history of unreliability with little guarantee of successfully creating a safe working environment.
The Twin Tyred Multi-Plug (fig 4) is a variation on an established theme that boasts a double isolation feature through the efficient use of two inflatable tyres. Incorporating some of the features of weld testers, these tools allow the operator to create an effective seal allowing hot work to proceed. The same tools also facilitate efficient hydrostatic testing of the weld or repair work.
Recent Developments in Isolation Equipment
Flange Weld Testers and Internal Weld Testers are now available that allow the isolation and testing of welds in 90 degree elbows. Also available are Abandonment Plugs that have been specifically designed for the permanent sealing and isolation of both dormant and decommissioned pipelines with Sub-Sea versions specifically designed to be used by divers or ROVs. A variation of the High Pressure Pipe Plug can also be used during temporary pigging operations.

 

Summary
The safe and reliable sealing and isolation of pipework is of extremely high importance when undertaking any work on pipeline systems. The correct choice of safe, effective and economical equipment must be subject to rigorous and informed evaluation. IK-UK Ltd has significant expertise in both the design and provision of sealing and isolation solutions, both standard and custom built, that satisfy the tough demands of the modern pipeline industry. A wide range of plugs and testers are available to suit most requirements ranging from atmospheric to high pressure applications.
For more detailed information on pipeline isolation and testing, please visit www.ik-worldwide.com

 

By Peter Mahoney, engineering and contracts manager, IK-UK Limited