Isolation and weld joint testing of pipelines

Flange weld tester.

Flange weld tester.

Equipment that can satisfactorily seal and isolate pipelines is important as this function is a major requirement during any inspection, maintenance, alteration or repair programme. While the primary function is to test welds, it can also be 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, economic and above all safe in delivering positive and continued isolation while the hot work is carried out. Ideally, as in the case of tyred multi-plugs, it is also capable of hydrostatically testing any new welds afterwards.

IK-PEI Ltd, a specialist engineering company based in the UK, is an established designer and supplier of such 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 labourious and time consuming need to flood and de-water the entire system. Two main styles of tool are available; these are the flange weld tester (see Figure 1) and the internal weld tester. These tools are easy to use and can be operational within minutes with no additional specialist tools or equipment required.

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 that can test at higher pressures is also available, as well as hydraulically operated versions of these testers for the testing of larger diameter pipes.

High-pressure pipe plugs

High-pressure pipe plugs 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 time and cost savings can be made.

The tester can be mechanically locked onto the internal bore of the pipe whilst simultaneously compressing the polyurethane seal with the addition of metallic gripper pads. 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 it is self-energising. Hydraulically operated versions are also available.

Twin-tyre multi-plugs

In the past, achieving positive isolation before commencing any hot work on pipeline systems that carry hydrocarbon resources have 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 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, which allows 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 and 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 remotely operated underwater vehicles. A variation of the high pressure pipe plug can also be used during temporary pigging operations.


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-PEI 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 visit

IK-PEI Limited is a member of the Pipeline Pigging Products and Services Association (PPSA). To find out more on PPSA visit

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