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Pipe – in– Pipe sealing systems are typically designed to isolate a section of flooded annulus by preventing water passage between adjacent pipe-in-pipe assemblies. EXSTO typically manufactures 3 different types of Pipe-in-Pipe Protection:

  • Bolt activated Waterstops (figure 1)
  • Pressure activated Waterstops (figure 2)
  • Bulkhead Seals (figure 3)

Bolt activated seals are preferred for applications where the pipelines have a high range of tolerances and have a wider range of sealing capacity. Pressure activated seals offer ease of installation when pipeline tolerances are known to be more accurate and are more suited to high level pressure environments, due to their inherent pressure activated mechanism. Bulkhead seals are another bolt activated sealing solution offering additional structural support.


The products are manufactured from low viscosity, two component polyurethane systems (typical hardness range 75 Shore A). The polyurethane elastomer compound has a proven track record for this type of application being specified for a number of pipe-in-pipe projects (e.g. Shell Starling & BP Rhum).

The design parameters can be changed to accommodate a wide range of size and pressure differential requirements. Calculations are performed to estimate amongst others:

  • Sealing capacity
  • Seal push-out force
  • Required compression/expansion

The following parameters (typical) are needed to design PIP protection systems:

  • Pipe dimensions including tolerances
  • Differential Pressure requirement
  • System operating temperature
  • Design life
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