Injection Molded Polypropylene (IMPP)

As deeper-water offshore fields are developed, pipeline operating parameters become more and more challenging. Deeper water has seen the use of advanced pipe coating materials. Multi-layer polypropylene systems are widely used in order to provide adequate thermal insulation to maintain flow characteristics within pipelines and flow lines.



Following welding of line pipes, thermal insulation is also applied to the welded joint area of similar performance to that of the factory-applied line pipe coating. Injection Molded Polypropylene (IMPP) thermal insulation is widely used, combining a low overall heat transfer coefficient (OHTC) with the ability to perform at high operating temperatures (140°C).


PIH’s IMPP equipment and processes are designed and manufactured specific to project parameters and requirements:


  1. Thickness (U values) and bandwidth (volume of material)
  2. Firing line or workstation configuration and footprint
  3. Installation target cycle times


PIH hosts a team of engineers and technicians dedicated to delivering a range of IMPP solutions for welded joints and custom fittings (bends, spools, pipes).

PIH has gained extensive experience in installing the IMPP system as part of offshore pipe laybarge operations for both S-Lay and J-Lay configurations and at onshore spoolbase locations.

PIH’s IMPP equipment and processes are also used at fabrication yards for application of IMPP to spools. Project experience also includes application of IMPP to
bends and fittings.



Key IMPP Features

  • IMPP field joint systems are compatible with thin-film and multi-layer polypropylene factory-applied line pipe coatings
    • Standard thin-film 3-layer polypropylene coating
    • Multi-layer polypropylene systems
  • Incompressible polypropylene materials suitable for deeper water applications
  • Comparable thermal insulation performance to factory-applied insulation coating
  • Suitable for operating temperatures up to 140°C
  • Suitable for field joints including J-Lay collars

Application of IMPP

PIH has developed equipment and processes for the efficient application of the IMPP system.

The IMPP System


  1. Surface preparation and factory coating preparation
  2. Primer layer: Fusion Bonded Epoxy (FBE) powder and co-polymer layers
  3. Pre-heat factory coating (chamfer and overlap area)
  4. IMPP of varying thicknesses (U value)
  5. Quench

IMPP Equipment and Processes
Following application of FBE and the co-polymer layer, the factory coating is prepared and heated using PIH’s patented heating system.


The polypropylene material is applied by injection into a specialist mold made specifically to the welded joint area parameters: diameter, bandwidth, and material thickness.


The molds incorporate inline cooling to optimize curing for adequate “roller load” properties.


PIH’s IMPP team engages early in project discussions with the client to understand project deliverables and to develop the optimum equipment and processes for the project.


PIH manages PQT trials and testing, through to project delivery.


IMPP Equipment Specifications
PIH has available standard and bespoke IMPP equipment and processes. Please consult the PIH IMPP team for technical information.