Injection Molded Polyurethane (IMPU)

Increasingly, there is a need to not only protect pipelines from corrosion but also ensure that flow characteristics are maintained within pipelines and flow lines. Thermal insulation is used to make sure adequate flow rates are maintained.

Thermal insulation is applied to the welded joint area, of similar performance to that of the factory-applied line pipe coating, using solid or polyurethane materials by injection molding processes.

Polyurethane materials combine a low overall heat transfer coefficient (OHTC) with the ability to perform at elevated operating temperatures.

PIH has developed and refined the application equipment for the installation of Injection Molded Polyurethane (IMPU) to welded joints.

High-Performance Infill (Concrete Weight Coated Pipelines) Field Joint Coating System

IMPU systems are also used as an infill material for concrete weight coated pipelines where a high degree of impact/compressive load resistance is required. Gravel-filled polyurethane materials provide additional impact resistance and compressive strength.

Key Features of Solid IMPU Polyurethane Field Joint Coating Systems

  • IMPU field joint systems are compatible with thin-film and multi-layer polyethylene and polypropylene factory-applied line pipe coatings
  • Incompressible polyurethane materials suitable for deeper water applications
  • High-impact-resistant polyurethane material for concrete weight coated lines
  • Comparable thermal insulation performance to factory-applied insulation coating
  • Moderate pre-heat required (accelerated curing process)
  • Suitable for field joints including J-Lay collars
  • Little diameter-specific equipment required
  • Fast application and cure times, fast cycle times

Application of IMPU System

  1. Surface preparation and factory coating preparation
  2. Primer layer: Liquid epoxy primer or powder-applied (FBE) primer 
  3. IMPU layer to varying thicknesses

IMPU Equipment
Following application of the primer layer, the polyurethane material is applied by injection into a mold made to the welded joint area parameters: diameter, bandwidth, and material thickness.

The molding process is performed at low pressure, allowing simple lightweight molds to be used. The unreacted polyurethane chemicals are pumped from the coating module (container) to the mold, allowing the container housing the pumps and storage tanks to be situated outside the workstation. Therefore there is no need to accommodate large complex equipment on the firing line, and the equipment can be set up quickly and simply.

The pumping modules incorporate inline monitoring of the application parameters, for enhanced real-time QA.


Pipe Diameter No limit
Voltage 440 V
Current 63 A
Air Consumption 60 CFM @ 120 psi
Weight 3.5 T
Dimensions (L x W x H) 6000 x 2440 x 2440mm


Material Delivery Rates:

Standard Machine = 20 to 100 kg per minute at a ratio of 2:1

High output machine = up to 200 kg per minute