Building pipelines to carry valuable resources such as heat, oil and gas can be a hugely expensive commercial investment. But whether it is a trans-continental oil supply line or a local community district heating system, rigid polyurethane foam plays a vital part in protecting and enhancing the effectiveness of the project.

Huntsman Polyurethanes and Shell Chemicals are two of the world's largest and most respected companies in the manufacture of rigid polyurethane foam systems. One of the benefits of the strategic alliance formed by the businesses in December 1999 was the creation of a major international capability in the specialist sector of pipe insulation. Shell Chemicals retains responsibility for manufacture and development of rigid polyether base polyols, while Huntsman are responsible for all product development, marketing and customer interfaces.

Following the formation of the alliance, Huntsman have at their disposal many years experience and know-how for the formulation of polyurethane foam systems suitable for manufacturing pre-insulated pipes. Huntsman now offers the pipe manufacturing industry state of the art services that includes:

  • the benefits of backward integration, available through the resources of parent company the Huntsman Corporation
  • global access to high quality polyol and isocyanate based polyurethane systems
  • strong fundamental research programmes which help develop new foam systems
  • state of the art levels of technical knowledge and customer support
  • an ability to supply customer specific and tailor made foam systems, suitable for each production line and each pipe manufacturing technique
  • dedicated account management with fast response to customer requirements
  • practical assistance and implementation of crucial environmental, health and safety (EHS) matters and procedures

Rigid polyurethane foam systems for pipe insulation

Rigid polyurethane foam has been used for the insulation and protection of pipes for more than 30 years. It is now more widely used than ever, increasingly displacing alternative materials. One of the most popular areas of use is for district heating systems, where it is the insulant of first choice for many specifiers. Other common uses are in:

  • on and offshore oil and gas pipelines
  • heating and plumbing services for power stations, chemical plants and refineries
  • dairy industry applications
  • district cooling systems
  • special applications i.e. swimming pool pipelines

Polyurethane foam's popularity is based on its outstanding insulation properties, which prevent heat loss, or alternatively maintain temperatures in cold environments to prevent freezing or cracking. These energy conservation qualities improve the overall cost efficiency of customers' networks.

Other important characteristics include high mechanical strength, adhesion, flexibility and good flow-ability, necessary for the consistent fill and insulation of pipe sections.

It is a material with a proven track record for reliability, durability and efficiency. Versatility is demonstrated by the ability to insulate over an extremely wide range of temperatures, from the extreme cold of -196°C to the intense heat of more than 150°C.

It is also suitable for applications ranging from small plumbing pipes 10mm in diameter, up to the largest heating pipes with 2,000mm diameters and 250mm of insulation thickness.

Pipe manufacturing techniques for effective insulation

There are two main forms of pipe production techniques; discontinuous and continuous. The method adopted by an individual manufacturer will reflect the particular operations and applications of that company's business.

Discontinuous pipe manufacturing techniques

Discontinuous manufacture involves filling of the void between, typically, a steel inner pipe within a high density polyethylene (HDPE) casing pipe. The gaps at both ends of the pre-assembly are sealed with tightly fitting caps equipped with injection and air venting holes. Standard steel pipe lengths for this process are 6,12 and 16m.

Continuous pipe manufacturing techniques

There are two main stages of continuous pipe production. In the first, foam is applied to the inner pipe by a molding or spray operation. During the second stage the outer casing pipe is extruded or wound around the pre-shaped foam. This process requires the use of modified polyurethane foam systems to provide different characteristics in terms of reactivity, viscosity build up and cure.

Continuous techniques are mostly suited to bigger pipe manufacturers producing large quantities of the same diameter pipes. Benefits of this approach are its fast and consistent production runs at relatively low variable costs. Material costs can be reduced with lower foam overpack, filling density and casing pipe thickness.

However, changes in pipe diameter and insulation thickness can involve lengthy set up times, which make this a less flexible process than discontinuous manufacture. It is also a higher capital cost technique than discontinuous methods.