Polyurethane insulation pipe comprehensive analysis

Number of visits：42 seconds Update time：2023-08-22

I. What is Polyurethane Insulated Piping?

Polyurethane insulated pipework is a core component of modern industrial infrastructures, designed for efficient fluid temperature control.

It is used in a wide range of liquid/gas transport systems to significantly reduce heat conduction losses by wrapping a polyurethane foam insulation layer around a metal pipe.

Whether it is the transport of chemical raw materials at sub-zero temperatures or the transmission of high-temperature steam, polyurethane insulated pipes ensure that the temperature of the medium is stabilised in the preset range.

Compared with conventional insulation materials, this technology can reduce energy losses by up to 40 per cent. According to the U.S. Department of Energy, the use of these highly efficient insulation systems in industry can save millions of dollars in operating costs every year.

Next, we'll take a closer look at the technical features and market applications.

II. Core material composition

i. Chemical reaction creates high performance

Polyurethane foams are born from a precise chemical ratio: when polyols are mixed with isocyanates in a ratio of 1:1.05, a violent exothermic reaction is triggered.

This process, which lasts about 30-120 seconds, generates a large number of carbon dioxide bubbles, which eventually form a honeycomb-like closed-cell structure.

With a diameter of about 0.1-0.5 mm, these micropores effectively lock in air - one of nature's finest insulators.

ii. Material Properties Comparison Table

III. Engineering Application Advantages

i. Thermal efficiency revolution

Polyurethane insulated pipes have an R-value (thermal resistance) of 5.6-8.7 per inch, far exceeding that of conventional materials. In the Chicago district heating system, a network of pipes converted to this technology saw heat loss plummet from 15 per cent to 3 per cent.

The secret:

（1）Closed-cell structure blocks heat convection

（2）More than 90% closed cell ratio prevents moisture penetration

（3）Seamless coverage eliminates thermal bridging

ii. Intelligent installation process

Specialist contractors use high pressure spray equipment to create a uniform foam layer 2-50mm thick on the surface of the pipe.

Key control points include:

（1）Surface pre-treatment: to Sa2.5 level of cleanliness

（2）Environmental control: Temperature 15-35°C, humidity <85 per cent

（3）Spraying in layers: no more than 10mm thick at a time

IV. Special Scenario Solutions

i. Underground pipe network experts: direct buried polyurethane heat preservation steel pipe

In the field of municipal engineering, directly buried polyurethane insulation steel pipe has become the first choice for underground pipe network.

Its three-layer structure design is particularly outstanding:

（1）Inner layer: anti-corrosion coated steel pipe (epoxy resin/PE)

（2）Middle layer: 50-100mm polyurethane foam

（3）Outer layer: high-density polyethylene protective jacket

This structure allows the pipe to be buried directly in the ground at a depth of 3 metres without the need for an additional pipe gallery. The construction period was reduced by 40 per cent and maintenance costs by 65 per cent after the technology was adopted for the Boston Municipal Heating Renovation Project.

ii. Customised solutions for industry

For the special needs of chemical plants polyurethane foam insulation pipes can be customised:

（1）High-temperature resistant: ceramic beads are added to withstand 300°C steam.

（2）Anti-corrosion: glass fibre reinforced layer

（3）Ultra-low temperature: graphite particles, suitable for liquid nitrogen transport at -196℃.

V. Economic and environmental benefits

i. Full Life Cycle Cost Analysis

Although the initial investment is 30-50% higher than conventional insulation, the difference is recovered in 3-5 years of operation.

Typical calculation models show:

（1）Energy savings: $12.6/linear foot per year

（2）Maintenance costs: 75% lower

（3）Service life: 2-3 times longer

ii. Sustainability Practices

Leading manufacturers are advancing environmental innovations:

（1）Replacing HCFCs with HFO blowing agents (99.9% reduction in GWP)

（2）Developing bio-based polyurethanes (30% raw material from plants)

（3）Establishing closed-loop recycling systems (85% reuse of old pipe foam)

VI. Industry Application Mapping

i. Energy sector

（1）Oil and gas pipeline: after the adoption of the Alaska pipeline, the temperature fluctuation of crude oil delivery is controlled at ±2℃.

（2）Liquefied natural gas: Cooling efficiency increased to 98.7 per cent.

ii. Building HVAC system

New York Hudson City Plaza project using the technology to achieve:

（1）32 per cent energy savings in air conditioning systems

（2）90% reduction in duct condensation problems

（3）40 per cent smaller footprint

VII. Polyurethane insulation pipe standard analysis

i. Chinese national standard

（1）GB/T 29047-2012

        It is applicable to prefabricated directly buried thermal insulation pipe for conveying medium temperature ≤120℃ and peak temperature ≤140℃, covering the technical requirements of working steel pipe, polyurethane thermal insulation layer and polyethylene outer sheath, and clearly stipulating key parameters such as axial shear strength (≥0.12MPa) and closed hole ratio (≥88%).

（2）GB/T 29046-2012

       For the testing method of urban heating pipelines, it requires the density of heat insulation layer ≥60kg/m³, compressive strength ≥0.3MPa (under 10% deformation condition), and regulates the performance of high-density polyethylene material for the outer sheath (tensile strength ≥19MPa, elongation at break ≥350%).

（3）CJ/T 114-2000

       The industry standard is supplemented with the formula for calculating the deviation of pipe outer diameter and wall thickness, e.g., when the outer diameter is ≤400mm, the deviation = 0.1×wall thickness+0.2, to ensure the consistency of production.

ii. European standard

EN 253:2021

The mainstream standard for underground heating networks in Europe, stipulating that the overall prefabricated system consisting of a working steel pipe, polyurethane insulation and polyethylene jacket requires a continuous operating temperature of ≤120°C, a peak temperature of ≤140°C and a service life of ≥30 years.

Its technical parameters include:

（1）Closed hole rate of insulation layer ≥90%

（2）Density of outer sheath ≥950kg/m³ (20℃)

（3）Axial shear strength ≥0.12MPa.

iii. American Standard

Common standards for the US market include:

（1）ASTM C591: regulates the physical properties of rigid polyurethane foam, such as thermal conductivity ≤ 0.028W/m-K.

（2）ASHRAE 90.1: deals with the requirements for insulated piping in the energy efficient design of buildings [citation: User History Dialogue].

iv. Japan and Germany

（1）Japan mostly refer to JIS A 9511 (rigid polyurethane foam insulation material standard).

（2）Germany adopts DIN EN 253 in line with the European Union standard, combined with DIN 30670 to strengthen the anti-corrosion performance of the outer protection pipe.