Cold and Cryogenic Pipework: Ensuring Effective Insulation
Cold and Cryogenic Pipework: Ensuring Effective Insulation
In recent years, the move to diversify Europe away from Russian gas imports has seen increased investment in new LNG port infrastructure and expansions to existing facilities. At the same time, ongoing economic uncertainties mean there is considerable pressure to limit the expenditure (CAPEX) on new projects, both within the LNG industry and across the wider petrochemical sector. This can lead to compromises in aspects of the design and specification which could significantly impact the long-term profitability and even viability of these facilities.
One area where this can be particularly damaging is in technical insulation for cold and cryogenic applications. Where the quality of these systems is compromised, it can lead to a range of issues which could considerably increase operational costs and carbon impact. These include higher boil-off losses as a result of heat gains, and increased risk of ice formation which can accelerate wear and tear, leading to additional maintenance and repair costs. At the extremely low temperatures at which these systems operate, these issues will often present themselves rapidly, potentially leading to significant downtime and remedial costs soon after sites go live.
These potential risks and long-term costs need to be carefully considered as part of the specification processes for the pipework insulation. Polyisocyanurate (PIR) insulation materials offer a proven solution for low temperature pipework, delivering leading thermal performance which can help to reduce the thickness or number of layers of insulation needed to effectively insulate cold and cryogenic pipework. These products can also be manufactured to provide high dimensional stability and low water permeation and absorption, helping to support long-term performance.
To ensure successful installations and support inspection and maintenance practices, some manufacturers also now offer dedicated training on these insulation products for installers and maintenance staff.
What are the key considerations when insulating LNG systems?
The cryogenic pipework systems used as part of LNG port facilities present a range of specific challenges which need to be considered when specifying insulation.
For example, these facilities often incorporate large diameter pipework which can run to lengths of several hundreds of metres. This pipework and the connected systems must be maintained at a constant low temperature (-162°C or lower in the case of LNG) to perform efficiently. Even relatively minor heat gains in any area of the system can lead to the liquid returning back to its gaseous state. Dealing with this unintended boil-off can present significant issues for operational teams, and cooling the gas back to a liquid state can place significant additional demand on refrigeration systems, raising both operational carbon and energy costs. The alternative of venting the gas to prevent overpressure means wasting valuable resources.
To prevent this boil-off, it is not only necessary to achieve a continuous physical layer of insulation across all elements within the system, but the insulation must also provide a consistently excellent level of thermal performance.
Maintaining this consistency of thermal efficiency in combination with a continuous outer vapour barrier is also essential to reduce the risk of moisture ingress and ice formation on the pipework. Ice can add loading to the system, potentially damaging components, and as it expands it can create gaps within the insulation layer, exposing more pipework and further exacerbating the issue.
To avoid this, it is not only essential to ensure best practice during installation, but the products themselves must also offer sufficient compressive strength to withstand long-term compressive forces by thermal contraction and the typical impacts which may occur as workmen carry out day-to-day maintenance and repair works.
With many of Europe’s LNG ports being located in warmer locations, and the risk of prolonged extreme summer temperatures rising as a result of climate change, it is essential that the insulation materials are dimensionally stable and can provide effective resistance against the thermal stresses which can occur as a result of the temperature differential between the very low temperature pipework and the outer ambient temperatures.
If the insulation products used provide insufficient stability, this can lead to them warping over time because of these stresses, creating gaps in the insulation layer. This can not only result in ice formation and increased boil-off rates, but also requires costly insulation replacement works to be carried out which may require system downtimes.
All of these factors mean that the choice of insulation is a crucial factor for any LNG project.
How to select effective insulation
When choosing insulation for this demanding application, the thermal conductivity (also known as lambda value) of the insulation is perhaps the most fundamental consideration. The lower the thermal conductivity, the more effective the insulation will be at preventing heat gains. The thermal conductivity of insulation materials can be impacted by the density and thickness of the insulation and the operating temperature for the system. This information should be provided within the product declaration of performance (DOP) document as a thermal conductivity curve.
Polyisocyanurate (PIR) insulation materials have some of the lowest thermal conductivities of any commonly used insulation materials for cold and cryogenic pipework applications. This performance means that it is possible to effectively insulate the pipework with a slimmer thickness of insulation than might be possible with worse performing alternatives. In addition to providing practical benefits during installation, this can reduce the overall circumference of the insulated pipework, potentially leading to savings in size and cost of associated ancillaries and cladding.
With its homogeneous polymer, PIR insulation offers good levels of compressive strength, helping to resist the risk of compression either from long-term external pressure on the insulation or through accidental point impacts during routine maintenance work. This is a key requirement for industrial applications, as any compressive failures can degrade the thermal performance of the insulation layer, also leading to unwanted heat gains.
The closed cell structure of PIR insulation also limits water vapour permeation. This is a key concern for cryogenic applications as the vapour pressure at the cold pipe is much lower than in the surrounding air. This vapour pressure differential can cause water to be drawn into the insulation. In combination with primary and secondary vapour barriers which have been accurately installed to provide continuous barrier layers, this closed cell structure can help to restrict vapour ingress and support system lifespans. In addition, the closed cell structure also limits water absorption into the insulation.
PIR insulation also provides a high level of dimensional stability. This allows it to withstand thermal stresses, due to the significant temperature differentials between the pipe contents and outer ambient environment, without warping or distorting – supporting consistent long-term performance and lifespan of both the pipework and insulation.
The rigid PIR insulation sections provide a number of practical benefits during fabrication and installation. The insulation is less fragile than some other commonly used cryogenic pipe insulation products, meaning it is less likely to be damaged during cutting and installation. Its low thermal conductivity can reduce the required insulation thickness, providing space savings which can aid installation, inspection and maintenance.
The combination of these different benefits makes PIR insulation products well suited for use on cold and cryogenic pipe applications. In practice, this is evidenced by their continued performance for over 20 years with minimal maintenance on a number of global LNG facilities, delivering long-term savings over the initial investment.
Workmanship and inspection – driving lifetime value
In addition to the choice of material, ensuring accurate installation of cold and cryogenic insulation materials is crucial to long-term performance of LNG facilities. These installation works should be carried out by contractors who have sufficient experience and training in these specific systems to understand best practice requirements.
This includes ensuring that all joints are tightly butted across the full length of pipework to ensure a constant layer of insulation. Longitudinal joints should be offset between the different layers of insulation to provide a longer path for heat or moisture ingress. Appropriate high-density insulation should be fitted at pipe supports, anchors and hangars, preventing compressive failures at these points. Vapour barriers, vapor stops, and seals must also be applied in line with manufacturer guidance to ensure a continuous vapour barrier and prevent moisture ingress.
In the long term, it is essential that maintenance staff are familiar with the signs which could indicate a potential issue with the insulation system. These include ice build-up, damage to the insulation and/or outer vapour barrier and any obvious distortion of the insulation or pipework. By addressing these issues quickly and effectively, it should be possible to safeguard the lifespan of these systems.
To support both installers and maintenance/inspection staff, some cold and cryogenic pipe insulation manufacturers now provide dedicated training courses covering the key considerations when insulating these systems and best practice for both installation and inspection.
Safeguarding your investment
The construction and extension of LNG facilities represents a considerable upfront and long-term investment. To provide the optimal long-term returns on these investments, and support compliance with key regulations around carbon emissions, it is crucial that cold and cryogenic pipework are effectively insulated and that these works are carried out to a high standard by trained professionals.
PIR insulation systems provide a high-performance solution for these applications, supporting both system efficiency and the ease and speed of installation. In combination with the dedicated training services offered by some manufacturers, this can facilitate the efficient long-term operation of LNG facilities.