Super Insulation Technology

14 May 2023

By: Howard Chan

Q: How many types of super-insulation technology are there in the market?

A: There are several types of super-insulation technology available in the market. Some of the most common types include:

1. Multi-Layer Insulation (MLI): This technology uses multiple layers of thin, reflective materials to create a high-performance insulation system.

2. Aerogel Insulation: This technology uses a lightweight, highly porous material to create a low-density insulation system that offers excellent thermal performance.

3. Vacuum Insulation Panels (VIPs): These are highly insulated panels that use a vacuum to minimize heat transfer.

4. Foam Insulation: This technology uses a foam material, such as polyurethane or polystyrene, to create a high-performance insulation system.

5. Phase-Change Material (PCM) Insulation: This technology uses materials that can absorb and release heat during phase changes, such as melting and freezing, to maintain consistent temperatures.

Each type of super-insulation technology has its own unique advantages and disadvantages, and the best choice will depend on the specific application and performance requirements.

Q: What type of MLI is used in cryogenic insulation?

A: The Multi-Layer Insulation (MLI) used in cryogenic insulation is typically a modified version of the standard MLI used in high-temperature applications. While the basic principles of MLI are the same, there are some key differences in the design and materials used to optimize it for use in cryogenic environments.

One key difference is the use of lower-emissivity materials in the MLI layers. In cryogenic applications, the temperatures are much lower than in high-temperature applications, which means that even small amounts of radiation heat transfer can have a significant impact. By using materials with lower emissivity, the MLI layers can reflect more of the radiation heat transfer and minimize heat loss.

Another important factor is the number and thickness of the MLI layers. In cryogenic applications, the MLI may need to have more layers than in high-temperature applications to achieve the desired level of insulation. Thicker MLI layers may also be used to minimize heat transfer via conduction and convection.

Finally, cryogenic MLI may also be designed to be more flexible and durable than standard MLI to withstand the extreme cold temperatures and the thermal cycling that can occur in cryogenic environments.

Overall, cryogenic MLI is designed to provide the same high-performance insulation as standard MLI, but with modifications to optimize it for use in very low-temperature applications.

Q: How does MLI works in super insulated system?

A: Multi-layer insulation (MLI) is a type of super-insulation technology that uses multiple layers of thin reflective sheets or films to achieve very high levels of thermal insulation. MLI is also commonly used in spacecraft, satellites, and other applications where weight and space are at a premium.

The basic principle of MLI is simple: each layer of reflective material helps to reflect back thermal radiation, which can greatly reduce heat transfer by radiation. The layers of reflective material are typically separated by spacers or support structures to prevent contact between the layers, which could otherwise result in thermal bridging.

The effectiveness of MLI depends on several factors, including the number of layers used, the thickness of each layer, the spacing between the layers, and the emissivity of the reflective material. Generally speaking, the more layers and the lower the emissivity, the better the insulation performance.

One of the key advantages of MLI is its very low thermal conductivity. Because MLI is designed to prevent heat transfer by radiation, it is less affected by changes in temperature than traditional insulation materials like foam or fiberglass. MLI can also be very lightweight and compact, making it ideal for space applications where weight and volume are critical.

However, MLI can be more difficult to manufacture and install than traditional insulation materials, and can also be more expensive. 

Despite these challenges, MLI-based super-insulation technology has proven to be highly effective in a variety of applications, from spacecraft to cryogenic storage tanks. Ongoing research and development in this field is likely to lead to further improvements in insulation performance, as well as new applications for MLI-based materials and techniques. 

To ensure accurate heat leak calculations during the design of a cryogenics system, it is crucial for the manufacturer to conduct tests that determine the apparent thermal conductivity value of the Multilayer Insulation (MLI) and provide this data. 

By conducting these tests, the manufacturer can obtain precise measurements of MLI's thermal conductivity, which is essential for calculating heat leaks accurately. This information plays a critical role in designing a cryogenics system that effectively minimizes heat transfer and maintains the desired temperature levels.

Therefore, it is of utmost importance that the manufacturer prioritizes these tests and shares the resulting data. By doing so, they enable engineers and designers to make informed decisions when selecting the appropriate MLI and optimizing the system's thermal performance.

In conclusion, the manufacturer's commitment to conducting tests and providing accurate data on MLI's apparent thermal conductivity is a vital step towards ensuring the efficient and reliable operation of cryogenics systems.

Q: Is vacuum level an important factor in super insulation? How does it improves the MLI performance in super insulated system?

A: Vacuum plays a critical role in improving the performance of MLI-based super-insulation technology. When a vacuum is created between the layers of reflective material in an MLI blanket, it greatly reduces heat transfer by conduction and convection, as there are no air molecules present to carry heat energy.

By reducing heat transfer through conduction and convection, the vacuum in an MLI blanket can greatly enhance its overall thermal performance. This is because the primary mode of heat transfer in MLI is radiation, which is not significantly affected by the vacuum.

The vacuum also helps to minimize thermal bridging between the layers of reflective material, as there are no spacers or support structures needed to maintain separation between the layers. This can further enhance the insulation performance of the MLI blanket.

In addition to improving the thermal performance of MLI-based super-insulation, the vacuum can also make the insulation lighter and more compact. Without air molecules present, the overall density of the insulation can be greatly reduced, making it easier to transport and install.

However, creating and maintaining a vacuum in an MLI blanket can be challenging. Even small leaks or breaches in the vacuum envelope can significantly reduce the insulation performance of the blanket. Additionally, the vacuum can be affected by changes in temperature, pressure, and other environmental factors, which can impact its effectiveness over time.

Despite these challenges, vacuum-insulated MLI blankets are widely used in spacecraft, satellites, and other applications where lightweight, compact, and highly effective insulation is required. 

Q: What is the relationship between vacuum level and heat leaks performance in MLI-type super-insulation?

A: The vacuum level in MLI-type super-insulation has a direct relationship with the amount of heat leaks. Heat leaks occur when heat energy is transferred from one area to another due to differences in temperature, and in the case of MLI-based insulation, this can occur through conduction, convection, and radiation.

When a vacuum is created between the layers of reflective material in an MLI blanket, it greatly reduces heat transfer by conduction and convection, as there are no air molecules present to carry heat energy. Therefore, the vacuum level in an MLI blanket plays a critical role in reducing heat leaks by minimizing heat transfer through conduction and convection.

However, the vacuum level also affects the insulation performance of the MLI blanket in other ways. For example, a higher vacuum level can reduce the number of air molecules present, which can minimize radiation heat transfer. The vacuum level can also impact the density of the insulation, which can affect its mechanical and thermal properties.

Generally, a higher vacuum level in an MLI blanket will result in better insulation performance, as long as the vacuum is maintained and there are no leaks or breaches in the vacuum envelope. However, achieving and maintaining a high vacuum level can be challenging, as even small leaks or breaches can significantly reduce the insulation performance of the blanket.

Therefore, careful design, manufacturing, and installation of MLI-based super-insulation is critical to ensure that the vacuum level is optimized for the specific application, and that the vacuum is maintained over the lifetime of the insulation.

Q: How does molecular sieve and hydrogen getters help to maintain vacuum over the life time of the MLI-type super-insulation?

A: Molecular sieves and hydrogen getters are two technologies that can be used to help maintain vacuum in MLI-based super-insulation over the lifetime of the insulation.

Molecular sieves are porous materials that can absorb water vapor and other gases from the environment, helping to maintain a low-pressure, low-moisture environment inside the insulation. The molecular sieve material is typically placed inside the vacuum envelope of the MLI blanket, where it can absorb any water vapor or other gases that may leak into the insulation over time. By reducing the amount of gas present inside the vacuum envelope, molecular sieves can help to maintain the vacuum level in the insulation, which can in turn improve its thermal performance.

Hydrogen getters are another technology that can be used to maintain vacuum in MLI-based super-insulation. Hydrogen getters are materials that can absorb hydrogen gas from the environment, which can be a particularly challenging gas to remove from vacuum systems. Like molecular sieves, hydrogen getters are typically placed inside the vacuum envelope of the MLI blanket, where they can absorb any hydrogen gas that may leak into the insulation over time. By reducing the amount of hydrogen gas present inside the vacuum envelope, hydrogen getters can help to maintain the vacuum level in the insulation, which can improve its overall thermal performance.

Both molecular sieves and hydrogen getters can help to maintain vacuum in MLI-based super-insulation over the lifetime of the insulation, which is critical to ensuring its long-term performance. However, it is important to note that these technologies are not a replacement for good design, manufacturing, and installation practices, which are critical to ensuring that the insulation is properly sealed and that the vacuum level is optimized for the specific application.

Q: How do hydrogen molecules infiltrate a close vacuum environment in super-insulation systems?

A: Hydrogen molecules can enter a close vacuum environment of a super-insulation in several ways, even if the insulation is well-sealed and properly designed. Here are a few potential sources of hydrogen:

1. Outgassing from materials: When materials are exposed to a vacuum environment, they can release small amounts of gas that are trapped within their structure. This is known as outgassing, and it can include hydrogen gas as well as other gases. Even materials that are specifically designed for use in vacuum environments can outgas over time, potentially leading to the presence of hydrogen in the insulation.

2. Diffusion through materials: Even if the insulation materials themselves do not contain hydrogen, the gas can still diffuse through the materials over time, particularly if there is a pressure differential between the inside and outside of the insulation. This can occur even through materials that are considered to be impermeable to gas.

3. Virtual leaks of residual gas in the vacuum envelope: Even if the vacuum envelope is designed to be completely sealed, there may still be small amounts of residual gas trapped within the insulation, especially crevices in weld joints that are under-penetrated and gaps between components in socket weld joints. This gas can include hydrogen as well as other gases, and it can slowly leak into the vacuum space over time, reducing the vacuum level and potentially impacting the insulation performance. 

4. Contamination during manufacturing or installation: Finally, hydrogen can also enter the insulation through contamination during the manufacturing or installation process. This can include small amounts of hydrogen that are introduced through the handling of materials or components, or through exposure to ambient air during installation.

In order to maintain the vacuum level and minimize the presence of hydrogen in the insulation, it is important to use high-quality materials and manufacturing processes, as well as to take steps to minimize outgassing and diffusion during installation. Additionally, technologies such as hydrogen getters can be used to help remove hydrogen from the vacuum environment over time, helping to maintain the insulation performance.

Q: How does the outgassing & virtual leak of hydrogen molecules into the vacuum annular space affect the performance of super insulation in terms of heat leaks, and why is it considered a significant challenge?

A: Hydrogen molecules are considered the biggest enemy in super insulation heat leaks performance because they have very high thermal conductivity compared to other gases, such as nitrogen or helium. This means that even small amounts of hydrogen in the vacuum annular space can significantly increase the heat transfer through the insulation system, leading to a reduction in its overall thermal performance.

Hydrogen has a higher thermal conductivity than other gases, which means it has a higher heat flux approximately four times higher than that of helium and about 10 times higher than that of nitrogen. This means that hydrogen can cause significantly higher heat leaks in vacuum insulation compared to these other gases.

In addition, hydrogen can diffuse quickly through the materials used in the insulation system, making it difficult to maintain a hydrogen-free environment over the long term. Moreover, hydrogen can also react with metals, which can lead to embrittlement or cracking of the metal parts, and affect the structural integrity of the insulation system. Therefore, the presence of hydrogen is a major concern in the design and operation of super insulation systems. 

Q: How much hydrogen typically diffuse from common cryogenic materials of construction in a typical vacuum insulated system?"

A: Carbon steel is 0.44T-L/kg (T-L = Torr-Liters), 300 series stainless steel is 0.22, Aluminum is 0.20, MLI (Glass paper and AL foil) is 5.0T-L/m3.

Disclaimer: The above data is for illustration purpose, and does not take into consideration outgassing rate & virtual leaks and/or contamination that occur during manufacturing process

Q: What is the absorption capacities of hydrogen getters and how to calculate the required quantity of hydrogen getter (Ag-X) when properly activated?

A: Generally, adsorption capacity of metal oxide such as Palladium (Pd) is 100T-L/g, Silver (Ag) is 10T-L/g.  Assuming the absorption capacity of Ag-X is 10T-L/g, vacuum insulated system mass consist of 100kg stainless steel, and MLI volume1.0 cubic meter, total hydrogen load will be = 100kg * (0.22T-L/kg) + 1.0 M3 * ( 5.0T-L/ M3) = 27 T-L.  Therefore AgX required = (27T-L) / (10T-L/g) = 2.7g

Disclaimer: The above data and calculation is for illustration purpose, and does not take into consideration outgassing rate & virtual leaks and/or the required service life of the system. 

Q: Besides hydrogen, what other molecules or gas species may potentially compromised long term vacuum integrity of MLI based insulation?

A: In addition to hydrogen, there are several other gas species that can potentially compromise the long-term vacuum integrity of MLI-based insulation. These gases can include:

1. Water vapor: Water vapor can be present in the atmosphere and can permeate through materials, including the vacuum envelope of MLI insulation. Over time, the presence of water vapor can lead to reduced vacuum levels and decreased insulation performance.

2. Oxygen: Oxygen can also be present in the atmosphere and can enter the insulation through leaks or permeation. When oxygen combines with certain materials, it can cause oxidation, leading to corrosion and potentially compromising the insulation performance.

3. Nitrogen: Nitrogen is another gas that can potentially compromise the vacuum integrity of MLI-based insulation. Like oxygen, nitrogen can enter the insulation through leaks or permeation and can cause oxidation over time.

4. Helium: Helium is a gas that is often used in leak testing and can be present in small amounts in vacuum systems. While helium itself is not harmful to MLI insulation, its presence can indicate leaks in the vacuum envelope that can lead to the presence of other, more harmful gases over time.

To minimize the presence of these gases and maintain the vacuum integrity of MLI-based insulation, it is important to use high-quality materials, design the vacuum envelope properly, and take steps to minimize outgassing and diffusion during manufacturing and installation. Additionally, technologies such as molecular sieves and other getters can be used to help remove moisture and other gases from the vacuum environment over time, improving the long-term performance of the insulation.

Q: How does the molar quantity of molecular sieve and hydrogen getters related to volume of vacuum annular space?

A: The molar quantity of molecular sieve and hydrogen getters required for a given vacuum annular space volume depends on the desired vacuum level, the outgassing rate of the materials in the system, and the required service life of the system. 

In general, the amount of molecular sieve and hydrogen getters required for a given vacuum annular space volume will increase as the required vacuum level becomes lower, the outgassing rate of the materials in the system becomes higher, and/or the required service life of the system becomes longer. However, the exact relationship between the molar quantity of molecular sieve and hydrogen getters and the vacuum annular space volume will depend on the specific system design and operating conditions.

Q: How does hydrogen getters actually work in keeping the vacuum level and heat leaks always low in a vacuum insulated system?

A: Hydrogen getters are materials that are designed to absorb hydrogen from the vacuum annular space of a super-insulated system and maintain a low level of hydrogen in the system over time. The mechanism by which hydrogen getters work is based on the adsorption of hydrogen on the surface of a metal alloy, such as palladium, at room temperature.

When the hydrogen molecules come into contact with the alloy, they dissociate into individual hydrogen atoms that then diffuse into the metal lattice and are absorbed. The hydrogen molecules continue to dissociate and diffuse until the hydrogen concentration in the vacuum annular space reaches a low level, which helps to minimize heat leaks and maintain the overall vacuum performance of the system.

Over time, the hydrogen getters can become saturated with hydrogen, which reduces their effectiveness and requires them to be replaced or regenerated. This is typically done by heating the getter material to a high temperature to desorb the hydrogen and reactivate the getter.

Q: How does metal oxide based hydrogen getters such as silver oxide removes hydrogen molecules from vacuum annular space?

A: Metal oxide based hydrogen getters, such as silver oxide, work through a process called chemisorption. The metal oxide reacts with hydrogen molecules to form metal hydrides. This process releases heat, which increases the temperature of the getter, leading to faster hydrogen adsorption. The reaction can be represented by the following equation:

Ag2O + H2 → 2Ag + H2O

The silver atoms produced in the reaction are deposited on the surface of the getter, forming a silver film. The silver film is highly reflective to infrared radiation and helps to reduce the radiative heat transfer through the vacuum annular space. Over time, the getter becomes saturated with hydrogen and needs to be replaced or regenerated to maintain its effectiveness.

Q: How to calculate the length of vacuum life expectancy based on the molar quantity of getters and molecular sieve?  

A: Yes, there are ways to estimate the length of vacuum life expectancy based on the molar quantity of getters and molecular sieve used. However, it is important to note that the actual vacuum life expectancy can be affected by various factors such as the initial vacuum level, the amount of outgassing, and the temperature of the system.

One way to estimate the vacuum life expectancy is to use the "getter capacity" concept, which is the amount of gas that a hydrogen getter can absorb before it becomes saturated. The getter capacity is typically expressed in terms of the number of liters of hydrogen gas that can be absorbed per gram of getter material. By knowing the getter capacity and the molar quantity of getters used in the system, one can estimate the amount of hydrogen that can be removed from the vacuum annular space.

Similarly, the amount of water vapor that can be removed from the vacuum annular space can be estimated based on the molar quantity of molecular sieve used and its water adsorption capacity. By knowing the amount of hydrogen and water vapor that can be removed, one can estimate the length of vacuum life expectancy before the getter and molecular sieve become saturated and need to be replaced. However, this is just an estimate and the actual vacuum life expectancy can vary depending on various factors as mentioned earlier.

Q: What is outgassing and how does it impact the heat leaks performance of super insulation system?

A: Outgassing is the process by which gases trapped within materials are released into a vacuum environment. When materials are exposed to a vacuum, any gases that are trapped within them can begin to evaporate and escape into the surrounding space. This can include gases such as water vapor, hydrogen, oxygen, nitrogen, and others.

In a super-insulation system, outgassing can impact the heat leak performance in a few ways:

1. Reduced vacuum levels: Outgassing can lead to a buildup of gas molecules in the vacuum environment, which can reduce the vacuum level and increase heat transfer. This can compromise the insulation performance over time, potentially leading to increased heat leaks.

2. Contamination: The gases released during outgassing can also contaminate the insulation materials and vacuum envelope, potentially compromising the performance of the insulation. For example, the presence of water vapor can lead to corrosion and oxidation, while the presence of oxygen can cause similar issues.

3. Reduced insulation effectiveness: If outgassing leads to a buildup of gas molecules within the insulation layers, this can also reduce the effectiveness of the insulation. This is because gases can conduct heat more effectively than solids or vacuum, leading to increased heat transfer and decreased insulation performance.

To minimize the impact of outgassing on super-insulation performance, it is important to use materials that are specifically designed for use in vacuum environments and that have low outgassing rates. Additionally, proper handling and storage of the materials prior to installation can help reduce the amount of trapped gas in the materials. Finally, the vacuum envelope must be designed to be leak-free and maintained at the appropriate vacuum level over the life of the insulation. This can help minimize the impact of outgassing on the overall insulation performance.

Q: Does MLI material outgas and how? What about molecular sieve and getters material?

A: Yes, the MLI material itself can outgas, especially during the initial stages after manufacturing and installation. This is because the MLI material is typically made of multiple layers of thin films, which can contain residual gases or solvents from the manufacturing process. These gases can be released into the vacuum environment over time, which can increase the pressure and reduce the effectiveness of the insulation.

To minimize the impact of outgassing from the MLI material, manufacturers often use specialized techniques to reduce the residual gas content in the films, such as vacuum baking or thermal cycling. Additionally, the MLI material is often designed to have a low outgassing rate by selecting materials with low vapor pressure and minimal surface area.

Molecular sieves and getters are materials that are specifically designed to absorb and remove gases from the vacuum environment. Molecular sieves are porous materials that can trap and remove water molecules and other gases, while getters are materials that react with certain gases (such as hydrogen or oxygen) to form non-volatile compounds that are trapped within the getter material.

Both molecular sieves and getters can be used in super-insulation systems to help maintain the vacuum level and prevent outgassing from the MLI material. The molecular sieve is typically incorporated into the insulation stack to help remove any residual water vapor or other gases that may be present, while the getter is often located within the vacuum envelope to absorb any gases that may enter the system over time.

Overall, the combination of a low outgassing MLI material and the use of molecular sieves and getters can help improve the long-term performance of super-insulation systems by maintaining a high vacuum level and preventing the buildup of gas molecules within the insulation layers.

Q: What are the key parameters to consider in selecting the radiation shield material for super insulated cryogenic system?

A: The selection of the radiation shield material for a super-insulated system in cryogenic applications is crucial to minimize radiative heat transfer and improve insulation performance. Some key parameters to consider when selecting the radiation shield material are:

1. Emittance: The radiation shield material should have a low emittance value, which indicates its ability to reflect or absorb radiation. Materials with low emittance values will reflect more radiation and absorb less, thus reducing radiative heat transfer.

2. Conductivity: The radiation shield material should have low thermal conductivity to reduce heat transfer by conduction. Materials with high thermal conductivity will conduct heat more efficiently and result in increased heat transfer.

3. Thickness: The thickness of the radiation shield material is important to ensure that it provides sufficient coverage to reduce radiative heat transfer. Thicker materials generally provide better insulation performance but can also add weight and cost to the system.

4. Durability: The radiation shield material should be durable and able to withstand the harsh cryogenic environment without degrading or deteriorating over time. This is particularly important in applications with long-term use or frequent thermal cycling.

5. Cost: The cost of the radiation shield material should be considered, as it can affect the overall cost of the super-insulated system. Cost-effective materials that still meet the required performance criteria should be selected whenever possible.

Q:  What are the criterias in spacer material selection for MLI ?  

A: The selection of spacer material in MLI is also an important consideration in the design of a super-insulated system. Some key parameters to consider when selecting a spacer material for MLI include:

1. Thermal conductivity: The thermal conductivity of the spacer material should be low to minimize heat transfer between adjacent layers of MLI. Materials with low thermal conductivity, such as certain types of polymer films or aerogels, are often used as spacer materials.

2. Compressive strength: The spacer material should be able to maintain the spacing between MLI layers under the compressive loads that are present during fabrication and use of the super-insulated system. The compressive strength of the spacer material should be sufficient to prevent collapse or deformation of the MLI layers.

3. Flexibility: The spacer material should be flexible enough to accommodate the differential thermal expansion and contraction that occurs between the MLI layers as the system is cooled and warmed. Rigid materials can cause stresses that may lead to failure of the MLI layers.

4. Outgassing: The spacer material should have low outgassing properties to minimize the release of gases into the vacuum space. The outgassing rate of the spacer material can be measured using techniques such as residual gas analysis (RGA) or thermal desorption spectroscopy (TDS).

5. Compatibility: The spacer material should be compatible with the other materials used in the super-insulated system. For example, the spacer material should not react chemically with the MLI layers, the vacuum space, or the cryogenic fluid.

Overall, the selection of the right spacer material for MLI is important to ensure the optimal performance of the super-insulated system.

Q: How long does the MLI material last in a typical cryogenic environment?  

A: The lifetime of MLI material in a cryogenic environment can vary depending on a number of factors such as the temperature range, the type and quality of the MLI material, and the specific application. In general, MLI material is designed to have a long service life and can last for many years in a cryogenic environment, often up to several decades. However, factors such as mechanical stresses, thermal cycling, and exposure to radiation can contribute to the degradation of the MLI material and reduce its service life. Regular maintenance and inspection can help to identify any degradation and replace the MLI material as needed to ensure continued performance of the super-insulated system.

Q: What are the factor that contribut to MLI material performance deterioration in a super insulated system?

A: The factors that can contribute to MLI material performance deterioration in a super-insulated system include:

1. Mechanical stress: Excessive mechanical stress can cause the MLI layers to shift and compress, reducing their insulation performance.

2. Radiation damage: Exposure to radiation can cause MLI materials to become brittle and degrade over time, reducing their effectiveness.

3. Outgassing: MLI materials can outgas over time, releasing gases that can condense on cold surfaces and reduce the vacuum level, leading to higher heat leaks.

4. Contamination: Contamination of the MLI layers with foreign substances, such as moisture or oils, can reduce their insulation performance.

5. Temperature cycling: Repeated cycles of thermal expansion and contraction can cause the MLI layers to shift and compress, reducing their insulation performance.

6. Aging: MLI materials can age over time, losing their insulation effectiveness and becoming less durable.

Q: How does vacuum baking or thermal cycling in VJ Pipe manufacturing process help to minimize the outgassing in a super insulated system?

A: Vacuum baking and thermal cycling are techniques used to minimize the outgassing in a super-insulated system by reducing the amount of trapped gas within the MLI material.

Vacuum baking involves subjecting the MLI material to high temperatures while under vacuum, which can cause any trapped gases or solvents to evaporate and be removed from the material. The baking process is typically carried out in a vacuum oven, which allows for precise temperature control and the removal of any gases that are released during the process.

Thermal cycling, on the other hand, involves subjecting the MLI material to a series of temperature changes between high and low temperatures. This can cause any trapped gases to expand and contract, which can help to release them from the material. The cycling process is typically carried out in a vacuum chamber, which allows for precise temperature control and the removal of any gases that are released during the process.

Both vacuum baking and thermal cycling can help to reduce the amount of trapped gas within the MLI material, which can help to minimize outgassing when the material is exposed to a vacuum environment. This can help to maintain a higher vacuum level and improve the long-term performance of the super-insulated system.

It is worth noting, however, that these techniques must be carefully controlled to prevent damage to the MLI material. For example, excessive temperatures or cycling rates can cause the layers of the material to delaminate or become damaged, which can compromise the insulation performance. Therefore, it is important to follow manufacturer guidelines and use specialized equipment to ensure that the vacuum baking or thermal cycling process is carried out correctly.

Q: How does the duration of process time during vacuum baking and thermal cycling affect the reduction of the outgassing rate of the MLI material? Furthermore, how does the length of the process time impact the useful life of the product?

A: The length of process time in vacuum baking and thermal cycling can impact the outgassing rate of the MLI material by allowing for more trapped gases to be removed from the material.

In vacuum baking, longer process times allow for more time for the material to reach a steady state and for the trapped gases or solvents to evaporate and be removed from the material. However, the process time must be carefully controlled to avoid overheating the material, which can cause damage to the insulation layers.

In thermal cycling, longer process times allow for more cycles of expansion and contraction, which can help to release trapped gases from the material. The material is typically cycled between high and low temperatures for a set number of cycles, and longer process times can allow for more cycles to be completed. However, the process time must also be carefully controlled to avoid damaging the material during the thermal cycling process.

Overall, the length of process time in vacuum baking and thermal cycling can impact the outgassing rate of the MLI material by allowing for more trapped gases to be removed from the material. However, the process time must be carefully controlled to ensure that the material is not damaged during the process, and the exact process time will depend on the specific material and insulation system being used.

The quality of a super insulated system can be classified into three major groups based on the vacuuming time and thermal cycling steps:

1. Very High Quality: This category represents the highest level of quality. The total average process time is 21 days, consisting of 2 to 4 days under rough vacuum, 4 to 6 days under medium vacuum, and 12 to 14 days under high vacuum with a turbomolecular pump. The temperature cycling ranges from 80°C to 180°C, utilizing a cryo-trap operating at -196°C (77K). Products manufactured under this level of quality typically maintain their vacuum integrity for more than 10 years.

2. Medium Quality: This category represents a moderate level of quality. The total average process time is 10 days, including 1 to 3 days under rough vacuum, 3 to 5 days under medium vacuum, and 2 to 3 days under high vacuum with a turbomolecular pump. The temperature cycling ranging from 80°C to 130°C, with a cryo-trap operating at -196°C (77K). Products manufactured under this level of quality usually maintain their vacuum integrity for a duration of 5 to 10 years.

3. Low Quality: This category represents the lowest level of quality. The total average process time is 5 days, consisting of 1 to 2 days under rough vacuum and 3 to 4 days under medium vacuum. The temperature cycling ranges from 80°C to 120°C, and a cryo-trap operating at -196°C (77K) is still utilized. Products manufactured under this level of quality generally maintain their vacuum integrity for less than 5 years.

Note: It's important to remember that these categories are based on vacuuming time, thermal cycling steps, and the longevity of vacuum integrity.

Q: How does low gassing rate preserve the vacuum performance of a super-insulated system?

A: Low gassing rate is important for preserving the vacuum performance of a super-insulated system because it helps to minimize the amount of gas that is present within the insulation layers.

If a super-insulated system contains significant amounts of gas, even if it is a high-quality vacuum, the gas can act as a thermal conductor and allow heat to pass through the insulation layers. This can compromise the insulation performance and lead to increased heat leaks.

By minimizing the amount of gas present within the insulation layers, the super-insulated system can maintain a higher vacuum level and minimize heat leaks. This is particularly important for applications where the system needs to maintain a consistent temperature or where heat transfer must be minimized, such as in cryogenic applications or spacecraft thermal control systems.

Low gassing rate can be achieved through a combination of factors, such as the use of high-quality MLI materials with low outgassing rates, careful vacuum processing techniques, and the use of molecular sieve or getter materials to remove any residual gas that may be present within the insulation layers.

Overall, low gassing rate is an important factor in preserving the vacuum performance of a super-insulated system, and careful attention must be paid to minimize gas levels and maintain the integrity of the insulation layers over the lifetime of the system.

Q: How does layer density of MLI influence the performance of super-insulation?

A: The layer density of Multi-Layer Insulation (MLI) can have a significant impact on the performance of a super-insulation system. Layer density refers to the number of insulation layers per unit area, and it can affect the thermal conductivity, flexibility, and overall effectiveness of the insulation.

In general, increasing the layer density of MLI can improve its thermal insulation properties. This is because additional insulation layers reduce the number of direct heat transfer paths between the outer surface and the inner vacuum space, which reduces heat transfer via conduction and radiation. However, increasing layer density can also increase the stiffness and weight of the insulation, which can be problematic in some applications.

The optimal layer density for a given super-insulation system will depend on a number of factors, including the specific materials used, the size and shape of the insulation, and the desired performance characteristics. In some cases, a lower layer density may be sufficient to meet the required insulation performance while maintaining flexibility and weight.

It is worth noting that increasing the layer density of MLI may not always result in a linear improvement in insulation performance. As the layer density increases, the insulation layers become increasingly compressed, which can reduce their effectiveness at blocking heat transfer. Additionally, increasing the layer density can increase the likelihood of inter-layer contact and thermal bridging, which can compromise the insulation performance.

Overall, the layer density of MLI is an important consideration in the design and performance of a super-insulation system, and careful attention must be paid to balancing insulation performance with other factors such as weight, flexibility, and durability.

Q: What is the heat leaks performance comparing MLI to Aerogel in a super-insulation system under similar cryogenic condition?

A: Both Multi-Layer Insulation (MLI) and Aerogel are highly effective super-insulation materials, but their relative performance in cryogenic applications can depend on a variety of factors.

In general, MLI is more commonly used for cryogenic insulation than Aerogel, particularly in applications where a very low heat leak rate is required. MLI has a very low thermal conductivity and can provide high-performance insulation even at cryogenic temperatures.

Aerogel, on the other hand, has a higher thermal conductivity than MLI, but it also has a lower density and is a better insulator against convection. In some cases, Aerogel may be used in combination with MLI to provide additional insulation and minimize heat transfer via convection.

Ultimately, the choice between MLI and Aerogel will depend on the specific requirements of the application, such as the desired level of insulation, the temperature range, and the available space and weight constraints. In some cases, a combination of both MLI and Aerogel may be used to achieve the optimal insulation performance.

Q: If condensation appear on the outer pipe surface of a vacuum jacketed system, what does this indicates?

A: If condensation appears on the external surface of the jacket pipe in a Multi-Layer Insulation (MLI) based super-insulated coaxial pipe, it may indicate that the insulation performance of the system has been compromised. 

The presence of condensation suggests that the external surface of the jacket pipe is colder than the dew point of the surrounding air, causing water vapor to condense on the surface. This could be an indication that the insulation system is not providing adequate insulation, allowing heat to transfer from the inner pipe to the outer jacket pipe and cooling the external surface below the dew point.

Possible reasons for this could include:

1. Poor vacuum insulation: If the vacuum insulation system is not functioning correctly or has been damaged, it may not be providing sufficient insulation to prevent heat transfer and keep the external surface of the jacket pipe warm.

2. Outgassing: Outgassing from the MLI layers or other materials within the insulation space can release moisture into the vacuum space.

3. Leaks: If there are any leaks in the vacuum insulation system, air and moisture can enter the insulation space and compromise the vacuum.

4. Environmental conditions: If the surrounding air temperature and humidity are high, it can cause moisture to accumulate on the external surface of the jacket pipe and eventually lead to condensation.

5. Improper installation: If the vacuum insulation system is not installed correctly, gaps or spaces may be left within the insulation space that allow air and moisture to enter.

6. Inadequate MLI layers: If there are not enough layers of MLI in the insulation system, or if the MLI layers are not spaced correctly, they may not be providing enough insulation to prevent heat transfer.

7. Thermal bridging: If there are any thermal bridges between the inner pipe and the outer jacket pipe, they may be allowing heat to transfer from the inner pipe to the jacket pipe, reducing the effectiveness of the insulation.

In any case, the presence of condensation on the external surface of the jacket pipe is a clear indication that the insulation system may not be performing as expected and further investigation may be required to identify and rectify the problem.

Q: Is outgassing one of major contributing factor for above phenomenal?

A: Yes, outgassing can be a contributing factor to the formation of condensation on the external surface of the jacket pipe in a Multi-Layer Insulation (MLI) based super-insulated coaxial pipe. Outgassing is the release of trapped gases from materials used in the insulation system, and these gases can condense on colder surfaces if the vacuum insulation system is not functioning properly. This can result in a build-up of ice or frost on the external surface of the jacket pipe, which can eventually melt and form condensation. Therefore, minimizing outgassing by using suitable materials and proper vacuum baking procedures is important to maintain the performance of the insulation system and prevent the formation of condensation.

Q: When vacuum level degrade, how does it impacts the MLI radiation shield capacity and performance?  

A: When the vacuum level in an MLI-based super-insulated system degrades, it can significantly impact the performance of the radiation shield. The MLI radiation shield is designed to reflect and dissipate heat through a series of reflective and conductive layers. When the vacuum level degrades, the effectiveness of the reflective layers is reduced as there is more air molecules in the space, which can absorb heat and contribute to thermal conduction. This increases the heat transfer through the shield, reducing its thermal performance. As a result, it is important to maintain a high vacuum level to ensure the long-term performance of the MLI-based super-insulated system.

Q: What happen to MLI radiation shield capacity when the vacuum level drop below 10E-3mBar? 

A: When the vacuum level drops below 10E-3 mBar, the MLI radiation shield's capability to reflect and block radiation decreases significantly. This is because the reduced vacuum level allows for more gas molecules to be present in the vacuum annular space, which increases conduction and convection heat transfer. This, in turn, leads to higher heat leak rates and reduces the overall performance of the super-insulated system. Therefore, it is important to maintain a high vacuum level in MLI-based super-insulated systems to achieve optimal performance.

Q: What is the minimum desired vacuum level for MLI to perform to its best efficiency?  

A: The minimum desired vacuum level for Multi-Layer Insulation (MLI) to perform efficiently depends on the specific application and operating conditions. However, typically a vacuum level of 10^-4 to 10^-5 torr or better is desirable for MLI-based insulation systems. Maintaining a low vacuum level is essential to minimize heat transfer through conduction, convection, and radiation. As the vacuum level increases, the mean free path of the gas molecules increases, leading to a decrease in thermal conductivity. Therefore, maintaining a low vacuum level is critical to achieving high levels of thermal insulation performance.

Q: Does good quality super insulated pipe able to last more than 10 years in useful life?

A: Yes, a well-designed and well-constructed super-insulated pipe should be able to last more than 10 years of useful life. However, the actual lifespan of the pipe will depend on a number of factors, including the specific cryogenic application, the quality of materials and construction, the maintenance and inspection schedule, and the operating conditions. Regular maintenance and inspection can help to identify and address any potential issues before they become more serious and impact the overall performance and lifespan of the system.

Q: How does good manufacturing practice such as good quality welding techniques and helium leak testing help in preserving the life expectancy of super-insulated system?

A: Good manufacturing practices, such as good quality welding techniques and helium leak testing, are important in preserving the life expectancy of super-insulated systems by ensuring the integrity of the insulation system. 

In the case of welding, high-quality welds can prevent air or moisture from entering the system, which can compromise the vacuum insulation and lead to heat leaks. Proper welding techniques, such as ensuring proper fit-up and using suitable welding parameters, can help ensure high-quality welds that maintain the integrity of the insulation system.

Helium leak testing is another important practice that can help detect and locate leaks in the insulation system. Helium is a small molecule that can easily penetrate small gaps or holes in the insulation system, and by introducing helium into the system and measuring its concentration outside the system, leaks can be detected and located. This allows for prompt repair of any leaks before they can compromise the vacuum insulation and lead to heat leaks.

In summary, good manufacturing practices such as good quality welding techniques and helium leak testing are important in preserving the life expectancy of super-insulated systems by ensuring the integrity of the insulation system and preventing heat leaks.

Q: Is orbital welding well accepted as best fabrication practice in manufacturing of coaxial super insulated pipe?

A: Yes, orbital welding is often considered as the best fabrication practice in manufacturing of coaxial super-insulated pipe. 

Orbital welding is a high-quality welding technique that uses a computer-controlled welding head to produce consistent and precise welds. This technique is particularly suited for welding of thin-wall pipes, such as those used in super-insulated systems, where precision and quality are important to ensure the integrity of the insulation system.

Orbital welding has several advantages over traditional welding techniques, including reduced risk of contamination, improved repeatability, and increased efficiency. It can also produce high-quality welds that meet the stringent requirements of super-insulated systems, such as high vacuum and low outgassing rates.

Overall, orbital welding is a well-accepted practice in the manufacturing of coaxial super-insulated pipes, and it is often used to ensure the quality and integrity of the insulation system.

Q: What is the performance advantage if a super-insulated system is helium leak tested to lesser than 1 x 10E-9cc/s.atm compared to being tested at 1 x 10E-7cc/s.atm 

A: The performance advantage of a super-insulated system that is helium leak tested to a lower value, such as lower than 1 x 10E-9 cc/s.atm, compared to a system that is tested to a higher value, such as lower than 1 x 10E-7 cc/s.atm, is related to the system's ability to maintain its vacuum level over time.

Helium leak testing is a critical step in the fabrication of super-insulated systems to ensure that the insulation system has no leaks that could compromise its performance. The lower the leak rate, the better the vacuum performance of the insulation system, and the longer it can maintain its vacuum level over time.

A system that is helium leak tested to a lower value, such as lower than 1 x 10E-9 cc/s.atm, is likely to have a better vacuum performance than a system that is tested to a higher value, such as lower than 1 x 10E-7 cc/s.atm. This is because the lower leak rate means that there are fewer leaks in the system, and hence, the system can maintain its vacuum level more effectively.

In general, a lower helium leak rate indicates a better vacuum integrity of the system, which leads to lower heat leaks and better insulation performance. Therefore, a system helium leak tested to lower than 1 x 10E-9cc/s.atm would be expected to have a longer life expectancy than a system helium leak tested to lower than 1 x 10E-7cc/s.atm, assuming all other factors are the same.

In summary, the performance advantage of a super-insulated system that is helium leak tested to a lower value is a better vacuum performance, which results in improved insulation performance and longer life expectancy of the system.

Q: Is CFOS process more superior in stainless steel components cleaning in manufacturing of super-insulated system?

A: Clean for oxygen service "CFOS" refers to a stringent cleaning process required for components or systems that come into contact with oxygen in various applications, such as medical devices, aerospace, or industrial settings. The cleaning process aims to eliminate any contaminants that could react with oxygen and potentially pose a safety risk. It involves thorough cleaning, often using specialized solvents, detergents, or ultrasonic baths. Validation of cleanliness typically involves various tests, such as visual inspection (black-light & water break), cleanliness analysis, and chemical residue analysis, ensuring the components or systems meet the necessary criteria for safe and reliable oxygen use.

While CFOS cleaning process is effective at removing contaminants from metal surfaces, it may not necessarily be considered a superior technique for all stainless steel components used in the construction of super-insulated systems. The choice of cleaning process depends on the specific application and the type of contaminants present on the surface. Other cleaning techniques such as ultrasonic cleaning, acid pickling, and electropolishing may also be suitable for certain applications. CSM has developed our in-house cleaning process to ensure it meets not just for CFOS, but low outgassing in high vacuum application.

In general, the selection of cleaning process are based on factors such as the type and level of contaminants present, the materials and components being cleaned, and the desired surface finish. Additionally, CSM follow good manufacturing practices and quality control procedures to ensure that the cleaning process does not introduce any new contaminants or damage the components. 

CSM CFOS process comply to several standards below:

1. ASTM G93: This standard provides guidelines for cleaning methods and procedures for components used in oxygen-enriched environments.

2. ISO 15001: ISO 15001 sets requirements for cleaning procedures and acceptance criteria for components and systems that come into contact with oxygen.

3. CGA G-4.1: The Compressed Gas Association (CGA) publication G-4.1 outlines guidelines for cleaning compressed gas equipment, including equipment used with oxygen.

4. NASA-STD-6001: NASA's standard covers the cleaning, packaging, and testing requirements for oxygen components used in space systems.

5. ASTM E491: This standard provides a guide for cleaning methods and protocols for removing organic and inorganic contaminants from surfaces used in UHV systems.

6. ISO 14919: ISO 14919 outlines procedures and requirements for the cleaning of surfaces in UHV environments, including guidelines for ultrasonic cleaning, solvent cleaning, and surface analysis techniques.

7. SEMI F19: SEMI F19 is a standard developed by SEMI (Semiconductor Equipment and Materials International) for cleaning surfaces and components used in the semiconductor industry, including those in UHV systems.

Q: How effective is CFOS cleaning process to improve heat leak performance and life expectancy of vacuum insulated system?

A: CSM proprietary CFOS cleaning process is used to improve the surface cleanliness of stainless steel components used in vacuum insulated systems by removing lubricants, oil, grease and trace hydrocarbon. Our process has been shown to be effective in improving the heat leak performance and life expectancy of vacuum insulated systems, by preventing surface outgassing that reduces the vacuum quality of the system.

Overall, CFOS can be a useful tool in the manufacturing of vacuum insulated systems. However, it is important to note that CFOS is just one part of a comprehensive manufacturing and quality control process for vacuum insulated systems, and other factors such as welding quality and vacuum sealing techniques also play important roles in the overall performance and life expectancy of the system.

Q: Does clean room environment and clean work practice important in manufacturing of high performance super-insulated vacuum system?

A: Yes, maintaining a cleanroom environment and following clean work practices is very important in producing high-performance super-insulated vacuum systems. This is because contaminants such as dust, oils, and other particles can significantly reduce the vacuum performance of the insulation. In particular, they can increase the outgassing rate of the MLI and other materials used in the system, leading to higher heat leaks and reduced insulation effectiveness.

To minimize these issues, manufacturers of super-insulated vacuum systems typically use cleanrooms to assemble and test their products. They also follow strict procedures for cleaning and handling components and materials to prevent contamination. For example, components may be cleaned using solvents or other cleaning agents, and then placed in sealed containers to prevent re-contamination before assembly.

Overall, maintaining a clean and controlled environment throughout the manufacturing process is critical for achieving high-performance super-insulated vacuum systems with long lifetimes.

Q: What are the general miss-conceptions about MLI based super-insulation and vacuum insulation?

A: There are several misconceptions about MLI based super-insulation and vacuum insulation, including:

1. Vacuum lasts forever: Although vacuum is an excellent insulator, it is not perfect and will eventually degrade over time. Molecules will slowly leak into the vacuum space; outgassing is causing a gradual increase in heat transfer. Therefore, vacuum insulation systems require periodic maintenance to maintain their performance, although good quality vacuum insulated pipe will last 10 years without the need for vacuum maintenance. 

2. MLI is indestructible: MLI is a fragile material and can be easily damaged during handling or installation. Even small tears or punctures can significantly reduce its insulating performance. Proper care must be taken to ensure that MLI is handled and installed correctly to maintain its integrity.

3. All types of MLI are the same: There are many type of MLI material with varying quality and prices available. While MLI is a highly effective insulation material, it may not be suitable for some cryogenic applications. Factors such as the operating temperature, vacuum level, and mechanical stress need to be considered. 

4. Vacuum insulation is always the best choice: While vacuum insulation can offer excellent thermal performance, it may not always be the most cost-effective solution. In some cases, the cost of maintaining a vacuum may outweigh the benefits especially low quality vacuum jackted pipe. 

5. MLI can provide unlimited insulation performance: MLI's insulating performance is limited by the number of layers used. Adding more layers will improve performance up to a point, but beyond a certain point, the benefits of additional layers diminish. The optimal number of layers will depend on the specific application and operating conditions.

Q: For liquid nitrogen application, is coaxial super-insulated pipe bring higher ROI than PU foam-insulated pipe?  

A: The ROI (Return on Investment) of using coaxial super-insulated pipe versus PU foam-insulated pipe for liquid nitrogen application depends on various factors such as the cost of materials, installation, and maintenance, the operating conditions, and the required performance. 

In general, coaxial super-insulated pipe provides higher thermal performance and lower heat leak compared to PU foam-insulated pipe, which can result in reduced liquid nitrogen consumption and cost savings over time. However, coaxial super-insulated pipe may have a higher initial cost due to the complexity of its design and fabrication process. 

Therefore, the choice between the two types of insulation depends on the specific requirements and budget of the application. A thorough cost-benefit analysis should be conducted to determine the most suitable option for a given application.

Q: What is the typical heat leaks deterioration profile of a vacuum insulated pipe?

A: The heat leak rate in a vacuum insulated pipe can deteriorate over time due to various factors such as vacuum loss, radiation shield degradation, and insulation material settling. The exact profile of heat leak deterioration can vary depending on the specific factors involved and the operating conditions of the pipe.

In general, the heat leak rate tends to increase gradually over time due to vacuum loss and radiation shield degradation, which can be accelerated by factors such as vibration, thermal cycling, and exposure to contaminants. The insulation material may also settle or compact over time, which can lead to increased heat leaks.

It is important to regularly monitor the heat leak rate of vacuum insulated pipes to detect any deterioration and take appropriate measures to maintain the performance of the system. This may involve recharging the vacuum, replacing damaged or degraded insulation or radiation shields, and ensuring that the system is properly maintained and operated.

Q: Generally speaking, does it make economic sense to use vacuum insulated pipe to transfer liquid nitrogen from a storage tank to point-of-use in a distance away, example 50 meters?

A: In general, using vacuum insulated pipe to transfer liquid nitrogen over a distance of 50 meters or longer can be economically viable, depending on several factors such as the cost of the pipe, installation, maintenance, and the cost of the liquid nitrogen being transferred. 

Vacuum insulated pipes are more expensive than traditional insulated pipes, but they have higher thermal efficiency and lower heat losses. Therefore, the economic feasibility of using vacuum insulated pipes depends on the volume of liquid nitrogen being transferred, the distance to be covered, and the cost of the liquid nitrogen. 

For longer distances and larger volumes of liquid nitrogen, the reduced heat losses of a vacuum insulated pipe can lead to significant cost savings in terms of the amount of liquid nitrogen needed to be produced and the energy required to maintain the desired temperature. However, for shorter distances and smaller volumes of liquid nitrogen, the cost of the vacuum insulated pipe and installation may outweigh the potential savings from reduced heat losses. 

In summary, the economic viability of using vacuum insulated pipe to transfer liquid nitrogen over a distance of 50 meters or longer depends on several factors, including the cost of the pipe and installation, the volume of liquid nitrogen being transferred, and the cost of the liquid nitrogen.

Q: How does excessive heat leak compromised the effective transfer of liquid nitrogen in a vacuum jacketed pipe line?

A:Excessive heat leak in a vacuum insulated pipe can cause the temperature of the cryogenic liquid, such as liquid nitrogen, to rise above its boiling point, resulting in vaporization of the liquid. The vaporization of liquid nitrogen can cause an increase in pressure inside the pipe, which can lead to the pipe becoming pressurized and the cryogenic liquid not being able to flow effectively to its destination. Additionally, excessive heat leak can cause the cryogenic liquid to partially or fully evaporate, leading to a loss of product and potentially dangerous situations if the vaporized gas is not handled properly. Therefore, it is important to minimize heat leak in vacuum insulated pipe to ensure efficient and safe transfer of cryogenic liquids.

Q: What is the typical heat leaks value between vacuum insulated pipe compared to PU foam insulated pipe?  

A: The heat leak value for vacuum insulated pipes (VIPs) varies depending on several factors, including the design, insulation thickness, and the quality of the vacuum. Generally, VIPs have a much lower heat leak value compared to PU foam insulated pipes due to the superior insulation properties of vacuum. The heat leak value for VIPs can be as low as 0.1 W/m or even lower, while for PU foam insulated pipes, it can range from 5 to 15 W/m.

Q: How is the heat leaks performance of vacuum jacketed pipe deteriorate against time compared to PU foam insulated pipe?  

A:  The heat leak performance deterioration of PU foam insulated pipe and vacuum insulated pipe can be compared based on the time-dependent heat ingress rate (HIR) values. 

For PU foam insulated pipes, the HIR values generally increase over time due to the gradual degradation of the insulation material, as well as the formation of voids and cracks within the foam. This can lead to an increased thermal conductivity and, hence, higher heat leaks.

On the other hand, for vacuum insulated pipes, the HIR values tend to remain relatively stable over time as long as the vacuum integrity is maintained. However, if there is a loss of vacuum due to factors such as permeation, outgassing or leakage, then the HIR values can increase significantly, leading to compromised insulation performance.

In general, vacuum insulated pipes are designed to have a much lower heat leak performance and a longer service life compared to PU foam insulated pipes, especially for applications involving the transfer of cryogenic liquids such as liquid nitrogen.

Q: What are the major disadvantages of PU foam insulated pipe compared to vacuum insulated pipe in liquid nitrogen application?

A: There are several disadvantages of PU foam insulated pipe compared to vacuum insulated pipe in liquid nitrogen application, including:

1. Higher heat leaks: PU foam insulation has higher thermal conductivity compared to vacuum insulation, which leads to higher heat leaks and greater loss of cryogen.
2. Larger pipe diameter: In order to achieve the same level of heat leak as vacuum insulated pipe, PU foam insulated pipe requires a larger pipe diameter, which can lead to higher installation costs and space constraints.
3. Limited useful life: PU foam insulation has a limited useful life and requires periodic maintenance and replacement, which can add to operational costs.
4. Environmental concerns: PU foam insulation contains chemicals that are harmful to the environment and require proper disposal, which can add to disposal costs and pose potential environmental risks. 
5. Lower thermal efficiency: PU foam insulation has lower thermal efficiency compared to vacuum insulation, which means it may not be suitable for applications where high thermal efficiency is critical.

Overall, vacuum insulated pipe is typically considered to be the preferred choice for cryogenic applications due to its superior thermal performance and longer useful life.

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