Industrial Hot/Cold Transfer Pipe – Vacuum Insulated Pipe

Quest has successfully developed Wrapped Multi-Layer Insulation (WMLI), a promising innovative, next generation cryogenic pipe insulation specifically engineered to insulate cryogenic feedlines or industrial cold transfer lines such as Vacuum Jacketed Pipe. WMLI development included designing, modeling, analyzing, fabricating prototypes, installing them on cryogenic piping and measuring thermal performance. WMLI uses Quest’s proprietary Discrete Spacer Technology, with a new spacer designed, analyzed and tested on various geometry tubing installations. About 15 different micromolded polymer spacers were considered, as well as novel “post-on-demand” spacers utilizing a new on the fly manufacturing process, with a final custom Triple Orthogonal Disk (TOD) spherical polymer spacer selected, tested, and proven to provide very high thermal performance. Novel nested shell components made with rapid prototyping techniques were designed and tested, and will allow rapid insulation of complex tubing. WMLI offered superior performance to traditional MLI installed on cryogenic pipe, with 2.2W/m2 heat flux compared to 5.5W/m2 for advanced clamshell netting MLI and 26.6W/m2 for traditional spiral wrapped MLI. WMLI as inner insulation in Vacuum Jacketed Pipe can offer heat leaks as low as 0.09 W/m, compared to industry standard VJP with 0.31W/m.

A major part of this program was the design and development of a discrete spacer customized for WMLI use on pipe. The TOD spherical spacer was thoroughly modeled and analyzed, then tooled and micromolded, and used to build WMLI prototypes.  Boiloff calorimetry gave the best measured thermal performances achieved – as low as 2.22W/m2 for a 5-layer pipe insulation. This result compares to our prior Phase I prototype heat flux of 7.3W/m2, showing great improvement in WMLI insulation performance during this Phase II program.

A new WMLI fabrication/installation process was designed and implemented using a “clamshell” installation approach as opposed to the previous helical wrap, and provides faster installation as well as superior performance. A new wrapped insulation concept was also designed and tested for corners, bends and conflats, and was another aspect in achieving a low heat flux.

New SLA rapid prototype pre-formed corner shells were designed and shown to be a practical approach to rapid installation on complex cryogenic tubing such as T’s, 4-way valves or flanges. SLA shell components offered reasonable thermal performance.

Advanced modeling of the TOD spacer was done in Thermal Desktop and exported into Thermal Analysis Kit for further analysis. The ability to model and predict WMLI performance is useful in designing WMLI insulation systems, as well as provides insight into total system heat leak. Modeled thermal results now match measured results reasonably well, and predictability of WMLI performance is greater than for conventional MLI insulation. Traditional MLI on cryo piping shows “degradation” factors of 6 to 20 over heat leak predicted by the Lockheed equation; WMLI currently uses a semi-empirical “correction” factor of 0.57 against our custom TD/TAK model, and as the model is improved predictive ability will improve.

The WMLI Phase II program achieved significant improvements in WMLI performance, accomplished all program technical objectives, and demonstrated that WMLI is a superior, next generation cryogenic pipe or vacuum jacketed pipe insulation, with up to 12-fold lower heat flux than current insulation.

Detailed Summary

• Extensive design and modeling work was done on a discrete spacer for wrapped pipe insulation. From a dozen concepts, three were selected to prototype using stereolithography and building mockups.
• A concept for fabricating spacers (posts) on demand was investigated, and while deemed possible and having good potential, required more time and effort than possible in this program. Post-on-demand would create a spacer post using a microsphere-polymer slurry that could be dispensed and formed as needed.
• Using Quest’s Discrete Spacer Technology, the spacer was designed around principles that reduce the effective area/length, minimizing solid heat conductance.  The final design uses a Triple Orthogonal Disk (TOD) spherical spacer, that touches adjacent dual aluminized mylar layers on the edges of 0.010” thick disks, providing for a very small contact area and a low effective A/L ratio of 0.00011 inches.
• WMLI prototypes using the TOD spacer, and new techniques developed for wrapping/installing insulation on both straight sections and over complex tubing geometries (such as corners, bends, T’s, valves, conflats), had a heat leak as low as 2.22W/m2.
• Another new concept developed was using rapid prototype SLA nested shell pieces to cover complex components such as corners and T’s. Again, designs minimized A/L and emissivity, and prototype parts were fabricated, installed, tested, and shown to provide reasonable performance (not quite as good as the full TOD wrapped system) with very rapid installation.
• WMLI moved from an initial helically wrapped pipe insulation to a straight, clamshell wrapped system for better performance (fewer spacers per unit area needed), lower cost, and faster installation.
• WMLI modeling was moved to the next level, with the TOD analyzed in Thermal Desktop, then exported into Thermal Analysis Kit, allowing reasonably accurate heat leak predictions. These proprietary thermal models allow us to design a WMLI system for specific requirements, and also provide useful insight into what factors affect total system heat leak, guiding system improvements.
• Heat conduction through the TOD spacer, as well as the bonded and unbonded interfaces to adjacent mylar layers, was modeled and compared to actual measured values, and is now better understood.
• 13 prototype build/test cycles were iterated, leading to improvement in WMLI performance from 7.2W/m2 to 2.22W/m2 (5 layers, 77K to 295K).
• A Ground Support Equipment testbed was designed and built to test WMLI as the inner insulation in Vacuum Insulated/Vacuum Jacketed Pipe, and WMLI was installed on this 10’ long 1.5” diameter VJP. WMLI/VJP performance was good (2.52W/m2).
• WMLI performance compared to traditional netting-based MLI:
  • WMLI                                     2.2 W/m2
  • Advanced clamshell MLI   5.5 W/m2
  • Spiral wrapped MLI            26.6 W/m2
• WMLI/VJP performance compared to industry standard state-of-the-art VJP:
  • 0.5” diameter pipe      WMLI/VJP is 0.09 W/m, Standard VJP is 0.31 W/m
  • 0.75” diameter pipe   WMLI/VJP is 0.19 W/m, Standard VJP is 0.37 W/m
  • 1.5” diameter pipe     WMLI/VJP is 0.30 W/m, Standard VJP is 0.54 W/m
• WMLI offers a robust, repeatable insulation, with higher performance than conventional MLI on cryogenic feedlines
• WMLI is a high performance, next generation pipe insulation system, with applications for spacecraft cryogenic piping and terrestrial industrial cold/hot transfer piping

The next Phase for WMLI development is to select one or more vendors of industrial hot/cold transfer piping (typically this would be high performance Vacuum Jacket Pipe) to customize WMLI for their product, fabricated test samples and do further testing to confirm the performance advantage of WMLI over other traditional VJP inner insulations.  This should lead to a premium performance VJP product.

Potential Terrestrial/Industrial Applications

Extremely efficient thermal insulation, easily assembled and applied to cover various surfaces, including pipes and tubing, have utility in commercial cryogenic applications such as cryogenic vessels and lines in scientific and industrial applications. Insulated cryogenic tubing is used for transfers of cryogenic liquid into and from cryogenic dewars for liquid nitrogen (LN2), liquid helium, liquid oxygen and liquid natural gas, which are widely used in research, medical and industrial applications.

The parent IMLI technology can be used to insulate cryogenic dewars and cryotanks.  Other potential applications include large commercial tanks, industrial boilers and industrial hot and cold process equipment, refrigerated trucks and trailers, insulated tank, container and rail cars, liquid hydrogen fueled aircraft or fuel cells, appliances such as refrigerators and freezers.

There are several major industrial uses for cryogenic lines and handling equipment. Cryogenic pipes, lines and tubing uses include LN2 handling products such as flexible cryogenic hoses, bendable LN2 piping, rigid piping, a variety of automatic filling equipment, dewar manifolds and gas panels. LN2 equipment is used for industrial or food applications including semiconductor, electronics and aerospace environmental temperature testing, special effects (fogging), biological freezing applications, inerting of food and beverage containers, container pressurization and food freezing.

Liquid Nitrogen has numerous uses for food and beverage preservation (“inerting”).  Injection applications include full container inerting, headspace inerting, and pressurization of cans and PET bottles. LN2 inerting is commonly used for peanuts, trail mix, wine, dog food, potatoes, cheese, peanut butter, yogurt, beer, malted beverages and oils.  LN2 pressurization also finds many applications, such as pressurizing water, corn syrup, bar mixes, apple juice, oil, energy drinks and teas.

High performance insulated cryogenic transfer piping is critical to the LNG industry, where heat gain into pipes causes LNG losses from vaporization during transportation from offshore wellheads to the LNG terminal. Traditional methods of field fabrication and insulation of LNG transfer piping leave great opportunities for improvement. Current foam insulated pipe is inherently a poorer insulator than aerogel or Vacuum Insulated Pipe, with much less thermal insulation than WMLI is expected to provide, and due to insulation break down requires frequent and expensive maintenance.

Cryogenic piping is used to transfer cryogens to and from dewars in dewar manifolds, in LN2 delivery systems, LN2 tool connections, and OEM applications.  State of the art high performance cryogenic liquid handling and transfer lines are currently manufactured from vacuum insulated pipe (VIP). VIP is typically made from stainless steel flexible or bellowed tubing, filled with Multi-Layer Insulation, may have getters added, then pumped down to high vacuum and sealed.  VIP generally uses conventional MLI technology to insulate cryogenic tubing.  Known problems with conventional MLI technology for tubing use include layer density control (layer spacing increases above that for best performance), inter-layer contact increases during wrapping increasing thermal conductivity, typical wrapping schemes have a mismatch of temperature layers (cold layers contact hotter layers), seam sealing, and insulation of bends and elbows.  Lower performance cryogenic lines are typically made from polyurethane foam insulated plastic piping.

There is a substantial market for Vacuum Insulated Pipe, which is a product that the new WMLI technology could offer improved performance.  Foam insulated piping has heat leaks as high as 7.3 W/m, and current Vacuum Insulated Pipe has heat leaks of 0.5 – 1 W/m, while WMLI on 0.5” diameter pipe has a heat flux of 0.3W/m.