If a cryobank is the heart of a research facility, then the vacuum-insulated pipes are its veins. They transport the liquid nitrogen from the external bulk tank through the building to the individual storage tanks - silently, invisibly and around the clock.
The quality of these lines has a direct and measurable impact on the efficiency and reliability of your entire cryogenic infrastructure. A poorly insulated line loses nitrogen on the way to the tank, generates unwanted gas and drives up operating costs. A high-quality vacuum-insulated line, on the other hand, delivers the nitrogen to the tank almost as cold as it left the bulk tank.
In this article, we explain the technology behind vacuum-insulated pipes, their importance for overall operation and the factors that need to be taken into account during planning.
A vacuum-insulated pipe consists of two concentric pipes: the inner process pipe, which carries the liquid nitrogen, and the outer jacket pipe, which encloses the vacuum space. There is a high vacuum between the two pipes, which virtually eliminates heat input through convection and conduction.
The vacuum chamber contains several layers of a special insulating film (multilayer insulation, MLI). These foils reflect the heat radiation and thus reduce the only remaining heat transfer mechanism: radiation. The result is an insulation performance that is orders of magnitude better than any foam insulation.
At cryogenic temperatures, the inner pipe shrinks due to thermal contraction. Expansion joints (bellows) in the inner pipe absorb this change in length and thus prevent mechanical stresses that could lead to leaks.
In a non-vacuum-insulated line - such as a foam-insulated stainless steel line - the evaporation loss over long distances can amount to 30-50% of the transported nitrogen. In a high-quality vacuum-insulated line, this loss is typically less than 5%. The savings over the years add up to considerable amounts.
High evaporation losses not only mean economic losses - they also generate a high proportion of gas (two-phase mixture) in the nitrogen flow. This gas content can disrupt the filling of the tanks and requires additional treatment, as described in our article on phase separators.
Poorly insulated cables can form condensation or even ice on their outer surface. In a laboratory environment, this is not only an aesthetic problem, but also a potential safety risk due to the risk of slipping and moisture entering electrical systems.
Planning the cable route requires close coordination with architects and building services engineers. Among other things, openings through walls and ceilings, the avoidance of heat sources near the pipe, accessibility for maintenance work and compliance with minimum bending radii must be taken into account.
The diameter of the line must be designed for the maximum nitrogen flow rate. Pipes that are too small generate high flow velocities and pressure losses, while pipes that are too large are uneconomical and require more space.
Vacuum-insulated valves and distributors are installed at strategic points to distribute the nitrogen flow to different consumers and isolate individual sections as required.
Vacuum-insulated lines are generally low-maintenance systems. Regular inspection includes checking for external damage, checking the vacuum indicator (if present) and inspecting the expansion joints and valves. The service life of a high-quality line is several decades.
Consarctic® designs and installs complete liquid nitrogen supply systems including all vacuum insulated piping, phase separators, manifolds and valves. Our solutions are tailor-made: from a short connection between a bulk tank and a single cryogenic room to complex networks supplying multiple building wings and floors.
Do you need an automatic LN2 supply for your facility? Our planning engineers will work with you to develop the optimum solution for your spatial and logistical requirements.