Today, technical gases are required in large quantities for countless processes. Depending on the type of gas, it may be necessary to store the gas in liquid form, usually in cryogenic temperature ranges. For example, classic industrial gases such as nitrogen are kept at a constantly low temperature level in large insulated containers to keep them liquified and thereby be able to store much higher quantities per volume. Here a high degree of tightness of the insulated container is essential.
- High leak tightness
- Long post - evacuation intervals
- Good end pressure
How does it work?
In order to avoid a pressure increase due to temperature rise, insulated containers must be thermally insulated in the best possible way. The insulation effect is achieved by a multi-walled structure of insulation containers, whereby the liquified gas is stored in the central volume of the insulation container and is covered by an insulation layer.
The insulation effect is achieved by means of a vacuum in the 10-8 mbar range or by a perlite filling in combination with evacuation in the fine vacuum range. The important factor is the mean free path length of the molecules in the insulation layer, which is decisive for the heat transfer. The mean free path length indicates the contact frequency of the molecules with the wall or the molecules with each other. Due to the porous structure of the perlite, molecules are trapped within material and thus the heat transfer is considerably reduced. With high tightness requirements for the insulation container, post-evacuation intervals of 10 years are aimed for.
Pfeiffer Vacuum offers a broad portfolio of products for evacuating both the gas volume and the insulation layer. Depending on the vacuum required, Pfeiffer Vacuum can supply the best suited pump technology which might be a roots pumping stations, but can also be dry backing pump or rotary vane pump in combination with turbopumps. In addition to that, Pfeiffer Vacuum also offers gas analysis solutions, measurement gauges, components, valves and also leak detectors for the final test of the insulation.