Liquid CO₂ storage tank · Insulation type (polyurethane, polystyrene, vacuum-perlite), design pressure and temperature, design code, level and relief equipment, connections
A liquid CO₂ storage tank holds refrigerated liquid carbon dioxide under pressure on site, buffering between deliveries or CO₂ recovery and the points of use. Ask three things first: what insulation and pressure rating the tank needs, which design code and approvals apply at the site, and which level, relief, filling and withdrawal connections must be fitted.
Stationary bulk tanks for liquid carbon dioxide, polyurethane- or polystyrene-insulated and vacuum-insulated, with their instruments and connections. Gas cylinders, CO₂ recovery and liquefaction plants, relief valves supplied separately and general pressure vessels (see pressure vessel) are outside this page.
01
Pentair describes its liquid CO₂ storage tanks as on-site buffers for when CO₂ consumption is lower than the liquid supply rate, offered with three insulation types: pre-insulated with 120 mm polyurethane (150 mm for 110 m³) under 1 mm aluminium cladding; site-installed 150 mm polystyrene with vapour barrier, 20 mm mineral wool and 1 mm aluminium cladding; or vacuum-insulated cryogenic design, vertical only, with fine-grain perlite and a vacuum of at least 5 × 10⁻² mbar(a). [1]
Pentair lists design pressure of 20 bar(g), or 25 bar(g) for the vacuum-insulated type, design temperature −40/+40 °C, seismic zone UBC 2 and design code PED 97/23/EC, with other approvals on request. [1]
EN 13458-2 applies to the design, fabrication, inspection and testing of static vacuum-insulated cryogenic vessels for a maximum allowable pressure above 0.5 bar, is not applicable to toxic fluids, and is cited under the Pressure Equipment Directive 2014/68/EU. [2]
Editorial calculation: 20 bar(g) ≈ 2.0 MPa (≈ 290 psig) and 25 bar(g) ≈ 2.5 MPa (≈ 363 psig); −40 °C is −40 °F and +40 °C is 104 °F. [1]
Give the supplier the required capacity, insulation type, design pressure and temperature, design code and local approvals, seismic and wind zone, orientation (vertical or horizontal), level, weighing and relief requirements, filling and withdrawal connections, and site footprint.
02
Pentair's scope of supply lists a differential-pressure liquid level indicator with a safety switch against overfilling, optional load cells for horizontal tanks, a double-mounted safety relief valve with change-over valve, necessary valves and fittings, a manhole for inspection, and connections for the CO₂ plant (liquid and gas), a truck filling station and a cylinder filling station; its separate cylinder filling unit pump is rated 600 kg/h. [1]
Editorial calculation: a 600 kg/h cylinder filling pump transfers 10 kg of liquid CO₂ per minute at its rated capacity. [1]
03
EIGA Doc 66/22, Refrigerated carbon dioxide storage at users' premises, covers outdoor refrigerated liquid CO₂ vessels up to 40 bar design pressure and up to 125,000 litres water capacity (pressures in bar gauge). It gives a design range of 15 to 25 bar for storage vessels, corresponding to −30 °C to −15 °C, and states that under normal conditions the pressure should stay above 10 bar; if it falls below that value the user should stop withdrawal and contact the gas supplier. [3]
EIGA warns that dry ice plugs can form in hoses and piping if liquid CO₂ pressure drops below the triple point and can be ejected with enough force to injure people; it requires pipes and hoses to be pressurised with gas above 5 bar before liquid is introduced, and liquid to be purged before the pressure is reduced below 5 bar. It also states that relief valves must be installed so dirt and moisture cannot collect on the seat and ice cannot envelop them, and that carbon steel vessels taken out of service may be held at 1–2 bar of inert gas against corrosion. [3] This complements the insulation and fittings described above. [1] [2]
Editorial calculation: 125,000 L is 125 m³; the 10 bar minimum leaves about 5.8 bar above the triple point pressure.
The NIST Chemistry WebBook lists the triple point of carbon dioxide at 216.58 K and 5.185 bar, and its critical point at 304.18 K and 73.80 bar (with other measurements from 304.1 to 304.35 K and 73.40 to 73.825 bar). [4] Editorial calculation: 216.58 K is −56.57 °C, and 5.185 bar absolute less 1.013 bar of atmosphere is about 4.17 bar gauge, which agrees with the 4.18 bar at −56.6 °C given in EIGA's table, so EIGA's figure is a gauge pressure. [4] [3]
Editorial calculation: the critical temperature of 304.18 K is about 31.0 °C, above which CO₂ cannot be held as a liquid at any pressure; this is why bulk tanks are insulated and refrigerated to the −30 °C to −15 °C range EIGA gives, and why Pentair's +40 °C upper design temperature concerns the vessel shell, not liquid storage. The 73.8 bar critical pressure is also about 2.8 times the 25 bar(g) top of the design range (about 26 bar absolute), which shows how far an unrefrigerated tank would have to rise in pressure. [4] [3] [1]
| EIGA Doc 66/22 point | Value |
|---|---|
| Scope | Outdoor vessels up to 40 bar design pressure, up to 125,000 L |
| Storage vessel design pressure | 15–25 bar (−30 °C to −15 °C) |
| Minimum operating pressure | Keep above 10 bar; stop withdrawal below it |
| Triple point | 4.18 bar at −56.6 °C (solid CO₂ forms) |
| Maximum fill level | Set so relief valves discharge gas; 90–95% of vessel volume |
| Vacuum in interspace | < 0.05 mbar (abs) multilayer; 0.2 mbar (abs) perlite |
| Relief valves | At least two per bulk storage vessel, connected to the gas phase |
| Triple point (NIST reference) | 216.58 K (−56.57 °C) and 5.185 bar absolute [4] |
| Critical point (NIST reference) | 304.18 K (about 31.0 °C) and 73.80 bar [4] |
Ask the supplier for the design pressure, maximum fill level setting, relief valve arrangement and a low-pressure alarm set point above the 10 bar EIGA gives.
04
No manufacturer record has been reviewed for this product yet. Send your specification and CNFX will match it against manufacturer records.
Ask any supplier for the design code and certificates, design pressure and temperature, insulation type and thickness or vacuum level, materials of inner and outer vessels, relief valve set pressure and capacity, level and weighing instruments, connections, dimensions, empty weight and transport arrangement.
05
This is a functional reference built from the sources cited; it is not one maker's specification.
| Part | Role | Fix in the order |
|---|---|---|
| Pressure vessel | Holds liquid CO₂. [1] [2] | Design pressure; code. |
| Insulation | Limits heat gain. [1] | PU; polystyrene; vacuum-perlite. |
| Level indicator | Shows contents; prevents overfill. [1] | DP type; switch. |
| Relief valves | Protect against overpressure. [1] | Twin with change-over. |
| Connections | Fill and withdraw. [1] | Liquid, gas, truck, cylinder. |
06
A liquid CO₂ tank quotation needs values for your site. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Design Temperature (°C) | e.g. −40/+40 °C. [1] | Range. |
| Storage Capacity (m³) | e.g. sizes up to 110 m³ referenced. [1] | Gross and net capacity. |
| Filling Ratio | Not stated in the reviewed sources. | Maximum fill. |
| Material | Not stated in the reviewed sources. | Inner and outer vessel. |
| Insulation Thickness (mm) | e.g. 120 mm PU (150 mm on 110 m³); 150 mm polystyrene + 20 mm mineral wool. [1] | Type; thickness. |
| Safety Valve Set Pressure (MPa) | Design pressure 20 or 25 bar(g); twin relief valves. [1] | Set pressure; capacity. |
| Leakage Rate (mL/min) | Not stated in the reviewed sources. | Test result. |
| Weight (kg) | Not stated in the reviewed sources. | Empty and full weight. |
| Footprint (m²) | Vacuum type vertical only. [1] | Layout. |
| Maximum fill level | 90–95% of vessel volume, so relief valves discharge gas (EIGA Doc 66). [3] | Fill level setting; overfill protection. |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Capacity: [m³ or tonnes] Insulation: [PU; polystyrene; vacuum-perlite] Design: [pressure; temperature; code] Orientation: [vertical; horizontal] Instruments: [level; load cells; relief valves] Connections: [plant; truck; cylinder filling] Site: [seismic zone; footprint]
No manufacturer record has been reviewed for this product yet. Send your specification and CNFX will match it against manufacturer records.
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
Pentair lists 20 bar(g), or 25 bar(g) for its vacuum-insulated type, at −40/+40 °C. [1]
Pentair offers 120 mm polyurethane, site-installed 150 mm polystyrene with mineral wool, or vertical vacuum-perlite insulation. [1]
EN 13458-2 covers static vacuum-insulated cryogenic vessels above 0.5 bar maximum allowable pressure. [2]
EIGA Doc 66/22 states the pressure should remain above 10 bar under normal conditions; below the triple point (4.18 bar, −56.6 °C) solid CO₂ forms and dry ice plugs can block lines. [3]
NIST lists CO₂'s critical temperature at 304.18 K (about 31 °C); above it CO₂ cannot stay liquid, so bulk tanks are insulated and held well below that. [4]
Sources checked 2026-10-12. Pentair supplies liquid CO₂ storage tanks; EN 13458-2 is the European standard for static vacuum-insulated cryogenic vessels; EIGA Doc 66/22 is the industry code for refrigerated CO₂ storage at users' premises; the NIST Chemistry WebBook gives the reference triple- and critical-point data for CO₂.
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