BULK CO2 SYSTEM

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Carbon dioxide is stored in a single container at 17°C. Two completely independent fridge systems are fitted for cooling, one in use, the other stand by. A power supply from the emergency switchboard must be available for the plant. In the event of total loss of power the tank is sufficiently well insulated to maintain a temperature for a minimum of 24 hours before "boil off” occurs.

Two sets of relief valves are fitted to the pressure vessel. Set A lifts at 24.5 bar, to atmosphere. Set B lifts at 27 bar to the CO₂ room, in case of fire in this space. Each set has an isolating cock to enable one valve only of the set to be opened up for survey/repair. A third relief valve C set at 33 bar, protects the system pipe lines.

There are two means of indicating tank level:

i)                    Remote electrical display of contents (usually of the capacitance type).

ii)                  A stand by indicator, consisting of a vertical, external un‑insulated pipe. This can be filled with CO₂ to the vessel level, by opening one valve. Level is determined by frosting on the outside of the pipe.

Alarms are fitted for 5% loss of contents and for over filling of the vessel above 98%.

The quantity of CO₂ released is controlled either by opening the valves for a pre‑determined time or by automatic control based on tank contents. The remote operated valves in the system can all be opened manually, using a spanner provided at each valve.

The storage vessel is fabricated from low temperature nickel steel, suitable for low temperature operation. The system is emptied and internally inspected every ten years. Pipe system is of solid drawn galvanised steel pipe.