Cryogenic liquids are stored and transported in a wide range of containers from small Dewar flasks to railroad tank cars. Only equipment and containers designed for the intended product, service pressure, and temperature should be used. If any questions arise about correct handling or transport procedures, or about the compatibility of materials with a given cryogen, the gas supplier should be consulted.

Cryogenic liquids ordinarily should not be handled in open containers unless they are specifically designed for that purpose and for that product. Cryogenic containers should be clean and made from materials, such as austenitic stainless steels, copper, and certain aluminum alloys, suitable for cryogenic temperatures.

Cryogens should be transferred into warm lines or containers slowly to prevent thermal shock to the piping and container and to eliminate possible excessive pressure buildup in the system. When liquids are transferred from one container to another, the receiving container should be cooled gradually to prevent shock and reduce flashing. High concentrations of escaping gases should be vented so that they do not collect in an enclosed area.

• Do not drop warm solids or liquids into cryogenic liquids. Violent boiling will result and liquid can splash onto personnel and equipment.
• Avoid breathing vapor from any cryogenic liquid source except for liquid-oxygen equipment designed to supply warm breathing oxygen. When cryogenic liquids are being discharged from drain valves or blowdown lines, open the valves slowly to prevent splashing.

Smoking should never be permitted.

Two types of portable liquid-storage vessels are generally used to hold and dispense cryogenic liquids-nonpressurized Dewar containers and pressurized liquid cylinders.

Dewar containers for liquids are open-mouthed, non-pressurized, vacuum-jacketed vessels usually used to hold liquid argon, nitrogen, oxygen, or helium. Some of these containers are designed for lightweight liquids such as helium and for maximum holding times; their internal support system cannot hold some of the heavier cryogens, such as argon. When they are used be sure that no ice accumulates in the neck or on the cover and causes a blockage and subsequent pressure buildup.

Laboratory Dewar flasks with wide-mouthed openings have no cover to protect the liquid. Most are made of metal, but some smaller units are of glass.

Liquid cylinders are pressurized containers, usually vertical vessels, designed and fabricated according to Transport Canada specifications. There are three major types: for dispensing liquid or gas, for gas withdrawal only, and for liquid withdrawal only. Each type of liquid cylinder has appropriate valves for filling and dispensing and is adequately protected with a pressure-control valve and a frangible disc.

Some liquid cylinders can be handled manually, but it is preferable to move them using portable handcarts. A strap should be used to secure the cylinder to the handcart to keep it from slipping off.

Liquid cylinders should never be lifted by the ring by crane. Lifting hook connections are supplied on some models. Consult the manufacturer of the vessel or gas supplier for specific recommendations.

An unusually cold outside jacket on a cryogenic vessel indicates some loss of insulating vacuum. Frost spots may appear. A vessel in this condition should be drained, removed from service, and set aside for repair. Such repairs should be handled by the manufacturer or qualified company.

Cryogenic containers must be handled very carefully. They should not be dropped or tipped on their sides.