Many types of filling or transfer lines are used to handle the flow of cryogenic fluids from one point to another - small, insulated copper or stainless steel lines; large-diameter rigid lines; or flexible hose systems, vacuum jacketed lines, or other insulated systems.

Liquids can be transferred by three methods; the simplest is gravity. In this case, the height of the stored liquid serves as the transfer medium. Pressurized transfer uses the vapor pressure of the product, or pressure from an external source, to move the liquid to the lower-pressure receiving container.

Various types of cryogenic pumps are also available. Flow rates may vary from less than one to several hundred gpm. The product should be in liquid form in the transfer lines. Any vaporization of liquid within the system may cause excessive pressure drop and two-phase (liquid and gas) flow and cavitation that is detrimental to the operation of cryogenic pumps.

Short transfer lines used for intermittent service are normally not insulated, but lines used for continuous transfer of cryogens usually are. All liquid transfer hoses should have dust caps.

Vacuum-jacketed lines are required to transfer liquid hydrogen and liquid helium because of their extremely cold temperatures and low heats of vaporization. Vacuum lines occasionally are used for in-plant transfer of atmospheric cryogenic fluids to reduce costly line and flash-off losses.