A pump that pumps a liquid colder than -50 F; perhaps even colder than -100F

The submerged motor pump design does include the motor in the same vessel as the pump which do not require any seal or coupling. Submerged motor pumps (SMP) are differentiated by its diffuser design. The diffuser is converting kinetic energy into static pressure and guiding the liquid after the impeller outlet towards the next impeller stage or the outlet of the pump.

LNG – liquid natural gas, LEG – liquid ethylene gas, LPG – liquid petroleum gas (Propane, butane, ethylene) and LN2 or LIN – liquid nitrogen.

The cryogenic pumps are used in LNG liquefaction and regassification plants, petrochemical plants, refineries, LNG Carriers and LNG Floating storage unit FSRU and FLNG

A cryogenic pump is typically used for pumping the LNG or LPG from the storage facility, to either a truck for transferring the liquid from the plant to a customer, or to a power plant (which pumps the liquid first to its storage tanks, and then to its heat exchanger) in order to convert the liquid into a gas so that it can generate power or supply the gas in the local community for its usage in home appliances.

JC Carter was the first company developed the submerged Cryogenic pumps

The manufactures of the cryogenic pumps for LNG and LPG are: Nikkiso, Ebara Elliot Energy, and Cryostar.  Ebara is the current largest submersible cryogenic pump manufacturer.

Typically, it consists of a storage tank with an in-tank pumps placed in a column either to transfer the liquid to a heat exchanger in order to convert the liquid into a gas, or to transfer the liquid to the tanks of a truck or train.

The in-tank pumping system consists of foot valve, cryogenic pump with integral motor, cryogenic cable with support assembly, headplate, cryogenic terminal header, power junction box and instrumentation junction box.

The cryogenic pump spares are classified as hydraulic spares (Impellor, Inducer and diffuser), Electrical spares (Motor, shaft-rotor assembly, cryogenic cables, cryogenic terminal header / feedthrough and junction box), Wear items (bearings, wear rings, diffuser bushings, Gaskets, and hardware), Instrumentation spares (Accelerometer, Accelerometer cable), Thrust balancing components (Balance drum, lower bearing housing assembly, throttle plate and baffle plate)

Minor maintenance is done after 5,000 to 8,000 hours or about 3 to 5 years of operation. The major overhaul is typically performed after 20,000 hours of operation.

Cryogenic bearings: Typically, there are 2-3 ball bearings in a pump and are replaced in every after 5,000 to 8,000 hours maintenance

Diffuser wear rings and bushing: Each stage contains a diffuser that has a wear ring and a shaft bushing that needs to be replaced. The amount of wear in the wear ring is different for each stage, so typically at least 3/4 of all the stages must have both the wear ring (which limits the leakage between the impeller and the wear ring) and the shaft bushing (which is in every diffuser housing to support the pump shaft).

Impellor and balance drum: On a rare occasion, an impeller must also be replaced as well as the balance drum housing (which houses the lower ball bearing.)

One pump could take 3 to 5 days.