Cryogenic Pump Knowledge Hub

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

The design of a submerged motor pump integrates the motor and pump within the same vessel, eliminating the need for seals or couplings. Submerged motor pumps (SMPs) are distinguished by their unique diffuser design, which converts kinetic energy into static pressure and directs the liquid from the impeller outlet to either the next impeller stage or the pump’s output.

LNG – liquid natural gas, LEG – Liquid Ethylene Gas, LPG – Liquid Petroleum Gas (Propane, Butane, Ethylene) and LN2 or LIN – Liquid Nitrogen.

Cryogenic pumps are used in LNG liquefaction and regasification plants, petrochemical plants, refineries, LNG carriers, and floating storage units such as FSRUs and FLNGs.

A cryogenic pump is typically used to transfer LNG or LPG from a storage facility to either a truck for transportation to a customer or a power plant. In power plants, the liquid is first pumped into storage tanks and then to a heat exchanger, where it is converted into gas for power generation or supplied to local communities for use in home appliances. The three primary types of = cryogenic pumps are the in-tank pump, the pot-mounted pump (also known as the suction vessel-mounted pump), and the send-out pump.

JC Carter was the first company that invented the submerged cryogenic pumps.
The cryogenic pumps for LNG and LPG are manufactured by Nikkiso, Ebara Elliot Energy, and Cryostar. Ebara is now the largest maker of submersible cryogenic pumps.

Typically, it consists of a storage tank with in-tank pumps placed in a column, either to transfer the liquid to a heat exchanger for conversion into gas or to transfer the liquid to the tanks of a truck or train. The in-tank pumping system consists of a foot valve, a cryogenic pump with an integral motor, a cryogenic cable with a support assembly, a headplate, a cryogenic terminal header, a power junction box, and an 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, a pump has 2-3 ball bearings, which are replaced every 5,000 to 8,000 hours during maintenance.

Diffuser Wear Rings and Bushings: Each stage contains a diffuser with a wear ring and a shaft bushing that need to be replaced. The amount of wear in the wear ring varies for each stage, so typically, at least 3/4 of all stages require replacement of both the wear ring (which limits leakage between the impeller and the wear ring) and the shaft bushing (which is present in every diffuser housing to support the pump shaft).

Impeller and Balance Drum: On rare occasions, the impeller must also be replaced, along with the balance drum housing, which houses the lower ball bearing.

Performing a thorough inspection, repair, and assembly of a cryogenic pump can take anywhere from 2 to 4 days. However, a full overhaul may require 3 to 4 months, primarily due to the lead time needed to obtain hydraulic and electrical spare parts, which can take 3 months or longer.

Installing a cryogenic pump involves inspecting it before setting up the vibration and electrical systems, a process that typically takes around 2 days. Commissioning the pump(s) includes verifying the vibration monitoring system, ensuring proper drying and cooldown, starting up the pump, and confirming site performance. This step usually requires an additional 2 days.

Marine cargo and spray pumps typically undergo maintenance every five years. As part of this process, the cryogenic bearings and gaskets are replaced. On average, it takes about 2 days to complete the maintenance of a single pump.