What is a cryogenic pump?
A type of centrifugal pump that is primarily used to pump very low temperature liquids. They are made with special materials and internal clearances selected to be able to accommodate these low temperature liquids. Other materials might readily fail in these low temperature environments.
How do they work?
Cryogenic pumps have one or more impellers which raise the velocity of the liquid as it passes along the impeller vanes. From there the fluid is directed through the pump volute or diffuser where the velocity is reduced and converted into pressure through a diffusion process. This process is virtually the same as it is in other centrifugal pumps. Furthermore, they are available in many of the same general configurations as other centrifugal pumps, including end suction, submersible, vertical column sump, and vertical turbine types.
Unlike other types of centrifugal pumps, cryogenic pumps are able to work at very low temperatures that occur in cryogenic services, typically several hundred degrees below zero, or lower.
Special attention must be taken by the pump manufacturer in the selection of materials for the components, as ordinary pump materials would quickly fail at these low temperatures. Also, the running clearances must be adjusted carefully by the manufacturers to account for the dramatically different thermal expansion and contraction of materials at these low temperatures. Special elastomers must be used to accommodate the low temperatures. Finally, special attention must be made to protect these pumps against cavitation, since many cryogenic fluids will boil if the temperature drops just a small amount.
Where are they used?
Cryogenic pumps are used in applications where low temperature liquids must be transported. They are very commonly found in the production and transport of liquid natural gas (LNG), liquid Nitrogen, liquid Helium, and liquid Oxygen. They are also used in metals processing plants and applications where very pure substances need to be produced or extracted. This makes them useful in fields such as the semiconductor industry, electron microscopy, and mass spectrometry. And, they are sometimes used to pump specialty heat transfer fluids that operate at extremely low temperatures.
Ruhrpumpen manufacturers and sells cryogenic pumps for liquid nitrogen, liquid oxygen, hydrocarbons, and other liquid gas applications. The companyís VLT Cryogenic and VLTV line process pumps comply with the API-610 standards.
Ruhrpumpenís VLT pump has a vertical arrangement and low temperature design. The pump provides exception efficiencies and low cost operation in high head applications. The VLT allows for max flow to 7,000 gpm, 4,000 ft. of head, and pressure to 1,500 psi.
The VLTV cryogenic pump has a flow capacity to 2,420 gpm, heads up to 4,900 feet, and pressures to 2,020 psi. The pump can handle discharge flange sizes from 2 inches to 8 inches.
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