Liquefied natural gas (LNG) and other very low temperature fluids are of increasing commercial importance. There is, therefore, a need for increased facility in handling, storing, and transporting such liquids. For example, LNG is being increasingly utilized as an alternative fuel source for internal combustion engines. Governmental regulations require that LNG be transported at pressures of about 30 psi, but to decrease the amount of LNG that is evaporated or otherwise lost from a storage tank, it is common to store the LNG at pressures of 150 psi. When "bottled" for use as the fuel tank of an internal combustion engine, it is common to pressurize the LNG to pressures as high as 220 psi. Of course each increase in pressure requires that the LNG be pumped into the tank at the next higher pressure such that successful use of LNG as an alternative fuel depends, in effect, upon reliable, safe and energy efficient pumping of high volumes of such fluids.
Pumps are presently available but all suffer from a variety of disadvantages and limitations which limit their life, require frequent maintenance, and otherwise decrease their utility. For instance, many pumps are available for pumping LNG, but so far as is known, the life of all such pumps is limited by the need for frequent maintenance and/or replacement of the seals. Heretofore known seal-less pumps have not provided a satisfactory solution to this problems For instance, magnetic drive pumps are known in the pump art, but their use at very low temperatures is made problematical by the failure of the bonding material utilized on the magnets at that temperature and, in the case of LNG, by the almost complete lack of lubrication that is provided by the LNG passing through the pump.
It is, therefore, an object of the present invention to provide a pump for use at very low temperatures which is not limited by the disadvantages of known pumps. More specifically, it is an object of the present invention to provide a magnetic drive pump for use in pumping at very low temperatures.
Another object of the present invention is to provide a magnetic drive pump useful at temperatures lower than about -100.degree. C.