The following problems should be paid attention to in the structural design of cryogenic liquid pumps:
(1) To ensure uniform cold shrinkage of parts at low temperature, the structure shall be symmetrical;
(2) The inlet and outlet pipelines of the pump must be compensated for cold shrinkage, such as metal bellows compensation.
(3) Connecting parts between normal temperature zone and low temperature zone should be made of materials with low thermal conductivity to reduce thermal conductivity loss;
(4) Reduce heat capacity of parts working in low temperature zone as much as possible to reduce vaporization loss of liquid and shorten starting time;
(5) Parts operating in low temperature zone with relative movement, also select materials with similar linear expansion coefficient as far as possible to fabricate;The linear expansion coefficient of the enveloped part must be less than or equal to that of the enveloped part to prevent jamming during cold shrinkage.
(6) Important parts working at low temperatures, especially moving parts requiring very strict coupling, such as moving and stationary rings of shaft seals, piston and cylinder liners of piston pumps, must be cold treated before final finishing.The cold treatment temperature should generally be lower or equal to the working temperature for 1 to 4 hours.
(7) In order to prevent the vaporization of cryogenic liquid, special attention should be paid to the insulation of pump body and inlet pipeline. Generally, pearlite sand or foaming material is used. Vacuum insulation is usually used for low temperature liquid hydrogen pump and liquid helium pump.
(8) Seal is one of the key problems in the design of cryogenic pump. Seal of pump is closed or shaft seal.There are three types of shaft seal: mechanical seal (both dry and wet), labyrinth seal and stuffing box seal.Mechanical seals are commonly used for lower temperature pumps.
