A high-efficiency cold core replacement method for gm refrigerators

Abstract

The invention discloses a high-efficient replacement method for a cooling core of a Gifford-Mcmahon(GM) refrigerator. The high-efficient replacement method which changes heat exchange of the prior art comprises the following steps: after the GM refrigerator is disassembled and pressure relief is finished, continuously blowing in helium of which the pressure is 0.5 to 1 kilogram and the purity is 99.995% to 99.999% to one end of a cylinder close to a gas distribution plate, and taking away an organic glass plate; later taking the cooling core in the cylinder, increasing the pressure of the blown helium to 5 to 8 kilograms, continuously blowing in gases, after observing that the inner wall of the cylinder is clean, reducing the pressure of the introduced helium to 0.5 to 1 kilogram; then mounting a new cooling core prepared in advance to the inner part of the cylinder, and quickly mounting the gas distribution plate and a motor which are cleaned at the end of the cylinder, and stopping the helium supply; assembling the GM refrigerator. The invention aims at providing the high-efficient replacement method for the cooling core of the GM refrigerator which requires short time in operation flow to reduce the equipment downtime so as to avoid the liquid helium consumption, reduce the cost required for replacement and improve the success rate of a replacement process.

Description

technical field [0001] The invention belongs to the technical field of an operation method for replacing parts of a GM refrigerator, and in particular relates to a high-efficiency method for replacing a cold core of a GM refrigerator that can shorten the replacement time and reduce the consumption of liquid helium. Background technique [0002] In the magnet refrigeration process of the NMR instrument, the use of the GM refrigerator is very common, but due to the limitation of the service life of the cold core, when the cooling effect of the GM refrigerator is weakened due to the cold core, the cold core should be replaced in time to ensure For the cooling effect of GM refrigerator, in the prior art, only heat exchange is the way to replace the cold core. One method of so-called heat exchange is: after removing the exhaust pipe and intake pipe of the GM refrigerator and releasing the pressure, The GM refrigerator heats the cylinder body through the heating module installed o...

AI Technical Summary

Problems solved by technology

[0002] In the magnet refrigeration process of the NMR instrument, the use of the GM refrigerator is very common, but due to the limitation of the service life of the cold core, when the cooling effect of the GM refrigerator is weakened due to the cold core, the cold core should be replaced in time to ensure For the cooling effect of GM refrigerator, in the prior art, only heat exchange is the way to replace the cold core. One method of so-called heat exchange is: after removing the exhaust pipe and intake pipe of the GM refrigerator and releasing the pressure, The GM refrigerator heats the cylinder body through the heating module installed outside the cylinder body. After heating from the working temperature of the cylinder body at 10K to normal temperature, disassemble the motor and the gas distribution panel, clean up the impurities inside the gas distribution panel and the cylinder body, and put the The pre-prepared new cold core is installed inside the cylinder and connected to the gas distribution panel and the motor. Although this method in the prior art completes the replacement of the cold core, the operation process is cumbersome and requires heating of the GM refrigerator. It takes a long time to heat up from the working temperature of 10k to normal temperature, resulting in the entire replacement process taking 5-6 hours, which increases the downtime of the equipment, and due to the operation of technicians and the influence of the external environment during the replacement process, the success rate of replacement is reduced. Less than 90%, if the replacement fails, it will need to be replaced again, which seriously affects the service life of the equipment. During the replacement process, the GM refrigerator is heated by the heating module installed outside the cylinder, and the temperature becomes room temperature. The process and the GM refrigerator cannot work for a long time, resulting in serious consumption of liquid helium in the nuclear magnetic resonance instrument, the total consumption reaches 3%-4% of the total volume of liquid helium, which seriously increases the replacement cost of the cold core; another existing Technical replacement method The heating method is direct heating with a hair dryer. This method consumes 5-6% of the total volume of liquid helium, and seriously increases the replacement time, reaching more than 10 hours, which further increases the loss of enterprise benefits.