Regeneration starting conditions vary for cryogenic pump applications. For continuous degassing, the cryogenic pump needs to be regenerated as long as one of the following two conditions is generally met: (1) cryogenic pump with no additional heat load , The temperature of the secondary cold head exceeds 20 K or the primary cold head temperature exceeds 130 K; (2) The pressure inside the pump is above 1 × 10 -4 Pa after the high vacuum valve is closed for 5 min. For some intermittent pumping process, because of the high vacuum valve is opened, the temperature of the cold head will certainly fluctuate and the recovery time of the cold head temperature is closely related to the amount of pre-adsorbed gas, the maximum amount of gas sucked by the cryogenic pump, Therefore, in these cases, it is also necessary to determine the regeneration conditions according to the fluctuation time allowed under actual conditions. For non-automatically controlled cryogenic pump extraction systems, in general, cryogenic pump manufacturers will provide a regenerated reference time, but due to differences in the actual situation, the operator is required to judge based on actual experience whether the end of regeneration, and some High degree of automation of the cryogenic pump system can automatically determine. Generally in the regeneration to a certain stage, the cryogenic pump crude pumping to a suitable pressure value, close the roughing valve, measuring the rate of pressure rise and the controller stored in the empirical value comparison, if you do not meet the conditions , You need to continue the cryogenic pump heating. This process can also be used to determine the pressure value after a certain period of time. Taking into account the vacuum on the deflation measurement accuracy requirements and shorter time requirements, at about 1 Pa test is more appropriate. Regeneration mode using heating belt heating, due to the pump after the empty heating effect is not good, so to determine the start time, the time interval between two judgments need to be determined according to the actual situation, the use of pump heating plate heating regeneration without consideration These two questions.
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