As the standard equipment of SF6 gas recovery equipment, gas storage tanks have existed for many years. As people's inertial thought, it is customary to think that gas storage tanks are necessary for SF6 gas recovery equipment. Few people will raise the following questions to question the existence of gas storage tanks:
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(1) The storage capacity of SF6 gas storage tank equipped in general SF6 gas recovery equipment is limited, of which about 300L is the majority, and the top of the gas storage tank with this capacity can store and recover a SF6 liquefied gas with 220 KVGIS interval at most. After the gas storage tank is filled, it is necessary to empty the gas storage tank to carry out the next recovery operation. In practice, very few gas in the gas storage tank is just recharged from scratch into SF6 gas storage tank. 6. Opportunities in gas insulated electrical equipment (together with guaranteeing the quality of SF6 gas recovered), it is reasonable to recover SF6 gas from the gas storage tank to store in SF6 special cylinder from scratch, but this will add twice the recovery time, and may also reduce the purity of SF6 gas recovered during the second recovery operation. For the sake of simplicity, SF6 gas in gas storage tanks is often discharged directly into the atmosphere to pollute the environment.
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(2) When the residual SF6 gas in defective electrical equipment is recovered, the quality of SF6 gas recovered into the gas storage tank will be poor and can not be directly reused. It is necessary to recover all SF6 gas in the gas storage tank to the SF6 special cylinder for storage and then send it to the professional treatment center for treatment. Together, it is necessary to open the gas storage tank for thorough cleaning. Otherwise, the quality of SF6 gas recovered again cannot be guaranteed. Quantity, this is not an easy process.
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(3) At present, most provinces in China have set up SF6 gas recovery and treatment centers, so in order to ensure the safety of SF6 gas insulated electrical equipment, users no longer use SF6 gas recovered into the gas storage tank when inflating, but use SF6 gas in the newly manufactured SF6 special cylinder or SF6 gas qualified after treatment by the treatment center. Therefore, when the gas is recovered, it is required to be directly poured into SF6 special steel cylinder for storage, and then sent to the treatment center for treatment. The gas tank has become a surplus and a burden.
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(4) Because of the existence of gas storage tank, the shape size of SF6 gas recovery equipment will increase a lot, and the component of the whole machine will be added 40-50% (especially after the liquefied SF6 gas is filled in the gas storage tank, which makes it difficult for SF6 gas recovery equipment to move in the work site.
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(5) The gas storage tank is a pressure vessel. The pressure of SF6 gas in the gas storage tank will increase with the increase of ambient temperature. The pressure can reach about 4 MPa in summer when the ambient temperature is high. Major accidents will occur if the equipment undergoes severe vibration or bumping during transportation and hoisting, or if the rated working pressure of the gas storage tank decreases due to the long-term corrosion of the gas storage tank (the safety valve is invalid under the above conditions). In addition, according to the relevant national rules, pressure vessels need to be inspected and judged by the relevant departments within the time limit of the rules, and the current situation is that few people have applied for inspection and judgement. The first batch of gas storage tanks on SF6 gas recovery equipment has been used for nearly 20 years, far beyond the time of the national rules for inspection and judgement, and no one has realized that they have been buried. There are great potential safety hazards.
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In summary, SF6 gas recovery equipment equipped with gas storage tanks in practice has more disadvantages than advantages, and should be equipped or not as little as possible. Direct liquefaction of recovered SF6 gas into SF6 special cylinders can solve all the above problems. It is also easy to collect empty SF6 special cylinders after inflating, but only people's inertia ideas need to be changed.
