How does the SF6 recovery unit work?- SF6在线监测系统_SF6检漏仪_SF6传感器_SF6密度继电器

韦弗斯新闻动态

最新动态

SF6安全保障专家

专注于SF6气体检测的专业化

135 85763546

How does the SF6 recovery unit work?

发布时间：2018-06-28 来源：ydlcb 浏览次数：35次

There are two main working principles of SF6 gas recovery device:

The first adopts the principle of refrigerated liquefaction method: that is, in the process of SF6 gas recovery, under a certain SF6 gas pressure, the refrigeration unit is used to reduce the temperature of SF6 gas to the saturated steam temperature under the pressure,SF6 gas begins to liquefy into a liquid, and is stored in a liquid form;

The second method adopts the principle of high-pressure liquefaction method, that is, in the process of SF6 gas recovery, at the ambient temperature at that time, the compressor is used to increase the pressure of SF6 gas to the saturated steam pressure at that temperature, and SF6 gas begins to be converted into liquid and stored in liquid form.

Comparative analysis:

The foreign representative manufacturers using the principle of frozen liquefaction method are LIMCO, MICAFIL, Switzerland, KAJI, Japan. The advantages are: the advantages are fast recovery speed and fast liquefaction speed; The disadvantage is that the refrigeration parts and refrigerant must be increased in this way, and the failure rate of the refrigeration parts is increased

High pressure liquefaction method adopts the principle of high pressure liquefaction method of foreign representative manufacturer WINFOSS company, the product structure is simple, simple operation. Because there are no refrigeration parts, the recovery vehicle is smaller in size, The disadvantage is that the working pressure of the system is high and the recovery efficiency is low. When the SF6 gas temperature (the temperature of SF6 gas after compression by the compressor can reach more than 80 ° C) exceeds the critical temperature of 45.55 ° C, it cannot be liquefied. At this time, the SF6 gas at high temperature and high pressure can only be liquefied after a period of time until its temperature drops below the critical temperature Convert to liquid.

Comparison of oil and oil free systems

Use of oil or oil-free systems in recovery systems;

Oil-free system can theoretically achieve SF6 gas to 100% no contact with Oil, known as oil-free (oil-free), such as the domestic use of film compressor. This kind of recovery device has large volume, low recovery efficiency and heavy maintenance workload. In this way, a second oil-free system has emerged, and the host of the recovery device -SF6 gas compressor is a grease lubricated piston compressor, such as the piston ring in direct contact with SF6 and other self-lubricating materials, only the crankshaft in the crankcase, the crank pin, the piston pin and other rotating parts of the crankcase are lubricated by grease (no lubricating Oil in the crankcase), called oil-free (oil-LE) ss), which should be accurately called underberth. Long-term use, in theory, there are trace oil vapor mixed with SF6, in practice, the trace oil vapor has little effect on Sf6.

The used SF6 gas contains a certain amount of water, which will form a strong corrosive acid with the decomposition, causing corrosion to the inlet and outlet valve of the overhead press of the SF6 recovery vehicle that is being recovered. Under high pressure, the oil in the oil air compressor will enter the cylinder with SF6, and when SF6 is refilled, the oil mist will also enter the air chamber with SF6; In order to prevent such accidents, manufacturers generally adopt two ways: 1, use oil-free air compressors and vacuum compressors, and 2, add oil filters between the recovery car and the air chamber. However, no matter how much you add the oil filter, you can't completely remove the oil as clean as before.

Such compressors have high manufacturing process requirements and are mostly imported compressors. The advantage is small size, light weight, the disadvantage is high price, because there is no oil, the service life is greatly reduced compared with the oil compressor.

The use of a recovery device with an oil system has the advantage of long service life and durability.

The disadvantage is that it is necessary to add a set of oil filtration system, which is more complex, and the oil filtration system needs to be designed reasonably to ensure that the oil is clean and thoroughly removed. When the customer is using the SF6 recovery truck to recover SF6, and the air compressor or vacuum compressor is working suddenly artificial or faulty power failure, WINFOSS SF6 recovery truck will automatically start the check valve to prevent the SF6 gas backflow, if you are using an air compressor or vacuum compressor with oil, then the oil in the air compressor or vacuum compressor will also backflow into the air chamber

Function of main parts

1) Check valve

When a power failure occurs, the WINFOSS SF6 recovery vehicle automatically starts the check valve to prevent the return of sf6 gas, and if you are using an air compressor or vacuum compressor with oil, the oil from the air compressor or vacuum compressor will also return into the air chamber.

2) Pre-filter

The role of the pre-filter is to improve the purity of the recovered SF6 gas and filter out more decomposition. When SF6 is used for a long time, the decomposed substances will be relatively many, it is difficult to completely filter the gas by the filter of the recycling vehicle itself, in order to ensure that the purity of the recycled gas can achieve the role of recycling, it is very necessary to install a pre-filter in front of the SF6 gas recovery vehicle. It is important to note that this point is common to all SF6 recycling vehicles. Moreover, the placement of the pre-filter can also extend the service life and number of filter elements on the SF6 recycling vehicle.

The pre-filter includes a dry filter and a dust filter. Dry filter is mainly used for the filtration of water in SF6 and gaseous substances in SF6 decomposition, such as SF4, HF, SO2F2, SOF2, SO2 and CF4; Make the moisture content less than 10ppm. The filter material is alumina and molecular sieve. Dust filter is mainly used for the filtration of solid dust and decomposition in SF6 gas. For dust ≥1um in diameter, the blocking rate is 100%.

Preparation before recycling

1, understand the use time of the switch, the general switch operation 2000 times need maintenance.

2, to a certain service life, the SF6 gas should be detected. Such as (gas, water, gas medium) to determine whether recovery is required.

For the above reasons, the following preparations should be made before recycling:

1) The measurement of decomposition products is to find out how much secondary decomposition is contained in the switch, to determine whether the insulation and arc extinguishing performance of SF6 gas can ensure the normal operation of the switch, and to know whether there is a local discharge in the switch.

2) Measure the purity of SF6, mainly to judge the purity of SF6. We all know that SF6 gas with a purity of less than 98% cannot be used because there is too much decomposition and water in it to ensure the normal operation of the switch.

3) To measure the dew point temperature is to know the water content of SF6 gas in the switch, because a large amount of water may produce condensate on the surface of the insulation parts in the equipment, attached to the insulation surface, resulting in flashover along the surface, greatly reducing the insulation level of the equipment, while the presence of water will accelerate the decomposition reaction of SF6 under the action of the arc, and generate a variety of strongly corrosive and toxic impurities. Such as hydrogen fluoride, cause chemical corrosion of equipment, and endanger the personal safety of staff.

As an excellent insulating and arc extinguishing medium, SF6 gas is widely used in the circuit breakers of GIS equipment and separated equipment. In order to ensure the safe operation of equipment and the personal safety of staff, the quality of SF6 gas must be inspected.

First of all, it is necessary to detect the SF6 water content, because the excessive water content in SF6 gas will cause serious adverse consequences, which are manifested in two aspects:

1, a large amount of water may produce condensate on the surface of the insulation parts in the equipment, attached to the insulation surface, resulting in flashover along the surface, greatly reducing the insulation level of the equipment.

2, the presence of water will accelerate the decomposition reaction of SF6 under the action of the arc, and generate a variety of strongly corrosive and toxic impurities, such as (HF) hydrogen fluoride, causing chemical corrosion of equipment, and endangering the personal safety of staff.

Secondly, the analysis of secondary decomposes in SF6 gas, because the secondary decomposes will be deposited at the bottom of the switch when they react with metal particles, causing partial discharge, and this process is a vicious cycle, and more secondary decomposes will be generated after decomposition. Of course, when these secondary decomposes react with water, Metal fluoride, hydrogen fluoride, and other highly corrosive and toxic products will be produced, which will corrode the bottom of the switch and cause harm to the staff after leakage.