Schematic diagram of the spiral groove structure Of course, the sealing surface groove can be opened not only on the moving ring but also on the stationary ring. In general, at high speeds, slots are formed on the moving ring sealing surface; at low or medium speeds, slots can be formed in the stationary ring. The basic principle of dry gas sealing The dry gas sealing is achieved by the rotation of the shaft to create a gas film between the sealing surfaces of the static and dynamic rings. After the rotation (ie, the rotation of the moving ring), the sealing gas (dry gas) is sucked to the root of the rotating ring of the moving ring, and the pressure of the airflow is increased due to the blockage of the airflow by the root, which is called the opening and closing force. The opening and closing force acts on the mirror surface of the static ring to create a film gap between the moving and static ring contact faces. When the closing force (spring force + air static pressure) used for the other side of the stationary ring is equal to the opening and closing force, the force acting on the stationary ring reaches the dynamic balance, and the air gap is determined. The gas dynamics study of the T-slot structure shows that when the gap between the two ends of the dry gas seal is 2~3μm, the gas flow layer passing through the gap is the most stable. Therefore, the design value of the dry gas seal film thickness is generally selected at 3μm. about. Under dynamic equilibrium conditions, the sealing force can be expressed as follows: If interference occurs and the film gap is reduced, the opening and closing force increases due to the compression of the gas film, so that Fc=Fo reaches a new equilibrium, as shown: If the air gap is increased due to certain conditions, the opening and closing force is reduced due to the expansion of the air film, so that Fc=Fo, and the new balance dry gas seal is re-established. Compared with other seals, the dry gas seal has Long life, low leakage, low energy consumption, low wear, low pollution, simple and reliable operation, low maintenance, etc., are gradually replacing traditional sealing forms such as floating ring seals and labyrinth seals. But at present its cost is still too high. Long-life Gases that form a gas film from a low-energy, low-pollution dry gas seal interface generally use a dried and filtered process gas. The source is generally the compressor outlet line, and the power is the gas's own pressure. Therefore, compared with the floating ring seal and the oil bath type mechanical seal, it is not necessary to use a complicated lubricating oil system, cooling water, etc., and the sealing gas does not require additional external power, so the energy consumption is low. According to the literature, the energy consumption of dry gas seals is about 5% of mechanical seals. In addition, the gas leaking into the cylinder is the same as the process medium, does not cause pollution of the process gas, and does not require additional purification of the compressed gas; a small amount of gas leaking outward from the side of the cylinder is usually nitrogen for sealing. These can greatly reduce the leakage of certain flammable and explosive toxic media, protect the personal safety of the personnel, and ensure the safe operation of the factory. The low leakage is different from the general lubrication mechanical seal. It is easy to make direct contact between the two sealing surfaces, so that the friction heat of the dry gas seal cannot be removed in time, and the end face contact is not lubricated, which will quickly cause sealing deformation and excessive heat generation of the end face, resulting in seal failure. Dry Gas Sealed Application Dry Gas Sealed Auxiliary Configuration The typical process for a dry gas seal system is shown. Its accessory configuration is generally a dry gas sealed control cabinet. The control cabinet consists of a flow regulating valve, a pressure control valve and a high-precision filter. Its function is to automatically control and regulate the flow and pressure of the dry gas required for dry gas sealing. The high-precision filter ensures the cleanliness of the gas and the accuracy of the filter. The rating is generally ≤ 2μ. The dry gas sealed cabinet is small in size and light in weight, easy to install, inspect and repair. The dry gas seal is connected to the sealed cabinet by a number of stainless steel pipelines. The specification of the pipeline is determined by the pressure and flow rate of the seal gas required for dry gas. The general diameter is less than 1 inch (2514 mm). Dry gas sealing operation precautions a1 to ensure the quality of the sealing gas, without any mechanical impurities and water, oil, steam, etc.; b1 to ensure the minimum allowable flow of the sealing gas, to ensure the formation of the gas film, and to the positive direction of the machine cavity Leakage; c1 Before the compressor lubricating oil system is operated, it is necessary to open the isolated nitrogen on both sides of the dry gas seal to prevent the oil and gas from entering the dry gas sealed cavity and ensure the drying of the sealed cavity; d1 for the dry seal of the single spiral The unidirectionality of the compressor rotation must be ensured to prevent reversal. Dry Gas Sealed Fault Diagnosis During the use of dry gas seals, there are many causes of failures. In summary, they are broadly classified into mechanical faults and process faults. The diagnosis of mechanical faults is collectively referred to as mechanical (sealing) failure due to improper installation of seals or damage to dry gas seals caused by mechanical reasons of the compressor. This type of failure often occurs during the first test of the compressor or the first drive after the repair. Faults caused by improper seal installation Dry gas seal installation should be carried out in a clean and dust-free environment, and equipped with a set of special tools, any particulate impurities entering the seal will damage the seal. Before installation, first check the appearance of the sealing body to ensure clean, dry and non-polluting; then, remove the protective platen, and use both hands to press down on the outer casing of the sealing body to ensure good elasticity. That is, it is detected whether the spring after sealing the static ring has good performance. Again, check whether the O-ring outside the seal is suitable and has good elasticity and toughness, otherwise it will be replaced; finally, the sealing body is positioned, and the positioning in the sealing body is divided into axial positioning of the moving ring and axial positioning of the stationary ring. Positioning dimensions must be strictly enforced on drawings or random documents. Spherical Plain Bearing,Spherical Roller Bearing,SKF Spherical Roller Bearing Thrust Ball bearing Co., Ltd. , http://www.cnrollerbearing.com