Dynamic sealing issues

Seals are mainly divided into static seals and dynamic seals. Static seals are simple in design, involving things like rubber rings and packing; dynamic seals, on the other hand, are much more complex. The most commonly used types today are mechanical seals and dry gas seals. In centrifugal compressors, dry gas seals are used almost exclusively, while pumps employ either mechanical seals or dry gas seals. The main manufacturers in China that design and produce dry gas seals are Sichuan Nihonki (Sichuan Sealing Technology Institute). They were the first entities in the country to engage in research and development of dry gas seals, but they entered the market relatively late. Currently, they account for around 50% of the domestic market for dry gas seals.

I’ve heard that magnetic seals are very effective and can replace the leak-prone mechanical seals, but I haven’t used them myself.

Are there any recent advances in dynamic sealing technology? Could any experts provide some information on this? The sealing between the surfaces in relative motion is called dynamic sealing. Dynamic seals are classified into reciprocating motion seals and rotating motion seals based on their mode of movement ； Seals are classified into contact seals and non-contact seals based on whether the seal element is in contact with the components that move relative to it ； Based on the contact orientation of the seal, it can be classified into face sealing and circumferential sealing, etc. The specific classifications are as follows: I. Contact seals: 1. Packing seals include felt seals, gland packing seals, and molded packing seals. 2. Mechanical seals, oil seals (dust-proof seals), expansion ring seals, slip ring seals. II. Non-contact sealing: 1. Centrifugal sealing (impeller centrifugal sealing, slinger seal) ； 2. Labyrinth seal ； 3. Spiral seal ； Pneumatic seal ； Hydraulic sealing ； Compared to traditional sealing methods, electromagnetic sealing is a non-contact aerodynamic sealing technology that utilizes aerodynamic principles to achieve sealing by means of the air film formed at the end faces of two non-contacting sealing pairs during mechanical operation. The sealing medium for contactless aerodynamic sealing is gas, rather than sealing rings or similar components used in traditional sealing systems. Recently, new advancements have been made in sealing technology, with Wood’s contactless aerodynamic sealing technology being a representative example. Its working principle involves two ring-shaped components that form a pair of counterpart elements; on the end face of the rotatable ring (the rotor ring), several grooves designed in accordance with aerodynamic principles are created using a laser engraving machine. The depth of the groove is 0.005–0.01 mm. The other ring is fixed to the engine housing and does not move (stator ring). When the two rings move relative to each other (rotate) along the axis, the external airflow flows into the groove along the periphery of the rotor ring, eventually coming to a stop at the top of the groove, thereby forming a gas valve. According to aerodynamic principles, air cannot flow back, and pressure is generated instantly between the two rings, creating an air film. This gas film maintains the gap between the two rings at 0.003–0.01 mm, thereby achieving a contactless seal. Wood’s contactless aerodynamic sealing technology in improving the efficiency of engines or other equipment ； Reduce pollution ； It is **superior to traditional sealing technologies** in reducing the overall cost of sealing. Contactless aerodynamic sealing technology can be widely applied to engines and gas stations in various industries.

Among current dynamic sealing technologies, dry sealing is the one that is developing fastest; magnetic sealing is still in the stage of research and development

Dry gas seals for compressors have developed rapidly and are quite reliable; they have essentially replaced mechanical seals and floating ring seals. Mechanical seals are still the most common type of seal for pumps, but dry gas seals are also being widely used in some critical applications. Magnetic sealing has not been seen yet.