What is the structure of a hot-mounted sealing ring?
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To increase the operating temperature of seals with O-ring seals, hot-mounted seals have been developed. It transmits torque and achieves sealing through the interference fit between the cemented carbide ring and the ring seat, and it is the most commonly used type of sealing ring at present (Figure 23). When assembling this type of sealing ring, the ring seat is heated, causing the hole in the seat to expand due to thermal expansion. The cemented carbide ring is then inserted, and after cooling, the two components are joined together through interference fit. Subsequently, they are ground and polished at room temperature to achieve the desired precision of the sealing surface. The disadvantage of this type of ring is that, over time and due to changes in ambient and operating temperatures, the flatness of the sealed surface will change and fail to meet the requirements. The reason for this is that the hot-fit structure itself has an interference fit, and the contact stress is uneven, resulting in mechanical deformation ； Secondly, due to high (or low) operating temperatures, differences in the physical properties of the material (mainly the linear expansion coefficient) prevent the mating surfaces of the cemented carbide ring and the ring seat from expanding and contracting simultaneously. As a result, the amount of interference changes, and so does the contact stress; these changes affect the performance of the sealing ring. Deformation of the sealed end face compromises the flatness; in more severe cases, the interference is lost, resulting in failure of the connection and the detachment of the cemented carbide ring. There are currently three types of hot-mounted sealing rings; Figure 23a shows the design produced by manufacturers in the early days, which is relatively simple in structure. However, due to the contact between the cemented carbide ring and the auxiliary seal ring, once the cemented carbide ring becomes loose, the auxiliary seal ring is severely worn during operation, resulting in significant leakage. Figure 23b is an improvement over Figure 23a: the auxiliary sealing ring does not come into contact with the cemented carbide ring, so the aforementioned defects are absent. There is only slight leakage between the cemented carbide ring and the ring seat. To reduce the uneven deformation of the sealing surface of the cemented carbide ring, annular grooves are provided on the inside and outside of the heat-fitting portion of the ring seat (Figure 23c), thereby making the contact stress on the outer cylindrical surface of the cemented carbide ring more uniform and reducing the deformation of the tungsten carbide ring, which results in better performance.
The structure of a hot-mounted sealing ring mainly includes the following elements: 1. Cemented carbide ring: It is typically made from cemented carbide materials such as tungsten carbide, which possess high hardness and excellent wear resistance, allowing them to withstand high temperatures and chemical erosion. 2. Ring seat: It is the component in which the cemented carbide ring is installed, and is usually made of metal material. During assembly, the ring seat needs to be heated so that the cemented carbide ring can be inserted into it. After cooling, the interference fit between the two, caused by thermal expansion and contraction, ensures torque transmission and sealing performance. 3. Auxiliary sealing ring: Used to provide initial sealing; it is usually made of elastic materials such as rubber or PTFE (polytetrafluoroethylene). There are three existing types of hot-mounted seal ring structures, namely: a. the simple structure from earlier times (Figure 23a), in which the cemented carbide ring is in direct contact with the auxiliary seal ring; if the cemented carbide ring becomes loose, it can cause the auxiliary seal ring to wear out, leading to leaks. b. The improved structure (Figure 23b) features a secondary sealing ring that does not come into direct contact with the cemented carbide ring, thereby avoiding the drawbacks of the earlier design. However, there may be slight leakage between the cemented carbide ring and the ring seat. c. To reduce the uneven deformation of the sealed end face, a further improved structure (Figure 23c) features annular grooves provided on the inside and outside of the hot-fitting area of the ring seat, which makes the contact stress on the outer cylindrical surface of the cemented carbide ring more uniform, thereby reducing the deformation of the cemented carbide ring and improving its performance. These structures are designed with account taken of the expansion and contraction of materials caused by temperature changes, as well as the requirements for transmitting torque and achieving sealing. Different structures optimize the performance of the sealing ring to suit various operating conditions and environments. .