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A2025-10-13
As critical equipment in industrial production and scientific research, the performance of vacuum pumps is directly related to the operational efficiency of the entire system. The sealing system is a core component of a vacuum pump, preventing both the ingress of external gas into the vacuum system and the leakage of the pump's internal medium into the environment. This article systematically introduces the types, material selection, and maintenance key points of vacuum pump seals, providing a professional reference for relevant technical personnel.
Vacuum pump seals can be divided into two main categories: static seals and dynamic seals, each suited for different operating conditions and requirements.
Static seals are used between relatively stationary parts, primarily in the following two forms:
O-ring seals are the most common type of static seal. Their cross-section is O-shaped, simple to manufacture, low-cost, yet capable of providing excellent sealing performance. In static seal applications, O-rings can withstand pressures up to 100 MPa and have an operating temperature range of approximately -60 to 200 °C. Their sealing principle relies on the rebound force generated by pre-compression during installation, creating contact pressure on the sealing surface to block leakage paths.
Gasket seals are the basic form of static sealing in centrifugal pumps. They rely on the plastic deformation of the material to fill micro-irregularities on the flange sealing surface. The selection of gasket material requires comprehensive consideration of factors such as medium properties, operating temperature, pressure, and corrosiveness.
Dynamic seals are used between parts with relative motion. They involve higher technical requirements and come in a greater variety.
Mechanical seals are the most precise form of dynamic sealing in modern vacuum pumps. Composed of rotating and stationary rings, secondary seals, transmission components, etc., they form a seal through the relative sliding of the end faces. Mechanical seals have very low leakage rates and a long service life, but they are more expensive to manufacture and require strict installation precision.
Packed seals are one of the oldest forms of sealing. They place compressible and resilient packing material into a stuffing box, converting the axial compression force from the gland into radial sealing force. Their structure is simple, easy to replace, inexpensive, and broadly adaptable, but they have a certain leakage rate and are not suitable for applications requiring extremely high tightness.
Oil seals are a type of self-tightening lip seal. They are compact, low-cost, and can prevent both medium leakage and the ingress of external contaminants, but they have poor pressure resistance and are typically used in low-pressure environments.
Advanced sealing technologies include labyrinth seals, dynamic seals (e.g., expeller seals), spiral seals, and dry gas seals. As a representative of non-contact seals, dry gas seals work by pumping gas into extremely thin gas films (only 1–3 micrometers thick) formed via hydrodynamic grooves on the outer side of the end faces, achieving zero leakage or zero emission of the medium. They are particularly suitable for high-parameter operating conditions.
The performance of seals largely depends on material selection, which requires comprehensive consideration of multiple factors:
For the friction pair (rotating and stationary rings) in mechanical seals, silicon carbide and high-grade anti-blistering graphite are common choices. For applications involving particles, high-viscosity media, and high-pressure conditions, a hard-face pairing like silicon carbide against silicon carbide is often used. These materials possess high hardness, excellent wear resistance, and chemical stability.
Used for O-rings, secondary seals, etc. Fluoroelastomer is a common choice due to its good overall properties. When operating temperatures or chemical compatibility requirements exceed the limits of fluoroelastomer, perfluoroelastomer can be used, with a maximum operating temperature of up to 290°C.
For highly corrosive media, specialized plastics such as Polytetrafluoroethylene and Polyether ether ketone must be selected. For high-temperature applications, metal materials (such as stainless steel) or expanded graphite can be chosen. For the food and pharmaceutical industries, sealing materials that meet hygiene standards are required.
Seal selection requires balancing multiple factors: vacuum level requirements (rough vacuum, high vacuum, or ultra-high vacuum), transmitted medium characteristics (corrosiveness, presence of particles), operating temperature range, pressure conditions, and cost constraints. For example, when handling corrosive media, the material's corrosion resistance is the primary consideration; whereas in high-temperature conditions, the material's temperature resistance becomes the key factor.
Correct installation and standardized maintenance are crucial for ensuring the long-term stable operation of the sealing system:
When installing mechanical seals, installation deviation must be avoided, ensuring the concentricity of the gland with the shaft or sleeve. The spring compression must be adjusted strictly according to specifications, with minimal error. The flatness and cleanliness of the sealing faces directly affect the sealing performance; any minor scratches or impurities can lead to seal failure.
A hydrostatic test should be performed before startup to check for leaks. The pump should be turned by hand to check for smooth and even rotation. Ensure the seal chamber is filled with liquid before startup to avoid dry running and damage to the seal faces.
Minor leakage is acceptable immediately after pump startup, but it should decrease significantly after several hours of continuous operation. If leakage persists, the pump should be stopped for inspection. Monitor the temperature change at the seal area closely during operation; abnormal heating often indicates a seal problem. Avoid pump run-out conditions to prevent damage to the seal faces from dry friction.
Establish a scientific regular maintenance system, including: periodic inspection of seal leakage, monitoring temperature at the seal area, and recording seal service life. For mechanical seals in critical equipment, predictive maintenance can be considered, using vibration analysis, temperature trend monitoring, and other means to identify potential problems in advance.
The vacuum pump sealing system is a complex field involving multi-disciplinary technologies. The selection, installation, and maintenance of seals directly affect the performance and service life of the vacuum pump. With the continuous development of new materials and processes, vacuum pump sealing technology is advancing towards zero leakage, long life, and high reliability. A deep understanding of the principles and characteristics of various sealing technologies, combined with scientific selection and standardized maintenance based on actual operating conditions, is the key to ensuring the efficient and stable operation of vacuum systems.
For specific application scenarios, it is recommended to communicate deeply with professional seal suppliers, leverage their expertise and experience, and select the most appropriate sealing solution to optimize lifecycle costs while ensuring equipment performance.
[DLSEALS kindly Reminder] Sealing issues? Turn to DLSEALS! As a sealing component manufacturer, we specialize in customizing sealing components, providing a full range of services from design, research and development, production, testing, and more. If you have more information you'd like to know, feel free to contact us directly. DLSEALS's product experts are dedicated to serving you!
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