In the design of the universal seal (spring energy storage seal), the driving force behind its outstanding performance does not come from the sealing body itself, but from an indispensable key component within it - the precisely designed core spring. It endows the universal seal with unique advantages and reliability beyond traditional seals. This article will deeply analyze the structure, materials, and core role of the spring in the universal seal.
I. Structure of the Spring: A Precisely Designed Power Source
The spring inside the universal seal is not an ordinary compression or tension spring; instead, it has a specially designed structure to provide continuous and uniform radial force:
1. Basic shape: U-shaped or V-shaped:
• U-shaped spring (horseshoe shape): This is the most classic and widely used structure. Its open U-shaped design provides excellent elasticity and recovery ability.
• V-shaped spring: Similar to the U-shaped one, but the corner is sharper (V-shaped), which can provide higher initial elasticity and is often used in situations requiring greater preload.
2. Core functional characteristics:
• Pre-compression design: The spring is already in a pre-compressed state before being inserted into the sealing body groove. This is the basis for its ability to provide continuous force.
• Ring-shaped closed structure: The U/V-shaped structures are connected at the head and tail (often through precise spot welding or special bonding), forming a complete ring, ensuring that the radial force applied to the sealing body is highly uniform and continuous, without weak points.
• Matching with the sealing body groove: The spring is precisely embedded in the specially designed grooves on the inner side of the sealing base (usually PTFE or other high-molecular materials), and the two cooperate to form an efficient whole.
II. Material selection under strict requirements:
Due to being in the core of the seal, the working environment may involve harsh conditions such as pressure, temperature, and corrosive media, so the spring material must possess special properties:
1. Key Requirements:
• High elasticity & excellent fatigue resistance: Capable of withstanding millions or even billions of compression-expansion cycles without permanent deformation or fracture, ensuring the long-term stability of sealing force.
• Corrosion resistance: Resistant to the corrosion of sealing media, environment, and possible cleaning agents. This is particularly important in the chemical, pharmaceutical, and food industries.
• High temperature stability: The material must maintain its elasticity and strength within the operating temperature range without significant degradation. This is especially crucial when dealing with high-temperature steam, hot oil, and other conditions.
• Low creep/anti-stress relaxation: The material must have a strong ability to resist permanent plastic deformation under long-term stress application, preventing the gradual attenuation of sealing force over time.
2. Common Materials:
• Austenitic stainless steel: This is the most commonly used option, providing excellent comprehensive performance.
• AISI 304 (1.4301): General-purpose, suitable for general corrosive environments and moderate temperatures.
• AISI 316/316L (1.4401/1.4404/1.4435): The most mainstream choice. Contains molybdenum, significantly enhancing resistance to pitting and intergranular corrosion, with a wider application range, especially suitable for chemical, marine, food and pharmaceutical industries.
• High-temperature/high-performance alloys: For extreme conditions.
• Inconel X-750 / 718: Nickel-based high-temperature alloy, with outstanding high-temperature strength, creep resistance, stress relaxation resistance, and corrosion resistance. Suitable for aerospace, high-temperature oil well equipment, etc.
• Elgiloy/Phynox: Cobalt-chromium-nickel alloy, with extremely high strength, unparalleled fatigue resistance, excellent corrosion resistance, and anti-relaxation properties. The top choice for long-life, high-reliability requirements (such as nuclear power plant seals).
• Hastelloy: Mainly used in strong corrosive environments (such as strong acids, halogen media).
3. The Core Role of Springs: Irreplaceable Driving Force
The internal springs of the universal seal are not supporting roles but undertake the key task of determining the overall sealing performance:
1.
Provide a constant initial sealing force (key differentiating point):
• This is the core advantage that the universal seal differs from traditional O-rings or lip seals.
• When the equipment is not yet activated, the system has no pressure or is in a low-pressure state, the spring's own preload force will continuously and stably expand outward (radial force), driving the lip of the sealing body to tightly adhere to the mating surface (shaft/rod and cavity wall).
• Function: Perfectly solves the "dry seal" problem during the startup stage and the insufficient sealing force under low pressure, ensuring zero leakage during startup and the reliability of low-pressure sealing. 2.
Compensation for pressure fluctuations and deficiencies in the system:
• When the system pressure rises, the medium pressure will assist in pushing the sealing lip to fit more tightly together.
• However, when the system pressure drops, fluctuates, or even disappears (such as during shutdown or pressure pulsation), the constant force of the spring will immediately "take over" to make up for the lack of pressure.
• Function: To maintain the sealing contact force always within the effective range, ensuring no leakage occurs during system pressure changes or during shutdown. This is the core guarantee for the reliability of dynamic sealing. 3.
Compensation for wear and plastic deformation of the sealing body:
• The sealing body (especially made of PTFE and other materials) will experience slight wear at the contact surfaces over a long period of use, and the material itself may also undergo minor permanent deformation (cold flow, creep).
• The spring is like an "energy storage device" that never gets tired. Its inherent rebound force will continuously follow through, constantly pushing the sealing body to fill these tiny gaps and deformations.
• Function: Significantly extends the service life of the sealing element and maintains long-term sealing effectiveness. 4.
Maintain a uniform and continuous distribution of sealing force:
• Its ring-shaped closed-loop structure design ensures that the radial force applied to the sealing body is highly uniform, and there are no dead angles around the sealing ring when rotating 360 degrees.
• Function: To avoid the intensification of local wear or leakage channels caused by uneven sealing force, especially suitable for working conditions with ellipticity or slight surface fluctuations.
Conclusion: The true source of power
The performance label of the universal seal - long life, low leakage, adaptability to wide pressure differences, high temperature resistance, etc. The real supporting force behind it is precisely its internal precision springs. It goes beyond the limitations of relying solely on system pressure or the elasticity of the sealing body, providing an active, continuous, and adaptive core driving force. The structural design, material selection, and quality control of the springs directly determine the limit and application range of the universal seal's performance. Understanding and valuing this "core heart" is the key to correctly selecting and applying the universal seal.
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