Engi-Seal Face RVB09

Overview

Load vs Deflection

Most spring-energized sealing profiles are designed to be compatible with the three primary spring types. Understanding the differences between these spring types is essential for making informed engineering decisions, particularly in relation to each spring’s load versus deflection characteristics.

Load vs. deflection characterizes how a seal’s spring energizer responds under compression, providing a measure of the force (load) required to achieve a certain deformation (deflection) of the spring element within the seal. This response is pivotal for ensuring adequate sealing pressure against the mating surface throughout the operational life of the seal, compensating for wear, hardware tolerances, and thermal expansions or contractions.

Significance in Seal Design

1. Sealing Pressure: The spring’s load-deflection characteristics determine the initial and operating sealing force applied by the seal lip to the mating surface. This force must be sufficient to prevent leakage without causing excessive wear or friction.
2. Compensation for Wear and Tolerance: Over time, seal materials may wear down, and machine components may experience dimensional changes due to temperature fluctuations or mechanical stress. A spring with an appropriate load-deflection curve ensures that the seal maintains effective pressure against the mating surface, compensating for these variations.
3. Material Compatibility: The choice of spring material and its load-deflection properties must be compatible with the seal jacket material to prevent over-compression or insufficient loading, ensuring the longevity and reliability of the seal.

Analyzing Load vs. Deflection

• Linear vs. Non-linear Response: Springs can exhibit a linear relationship between load and deflection (where force increases proportionally with displacement) or a non-linear response (where the relationship deviates from proportionality due to design or material characteristics).
• Spring Types: Different spring types (e.g., helical, cantilever, canted-coil) offer distinct load-deflection curves. The selection of a spring type is based on the specific application requirements, including expected pressures, motions (static, dynamic, rotary, reciprocating), and environmental conditions.
• Design Optimization: By analyzing the load-deflection characteristics, engineers can optimize the seal design for specific applications, ensuring that the seal provides the necessary performance over its expected service life. This involves selecting the right spring type, material, and dimensions to achieve the desired load at a given deflection.

Load Variations Based on Spring Load

Each spring type can be customized to provide different load profiles depending on the specific load requirements:

• Light Load: Provides minimal sealing force, ideal for applications where low friction is essential and the sealing pressure is not critical.
• Medium Load: Offers a balanced sealing force suitable for most applications, providing a good compromise between load and friction.
• Heavy Load: Delivers maximum sealing force, suitable for high-pressure environments where a robust seal is necessary.

Spring Energizer Types

Canted Coil Springs

• Description: KC Seals DynaFlex canted coil springs provide a flat load curve when compressed, ideal for consistent, predictable loads over a wide deflection range. Made from 300 series stainless steel and other alloys, they offer excellent corrosion resistance.
• Applications: Suitable for dynamic reciprocating and rotary applications, as well as static applications with wide gland tolerances or misalignment. Ideal for friction-sensitive applications.
• Features: Provide compression load near the center of the seal with minimal gaps, maximizing spring contact. Suitable for small seal diameters and dynamic rod seal applications under 1/2″ diameter.
• Recommendations: Best for friction-sensitive applications, rotary shafts up to 1000 sfpm, and dynamic applications with diameters under 1/2″ or cross-sections under 3/32″.

Helical Springs

• Description: Helical springs are coiled wires providing uniform sealing force, high load capacity, and resilience.
• Applications: Best for static applications, slow or infrequent dynamic conditions, vacuum, and cryogenic applications.
• Features: Produces evenly distributed load with small gaps between coils, ideal for tight seals in challenging conditions.
• Recommendations: Suitable for static rods and pistons, slow dynamic applications under 200 sfpm, and critical sealing scenarios.

V-Springs (Cantilever Springs)

• Description: Made from flat strip material in a V shape, offering moderate to high sealing force. Load adjustment can be made by altering the leg angle or material thickness.
• Applications: Suitable for dynamic applications (rotary or reciprocating motion) and static conditions with high deflection requirements.
• Features: The long beam leg design places the spring load at the leading edge of the seal, ideal for use as a scraper with an optional scraper lip.
• Recommendations: Used for reciprocating rods and pistons, rotary shafts under 100 sfpm, abrasive media (with scraper lip), and dynamic applications above 450°F.

Key Points

• Canted Coil Springs: Best for friction-sensitive and dynamic applications.
• Helical Springs: Ideal for static and slow dynamic applications.
• V-Springs: Versatile for both dynamic and static conditions, with high deflection capability.

Understanding these spring types and their specific applications can help you make informed decisions for optimal sealing performance.

Spring Materials

Materials: Available in 302 SS, 316 SS, Alloy C-276, Beryllium Copper, and other alloys. Offered with gold, silver, and nickel plating for electronic and semiconductor applications. Radial cross-sections from 1/32″ to 3/8″, with diameters as small as 0.050″.

Material Benefits:

• Stainless Steel: Low cost, high tensile strength, general service.
• Beryllium Copper: High strength, good electrical conductivity, limited temperature range.
• Nickel Alloy: Superior corrosion resistance, suitable for corrosive environments.
• Cobalt Nickel Alloy: Excellent for hydrogen sulfide environments, used in medical implants and petrochemical applications.
• Titanium Alloy: High strength and corrosion resistance, used in military, aerospace, and medical devices.