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背托环

背托环
分类: 橡胶定制件
应用领域: 汽车应用零件 工业零件 轴承密封 机械密封
BEST RING INDUSTRIAL CORP.
BEST RING INDUSTRIAL CORP.
国家: 台湾
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Back-up Rings

Back-up Rings are auxiliary sealing components installed alongside elastomeric seals, such as O-rings or X-rings. While they do not provide a primary seal themselves, they are critical for protecting the main seal and ensuring performance in high-pressure environments.

Operating Principle

When pressure is applied, the primary seal (e.g., O-ring) tends to flow toward the lower-pressure side. If the clearance gap (extrusion gap) between metal parts is too large, the rubber material will deform and be squeezed into the gap, leading to damage. Back-up rings fill or significantly reduce this gap to keep the seal in its original groove.

Back-up Ring Operating Principle

Core Functions

  • Extrusion Prevention:
    Acts as a rigid barrier to bridge or minimize the seal clearance.
  • High-Pressure Support:
    Made of hard materials capable of withstanding extreme pressure while keeping the elastomeric seal intact.
  • Extended Service Life:
    Prevents extrusion-related wear, significantly increasing system reliability and seal longevity.
  • Enhanced Stability:
    Provides extra structural support to the sealing element, improving overall system integrity.
  • Application Versatility:
    Used in both static and dynamic applications with various seal types (O-rings, X-rings, etc.).

Classification & Types of Back-up Rings

Back-up rings are classified by their structure and the specific pressure requirements of the sealing system:

Type Solid Ring (Uncut) Scarf Cut Ring Split / Spiral Ring
Visual Illustration Solid Ring Scarf Cut Ring Spiral Ring
Product Solid Product Scarf Product Spiral Product
Key Features A continuous, uncut solid ring. Features a diagonal cut at both ends to form a scarf joint. Cut radially or manufactured in a spiral shape for expansion.
Applications Ideal for disassemblable shafts/pistons; provides the highest structural support. For non-disassemblable installations; superior sealing over straight-cut rings. Perfect for on-site installations; easily passes over shaft shoulders.

Installation Layouts

  • Single Pressure Configuration:
    One back-up ring is installed on the low-pressure side (one side only) of the O-ring.
  • Double Pressure Configuration:
    Two back-up rings are installed on both sides of the O-ring to protect it from pressure applied from either direction.
Installation Layouts

Diagram: Single vs. Double Pressure Layout

Recommended Operating Conditions

Choosing the right material and recognizing the appropriate conditions for back-up rings is essential for optimal equipment performance:

Operating Conditions Diagram
High Pressure:
Exceeding 5MPa (50 bar).
Large Gaps:
Wide extrusion gaps due to tolerances.
Dynamic Wear:
High-speed/long-stroke motions.

Industry Applications

Hydraulic

Pneumatic

Aerospace

Oil & Gas

Automotive

Material Selection Guide

Material Temp Range (°F) Comments and Typical Uses
Nitrile (NBR) -20 to 212 Highly abrasion-resistant; ideal for petroleum-based applications.
HNBR -20 to 300 Superior chemical/heat resistance and extrusion protection vs. standard Nitrile.
Viton® (FKM) -15 to 400 Outstanding resistance to high temperatures and aggressive chemicals.
POM / PEEK -100 to 550 High-modulus materials for extreme strength and wear resistance in specialized industrial use.
PTFE (Teflon) -400 to 450 Broadest chemical compatibility and lowest friction; handles extreme temp swings.
Back-up Ring Icon

Back-up Ring (Anti-Extrusion Ring) FAQ

Q1: What is the primary purpose of a Back-up Ring?
The primary function is to prevent extrusion of the main elastomeric seal (O-ring/X-ring) into the hardware's clearance gap. It acts as a rigid barrier to maintain structural integrity.
Q2: When is it necessary to use a Back-up Ring?

Highly recommended in these scenarios:

  • ⚙️ High Pressure: When system pressure exceeds 5MPa (50 bar).
  • ⚙️ Large Gaps: When machining tolerances result in wide extrusion gaps.
  • ⚙️ Extreme Temperatures: In heat where rubber seals soften.
  • ⚙️ Dynamic Applications: High-speed or long-stroke motions.
Q3: How do I determine the installation position and quantity?
Single-acting:
Install 1 ring on the low-pressure side.
Double-acting:
Install 2 rings, one on each side.
Q4: What are the common types of Back-up Rings?
  • ⚙️ Solid (Uncut): Provides the best 360° support; requires hardware disassembly for installation.
  • ⚙️ Scarf Cut: Features a diagonal cut; ideal for easy retrofitting without full disassembly.
  • ⚙️ Spiral Ring: Multi-turn design; compensates for large tolerances, ideal for on-site maintenance.
Q5: What materials are typically used?
PTFE (Teflon):
Most popular choice; offers extremely low friction and high chemical resistance.
Nylon / PA:
Higher mechanical strength and better extrusion resistance than PTFE.
POM / PEEK:
Engineered for extreme durability, high pressure, and high-temperature service.

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