PTFE Back-up Rings
Product Details & High-Performance Features
Our PTFE Back-up Rings act as the structural backbone of high-pressure sealing systems, specifically engineered to eliminate the most common cause of seal failure: Extrusion Damage.
- • Anti-Extrusion Sovereignty: By effectively closing the "Extrusion Gap" on the low-pressure side, our rings prevent the "nibbling" or "shaving" of O-rings that typically occurs during severe pressure spikes.
- • Coefficient of Friction Management: Leveraging PTFE's molecular self-lubrication (μ ≈ 0.05), these rings reduce breakaway friction and prevent "stick-slip" vibrations, which is critical for precision control in flight actuators.
- • Dynamic Response & Shape Memory: Our rings are processed using a specific sintering cycle that imparts a "shape memory" effect, ensuring the ring returns to its original geometry after pressure is released.
- • Total Media Compatibility: Inherently resistant to synthetic hydraulic fluids, Skydrol, aggressive hydrocarbons, and sour gas (H2S), maintaining zero swelling across the entire pH 0-14 range.
- • Shaft Protection Technology: The non-abrasive nature of our PTFE compounds ensures that even at pressures of 500+ Bar, the surface finish of the reciprocating rod (Ra 0.1-0.4) remains uncompromised.
Material Science: Engineering the Modulus of Resistance
Standard O-rings fail at high pressures because elastomers lose their modulus. We solve this by using PTFE compounds that maintain structural rigidity under extreme compressive loads:
- • Virgin PTFE (Unfilled): Offers maximum chemical purity and the lowest possible friction. Ideal for medical and laboratory equipment where contamination is a risk and pressures are below 150 Bar.
- • Glass Fiber Filled (15-25%): Enhances compressive strength and thermal stability. The glass fibers act as structural "micro-pillars," preventing the PTFE matrix from flowing under load.
- • Bronze-Filled PTFE (40-60%): The "Gold Standard" for heavy-duty hydraulics. Bronze significantly improves hardness (Shore D 70+) and heat dissipation, allowing the ring to withstand pressures up to 600 Bar in static applications.
- • Carbon/Graphite Filled: Specifically designed for high-speed reciprocating seals. The carbon filler provides superior dry-running protection and electrical conductivity to prevent static build-up in fuel systems.
Technical Specifications & Critical Engineering Data
This matrix provides the quantitative data required for system validation and groove dimensioning.
Table 1: Technical Operating Matrix & Permissible Extrusion Gaps
|
Material Grade |
Hardness (Shore D) |
Max Pressure |
Permissible Gap |
Friction Coeff. |
| Virgin PTFE | 55 - 60 | 150 Bar | 0.05 mm | 0.05 - 0.10 |
| Glass-Filled | 62 - 68 | 350 Bar | 0.15 mm | 0.12 - 0.18 |
| Bronze-Filled | 68 - 75 | 600 Bar | 0.25 mm | 0.10 - 0.15 |
| Carbon-Filled | 64 - 70 | 400 Bar | 0.20 mm | 0.08 - 0.12 |
| PEEK (Ultra-High) | 85 - 90 | 1000+ Bar | 0.40 mm | 0.20 - 0.30 |
Structural Variations & Cutting Geometry Logic
The selection of the cut style is as critical as the material itself. We offer four distinct geometries to match specific installation and performance needs:
- • Solid (Un-cut) Rings (T1): Provides the ultimate continuous support. Recommended for high-pressure static applications where the ring can be installed over an open groove without stretching.
- • Scarf-Cut (45° Bias Cut) (T2): The most common design for closed grooves. The angled cut ensures that under pressure, the two ends slide against each other to maintain a continuous support face.
- • Spiral-Cut (Multi-turn) (T3): Features 2 or 3 overlapping turns. This is the premier choice for systems with high thermal expansion, as the overlapping turns compensate for the expansion/contraction of the PTFE matrix.
- • Concave (Curved-Face) Design: Unlike flat rings, our concave back-up rings feature a radius that perfectly matches the O-ring contour. This provides uniform support and prevents the O-ring from deforming into an inefficient "D" shape under high pressure.
Industrial Applications: Where Sealing Failure is Not an Option
- • Oil & Gas Exploration: Crucial for Downhole Drilling Motors, MWD tools, and Packers where pressures exceed 15,000 PSI and temperatures reach +200°C.
- • Aerospace Hydraulics: Flight control surfaces, landing gear, and braking systems where low-temperature flexibility and zero-leakage performance under extreme G-loads are mandatory.
- • Heavy Construction: Hydraulic breakers, excavators, and high-tonnage lifting jacks where pressure spikes are unpredictable and severe, requiring immediate anti-extrusion response.
- • Automotive Precision: High-pressure common rail fuel injection pumps and specialized racing suspension dampers requiring zero stick-slip response.
Technical Q&A & Expert Insights
Q: Can I use a single back-up ring for bi-directional pressure?
A: No. A back-up ring only protects the seal from the side opposite the pressure. If pressure comes from both sides, you MUST install a back-up ring on both sides of the O-ring to ensure complete protection.
Q: How do I install a solid (un-cut) PTFE back-up ring without over-stretching it?
A: For small diameters, we recommend pre-heating the ring in oil at +80°C to +100°C to increase elasticity. Use a conical installation sleeve to slide it, then use a resizing tool to restore its original diameter.
Q: What is the shelf life of a PTFE back-up ring?
A: PTFE is chemically stable and does not age like rubber. The shelf life is virtually unlimited (20+ years) as long as the rings are stored away from direct UV and in a way that prevents mechanical deformation.
Q: Do you support AS568 standard sizing?
A: Yes. We manufacture back-up rings to match all AS568, MS27595, MS28774, and NAS1598 standards, ensuring a perfect fit with all standard industrial and military-spec O-rings.
