Performance and Technical Parameters
| Performance Indicator | Value / Range | Description |
|---|---|---|
| Operating Temperature Range | -60 °C to +250 °C (continuous); +300 °C (short-term) | Retains mechanical strength across a wider working range than PTFE, ideal for hot oil, steam and superheated media |
| Pressure Load Capacity | ≤ 175 MPa (long-term); ≤ 200 MPa (peak) | When paired with a primary seal, raises the pressure ceiling of standard O-rings from ~10 MPa to over 50 MPa |
| Hardness | Shore D 88–92 | Provides rigidity to bridge extrusion gaps while retaining installability |
| Anti-Extrusion Gap | ≤ 0.20 mm @ 20 MPa ≤ 0.15 mm @ 50 MPa ≤ 0.10 mm @ 100 MPa |
Optimized to prevent O-ring cold-flow into clearance gaps |
| Radial Wall Thickness | 0.8–3.0 mm | Customized to groove geometry; standard configurations 1.5–2.0 mm |
| Cross-Section Tolerance | ± 0.05 mm | Ensures precision fit and repeatable assembly |
| Surface Roughness | Ra ≤ 0.8 μm (sealing face) Ra ≤ 1.6 μm (non-working face) |
Reduces friction and prolongs service life |
| Friction Coefficient | 0.10–0.15 (dry) 0.05–0.08 (lubricated) |
Inherent self-lubrication reduces breakaway and running resistance |
| Chemical Resistance | Strong acids, strong alkalis, organic solvents, H₂S, CO₂ | Limited only by concentrated H₂SO₄ and HNO₃ at elevated temperatures |
| Anti-Creep (Cold Flow) | ≥ 5 × better than PTFE | Creep rate < 0.5 % vs. PTFE 3–5 %; dimensionally stable under sustained load |
| Key Mechanical Properties | Tensile ≥ 100 MPa Flexural ≥ 165 MPa Tg = 143 °C |
Retains > 80 % tensile strength at 200 °C |
Typical Application Fields
Oil & Gas Exploration and Transportation
Downhole packers, wellhead assemblies, high-pressure manifolds — preventing O-ring extrusion failure under formation pressures ≥ 50 MPa, and resisting sour-service environments containing H₂S / CO₂.
Hydraulic and Pneumatic Systems
Piston and rod seals in heavy-duty hydraulic cylinders (≥ 25 MPa) for construction equipment, injection molding machines, and hydraulic presses; aerospace hydraulic circuits (≥ 35 MPa, -54 °C to +200 °C).
Chemical Pumps and Valves
Shaft seals and mechanical seal support in multistage centrifugal pumps and plunger pumps; anti-extrusion protection for ball valve and gate valve seats handling caustic and chlor-alkali media.
Semiconductor & Pharmaceutical
Ultra-pure media transfer systems (electronic-grade chemicals, WFI); FDA-compliant and USP Class VI grades available with no leachable contamination.
Automotive and Aerospace
Common-rail fuel injection pumps (≥ 200 MPa), transmission hydraulics; aircraft engine fuel and hydraulic sealing under extreme thermal cycling and vibration.
Have a Specific Application in Mind?
Share your operating conditions and requirements with us. Connect with our application engineers for a custom-engineered PEEK sealing solution.
Common Failure Modes and Remedies
Primary Seal Extrusion or Nibbling
CAUSES
- Insufficient wall thickness
- Excessive extrusion gap
- System over-pressure
REMEDIES
- Increase ring cross-section by 0.3–0.5 mm
- Reduce extrusion gap to ≤ 0.15 mm
- Switch to twin-ring configuration for > 70 MPa
Backup Ring Cracking or Fracture
CAUSES
- Excessive installation stress
- Brittle material grade selection
- Severe thermal shock
REMEDIES
- Use chamfered installation tooling
- Select toughened / GF-reinforced PEEK
- Preheat ring to 60–80 °C before assembly
Persistent Leakage
CAUSES
- Dimensional deviation (out of tolerance)
- Damaged primary seal (O-ring)
- Rough hardware groove
REMEDIES
- Verify inner Ø H9 / outer Ø h8 tolerances
- Replace O-ring simultaneously
- Regrind groove to Ra ≤ 0.8 μm
Installation Difficulty or Jamming
CAUSES
- Excessive hardness of the ring
- Oversized cross-section
- Low ambient temperature during assembly
REMEDIES
- Use dedicated expansion tooling
- Apply silicone or media-compatible lubricant
- Warm to room temperature when ambient < 10 °C
Media Incompatibility
CAUSES
- Media outside compatibility envelope
- Maximum operating temperature exceeded
REMEDIES
- Cross-check PEEK chemical compatibility chart
- Upgrade to PI or modified PEEK for > 250 °C
- Use PTFE or metal for > 90% H₂SO₄
Essential Information for Procurement Engineers
- System Parameters: Maximum / normal operating pressure (MPa), temperature range (°C), media type & concentration, static vs. dynamic sealing.
- Seal Groove Dimensions: Inner diameter $D_1$, outer diameter $D_2$, groove depth $H$, extrusion clearance $\delta$ (mm; engineering drawing preferred).
- Primary Seal Specification: O-ring standard (GB, JIS, AS568…), cross-section diameter, elastomer material (NBR / FKM / FFKM).
- Service Characteristics: Stroke frequency & speed (dynamic), pressure pulsation, media viscosity, solid-particle content.
- Ring Cross-Section: Recommended clearance $\delta \le 0.02 \cdot P + 0.03$ (where $P$ = MPa); single or twin-ring configuration.
- Material Grade: Pure PEEK (≤ 25 MPa); 30% glass-fiber PEEK (25–70 MPa); 30% carbon-fiber PEEK (> 70 MPa or wear-intensive service).
- Tolerance Grade: Precision grooves H7/h6; standard grooves H9/h8; ring cross-section ± 0.05 mm.
- Surface Treatment: Optional low-friction coating or edge chamfering for easier installation.
Have Your Technical Data Ready?
Submit your system parameters, groove dimensions, or engineering drawings directly to our sales engineers for a rapid quotation and technical feasibility review.
Frequently Asked Questions (FAQ)
Q1: What advantages do PEEK backup rings offer over PTFE backup rings?
- Stronger anti-extrusion: Shore D 88 (PEEK) vs. Shore D 50–65 (PTFE), resulting in far less deformation under high pressure.
- Excellent cold-flow resistance: PEEK creep rate < 0.5% vs. PTFE 3–5%, remaining dimensionally stable under sustained load.
- Superior high-temperature strength: PEEK retains > 80% tensile strength at 200 °C, whereas PTFE loses significant strength above 150 °C.
- Broader chemical resistance: PEEK safely handles strong alkalis (e.g., 50% NaOH) and amines that typically degrade certain PTFE compounds.
Q2: How do I size a PEEK backup ring cross-section?
The radial wall thickness $h$ should be at least 1.5–2 × the extrusion gap $\delta$, and no more than 70% of groove depth to avoid over-preloading.
The axial width $t$ should be 0.4–0.8 × the O-ring cross-section diameter $w$ ($0.6w$ is recommended).
Example: For an O-ring Ø 3.55 mm (JIS P5), with $\delta = 0.15$ mm operating at 40 MPa, the recommended values are $h \approx 0.8$ mm (minimum standard) and $t \approx 2.1$ mm.
Q3: When should I choose single vs. twin backup rings?
- Single ring: Recommended for ≤ 50 MPa, unidirectional pressure, or cost-sensitive applications.
- Twin rings: Required for > 50 MPa, bidirectional pressure (reciprocating service), or extreme conditions (particulate media). Note: Twin-ring grooves require additional width plus 0.3–0.5 mm inter-ring clearance to prevent jamming.
Q4: Is there an installation orientation requirement?
For split rings (spiral cut), the opening should face away from the pressure source, offset by 30–45°, to prevent high-pressure media from directly attacking the split. Solid closed rings have no orientation requirement but require an expansion mandrel and sizing tool for installation.
Q5: When should a PEEK backup ring be replaced?
A replacement is necessary if you observe any of the following:
- The primary seal shows repeat leakage or extrusion damage.
- Cracks, chips, or visible plastic deformation appear on the ring.
- The ring-to-groove fit has become noticeably loose (hand-removable).
- System pressure has been up-rated > 20% above the original design.
Best Practice: Replace concurrently with the primary seal. Preventive replacement interval is typically 1.5–2 × the primary seal’s service life.
Q6: Can PEEK backup rings be used with particulate media?
They are suitable for light abrasive service (particle size < 50 μm, content < 5%); 30% carbon-fiber reinforced PEEK is recommended here for improved wear resistance. For heavy abrasive service (e.g., mud pumps, heavy slurry pumps), metallic or ceramic-coated backup rings are advised, as PEEK is susceptible to scoring by large, hard particulates.
Q7: How do PEEK backup rings perform at low temperatures (e.g., -40 °C)?
PEEK maintains excellent toughness and dimensional stability down to -60 °C. (For deep-cryogenic service < -100 °C, PTFE remains the material of choice). Low-temperature best practices include:
- Warm the rings to room temperature before installation to prevent brittle fracture.
- Expect a 15–25% increase in dynamic breakaway friction; allow adequate torque margin.
- Use low-temperature-rated lubricants (e.g., PFPE) to reduce cold-start wear.
Q8: How can I verify PEEK backup ring quality?
Always request the following documentation from your supplier:
- Material Certificate: Check for density 1.30 ± 0.02 g/cm³, melting point 343 ± 3 °C, hardness Shore D 88–92.
- Dimensional Inspection Report: Verify standard tolerances (e.g., ± 0.05 mm) and surface finish (Ra ≤ 0.8 μm).
- Pressure Test Data: Ensure no leakage after a 72-hour hold at rated pressure and temperature.
- DSC Thermal Analysis: For critical applications, request a DSC curve to confirm authentic PEEK resin is used, rather than PPS or lower-cost substitutes.
About Dalian Allstar Material
Dalian Allstar Material is a Chinese national high-tech enterprise dedicated to the R&D, manufacturing, and technical service of high-performance engineering polymers, including PEEK (polyetheretherketone) and PI (polyimide).
With in-house polymerization and compounding capability, precision CNC machining centers (± 0.03 mm), and a full performance-testing laboratory, we deliver end-to-end solutions from material selection and structural design to serial production. Our products serve 500+ customers across petrochemical, aerospace, semiconductor, and medical device industries, with exports to 30+ countries including Europe, North America, the Middle East, and Southeast Asia.