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High Pressure Dowty Bonded Seal US USS Bonded Washer for Hydraulic Fittings
Category：Bonded Seal, Dowty Seal
Temperature: -20℃~+200℃
Material: FKM+SS316
Color: Brown
Product description: Bonded seal, also known as Dowty seal or bonded washer, is a one-piece static face seal made by vulcanizing rubber onto a metal washer. It features controlled compression design, metal ring acts as hard stop to prevent rubber over-compression and extrusion.
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1. Product Overview
A bonded seal, also widely known as Dowty seal or bonded washer, is a high-performance one-piece static sealing component. It is integrally molded by vulcanizing elastic rubber and a metal washer, featuring a controlled compression structure. This product is specially designed for face sealing of threaded ports and plug joints, widely used in hydraulic and pneumatic systems. It effectively solves leakage problems caused by uneven assembly, excessive tightening torque and vibration, serving as an ideal replacement for traditional copper gaskets and ordinary O-rings.
2. Product Types & Structure
We provide two mainstream types to meet diverse installation requirements:
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US Standard Type: Flat metal washer with inner vulcanized rubber sealing lip, compact structure, suitable for standard installation scenarios with accurate positioning.
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USS Self-centering Type: Equipped with a positioning boss on the rubber inner hole, which can automatically align with bolts during installation to avoid offset and falling off. It is the most popular type for hydraulic equipment assembly.
Structural Features: The rubber lip is slightly higher than the metal surface. During tightening, the rubber is compressed first to fit the sealing surface tightly, while the metal ring acts as a hard limit to prevent over-compression and rubber extrusion damage, ensuring stable and controllable sealing compression.
3. Standard Materials & Working Parameters
Elastomer Sealing Material
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NBR : Temperature range: -30℃ ~ +120℃. Excellent resistance to mineral hydraulic oil, lubricating oil and fuel. It is the most cost-effective and universal material for conventional industrial equipment.
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FKM : Temperature range: -20℃ ~ +200℃. Superior high temperature resistance and chemical corrosion resistance, suitable for high-temperature environments and synthetic hydraulic oil media.
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EPDM : Temperature range: -40℃ to +150℃. Perfect for water, steam and glycol aqueous solution systems, widely used in waterway and cooling system sealing.
Metal Washer Material
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Carbon steel with galvanized/phosphated treatment: Low cost, good anti-rust performance, for general industrial working conditions.
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304/316 stainless steel: High corrosion and rust resistance, applicable to marine, chemical and humid harsh environments.
Pressure Resistance
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Counterbore installation: Maximum working pressure up to 1000 bar
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Non-counterbore installation: 250 bar (outer diameter ≤40mm); 400 bar (outer diameter ＞40mm)
4. Core Advantages
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Ultra-high Sealing Stability: Adopts pressure self-tightening principle — the higher the system pressure, the tighter the rubber lip fits the surface, achieving zero leakage for long-term operation.
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Anti-vibration & Anti-loosening: Integrated metal-rubber structure resists equipment vibration, avoiding leakage caused by loose sealing.
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Installation & Cost Saving: No need for reserved O-ring grooves, simplifies processing and assembly procedures, saves installation space and production cost.
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Over-tightening Protection: Metal limit structure prevents rubber crushing and failure caused by excessive bolt torque.
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Complete Size Coverage: Supports metric thread, BSPP/G British pipe thread and other international standard sizes, compatible with most mainstream equipment.
5. Wide Applications
Widely used in static face sealing of various hydraulic and pneumatic equipment, including hydraulic valve blocks, oil port plugs, banjo fittings, hydraulic pumps, motors, gearboxes, pressure sensors, construction machinery, automotive hydraulic systems, aerospace hydraulic equipment and pressure vessels. It is a universal sealing part for industrial mechanical fluid systems.
6. Installation & Usage Notes
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Belongs to static sealing parts only, not applicable for rotating or reciprocating dynamic sealing scenarios.
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Recommended to replace a new gasket after each disassembly. Repeated use will cause permanent deformation of rubber and lead to leakage.
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The sealing mounting surface requires a roughness of Ra ≤3.2μm without scratches, burrs or impurities.
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Control the tightening torque strictly to avoid excessive compression damage to the rubber lip.
7. Executive Standards
Compliant with international and industrial mainstream standards: JB982-77 Chinese national standard, Freudenberg Dichtomatik US/USS series standard, fully matching global standard mechanical assembly specifications.
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