Bonded Seal / Bonded Sealing Washer / Dowty Seal Washer manufacturer & supplier in China
- Payment Way: T/T, Western Union, Paypal
- Incoterm: EXW, FOB, CIF
- Shipping Way: By Air or Sea
- Manufacturer Place: Ningbo, China
- Delivery Time: 7 - 30 days
- Factory Status: Stocked for Sale
Share to SNS:
Savvy maintains an extensive range of standard metric & imperial sizes with ready-made molds for rapid production of Bonded Sealing Washers (Dowty Washers / Dowty Seals). Additionally, we offer comprehensive custom solutions tailored to specialized materials, dimensions, or performance requirements. Whether you need standard or self-centering designs – using common materials like NBR/FKM rubber with carbon/stainless steel, or specialized configurations for extreme environments – our team delivers precision-engineered, reliable sealing solutions.
What are Bonded Sealing Washers?
Bonded Sealing Washers, also known as bonded seals, bonded washers, Dowty seals, and Dowty washers, are specialized sealing washers designed to prevent fluid or gas leaks around a screw or bolt. They consist of an outer rigid metal washer with a vulcanized synthetic rubber ring, bonded concentrically to its inner diameter edge. When installed under the head of a bolt or screw, compression forces the rubber ring to deform radially inward against the thread shaft and outward against the washer. This creates dual sealing barriers: one at the bolt interface and another against the mounting surface, eliminating micro-gaps even under vibration or thermal shifts. Unlike flat gaskets, the metal ring provides structural support that prevents over-compression of the rubber, ensuring consistent sealing force.
Originally developed in the mid-20th century by the Dowty Group in the UK, from which the “Dowty washer” name originates, these seals excel in hydraulic and pneumatic systems such as pumps, valves, or fluid reservoirs. Their key strength lies in reliability under high-pressure rating, capable of handling up to 20,000 PSI. The self-centering design adapts to slight thread misalignments, and the FKM rubber offers resistance to oils, fuels, and a high temperature range. By combining metal’s durability with rubber’s elasticity, bonded sealing washers outperform traditional copper or rubber gaskets, especially in demanding industrial environments.
Bonded Sealing Washer Types
There are mainly two types of bonded seals, differing primarily in their ability to handle misalignment during installation:
1. Standard Bonded Seal (Non Self-Centering):
It is the most widely used bonded seal for all kinds of fittings or nuts. When compressed axially during installation (e.g., under a bolt head or in a threaded port), the rubber deforms radially to create a static seal against the mating surfaces. Its critical limitation is sensitivity to misalignment; it requires precise concentricity between the bolt hole and the sealed bore. If significant eccentricity exists, the rubber compresses unevenly, potentially leading to localized over-compression, premature failure, or leakage. It’s simple and cost-effective, but it demands accurate installation alignment.
2. Self-Centering Bonded Seal:
This type adds a thin layer of rubber that ensures the seal is aligned with the center of the thread, over the standard seal. During axial compression, this allows the rubber ring to radially self-adjust within the washer cavity. This movement automatically compensates for a limited amount of initial misalignment (eccentricity) between the bolt hole and the sealed bore. This tolerance for misalignment makes installation easier and more forgiving of machining variances or assembly tolerances, significantly reducing the risk of leakage due to poor initial centering, especially in applications such as hydraulic fittings that are subject to vibration.
Bonded Seal Washer Materials
Bonded sealing washer consist of two essential parts: Metal for structural support and Rubber for fluid sealing.
The metal provides structural integrity and resistance to compression forces, while the rubber creates the essential fluid-tight seal by deforming under compression. Selecting the right combination of metal and elastomer is critical for optimal performance in specific pressure, temperature, and fluid compatibility environments. Below are the common materials used for each component:
| Metal | Common Grades | Surface Treatment | Key Properties | Typical Applications |
|---|---|---|---|---|
| Carbon Steel | Q235/A36/S235JR | Zinc Plating | High strength, cost-effective | Automotive, general hardware |
| Stainless Steel | 304, 316, 410 | Passivated | Corrosion resistance, durability | Marine, chemical, food |
| Brass | H62/C28000/CW508L | None / Clear Coat | Conductivity, corrosion-resistant | Plumbing, electrical fittings |
| Aluminum | 1060 | Anodized | Lightweight, non-sparking | Aerospace, lightweight assemblies |
| Rubber | Temp. Range (°C) | Colors | Key Properties | Common Applications |
|---|---|---|---|---|
| NBR | -30 to +110 | Black | Excellent oil/fuel resistance | Hydraulics, fuel systems |
| FKM/Viton | -20 to +200 | Brown | High heat/chemical resistance | Aerospace, chemical seals |
| EPDM | -50 to +150 | Black | Weather/ozone/steam resistant | Automotive cooling, outdoor |
| VMQ | -60 to +225 | Red | Flexible at temps, non-reactive | Medical, food-grade seals |
Other special rubber elastomers are available, such as neoprene, HNBR, and FFKM; however, neoprene bonded washers and FFKM bonded washers are seldom used. Contact our sales team to know more!
Bonded Sealing Washer Standard Sizes
According to the thread specifications of different countries, there are major imperial & metric bonded sealing washer standard sizes, including the China JB982-77 standard, the Imperial BSP USA/UK standard, the German/French ISO R261 BS 3643 metric standard, and the specialized CEPOTES (ISO 1179-1973) standard.
These standards are critical for selecting seals that precisely match thread geometries, pressure ratings, and application demands.
We list them to guide your product integration.
Bonded Sealing Washer Advantages
Bonded Sealing Washer provide critical operational advantages in demanding environments, including:
- Excellent leak-proof sealing for fluids under high pressure.
- Metal rings prevent rubber over-compression, ensuring longer seal life.
- Eliminate assembly gaps by filling irregularities between mating surfaces to ensure a secure fit.
- Withstand extreme temperatures and pressures reliably in harsh environments.
- Reduce required bolt torque, simplifying installation and lowering stress.
Bonded Sealing Washer Applications
Bonded sealing washer are critical for reliable static sealing in high-pressure fluid systems where space is limited. They are extensively used in hydraulic and pneumatic equipment, including sealing components such as cylinders, pumps, valves (cartridge, solenoid, and control), manifolds, and fittings. In the automotive and heavy machinery industries, they secure fuel injectors, engine covers, transmission housings, power steering units, and fluid lines. Beyond mobile equipment, bonded seals serve in compressors, refrigeration systems, chemical processing plants, and precision instrumentation.
Their robustness makes them ideal for demanding environments in construction, agriculture, mining, marine, and offshore oil & gas operations. These seals effectively prevent leaks of oil, fuel, water, air, and hydraulic fluids at threaded ports, plugs, adapters, and flange connections, even under extreme pressures and temperature fluctuations. Essentially, bonded seals offer vibration-resistant, space-efficient sealing for bolted or threaded metal-to-metal joints across various industries, including aerospace, manufacturing, and energy.