Marine Nylon Washers - Electrical Insulation & Vibration Damping
Marine Nylon Washers
Nylon flat washers and insulation washers for marine bolted connections, supplied in PA6 / PA66 / Nylon 610 per ASME B18.22.1 and DIN 125 / DIN 9021. Electrical insulation, vibration damping and gasket sealing for deck equipment, engine room and hull structure from M3 to M64.
What Are Marine Nylon Washers?
Amarine nylon washer is a non-metallic flat disc made from engineering nylon (PA6, PA66 or Nylon 610), placed between a bolt head or nut and the clamped surface. Nylon washers serve three primary functions in marine fastener joints: electrical insulation between dissimilar metals, vibration damping in dynamic connections, and sealing or gasketing against moisture ingress.
Unlike steel washers, nylon washers are non-conductive, chemically resistant to saltwater and most marine fuels, and do not corrode. They are widely used in marine electrical installations, instrumentation mounting, pipe flange gasketing and composite-to-metal transition joints where galvanic isolation is required.
Standards and Types
Nylon washers for marine applications are manufactured to the dimensional specifications of standard metal washers, adapted for non-metallic materials:
| Standard | Type | Outer Diameter | Typical Use |
|---|---|---|---|
| DIN 125A | Plain flat washer | 2× nominal diameter | General load distribution under bolt head |
| DIN 9021 | Large outer diameter flat washer | 3× nominal diameter | Soft material surfaces, wider load spread |
| ASME B18.22.1 | Plain flat washer (inch series) | Per US standard | US Navy and offshore platform spec |
| DIN 127B | Spring washer profile in nylon | Split ring design | Light vibration damping applications |
Nylon Materials Comparison
The choice of nylon material determines the washer's temperature resistance, chemical compatibility and mechanical strength in marine service:
| Material | Continuous Service Temp. | Key Properties | Marine Application |
|---|---|---|---|
| PA6 (Nylon 6) | -40°C to +100°C | Good mechanical strength, absorbs moisture slowly | General purpose marine washers |
| PA66 (Nylon 66) | -40°C to +120°C | Higher stiffness and heat resistance than PA6 | Engine room, higher temperature service |
| Nylon 610 | -40°C to +100°C | Lower moisture absorption, better dimensional stability | Submerged or high humidity applications |
| PA6 + Glass Fiber (30%) | -40°C to +130°C | Higher load capacity, lower elongation | Structural load distribution washers |
Size Range
| Nominal Bolt Size | Washer Inner Diameter | Washer Outer Diameter (DIN 125) | Thickness |
|---|---|---|---|
| M3 - M8 | 3.2mm - 8.4mm | 7mm - 17mm | 0.8mm - 2.0mm |
| M10 - M20 | 10.5mm - 21.0mm | 20mm - 40mm | 2.0mm - 4.0mm |
| M22 - M36 | 23.0mm - 37.0mm | 44mm - 72mm | 4.0mm - 6.0mm |
| M42 - M64 | 45.0mm - 66.0mm | 85mm - 120mm | 6.0mm - 10.0mm |
Custom sizes and dimensions are available for non-standard bolt sizes or specific OEM requirements.
Key Functions in Marine Engineering
Electrical Insulation and Galvanic Isolation
When a steel bolt passes through an aluminum or stainless steel panel, a galvanic cell forms in the presence of saltwater. Nylon washers placed under the bolt head and nut create an electrical barrier that breaks the galvanic circuit, preventing corrosion of the dissimilar metals. This is critical in deck equipment mounting, instrumentation panel installation and composite-to-metal transition joints.
Vibration Damping
Nylon washers absorb vibration energy in bolted joints that are exposed to engine operation, propeller cavitation or wave impact. They reduce stress concentration and prevent fretting fatigue at the clamped interface, extending joint service life.
Sealing and Gasketing
For low-pressure marine piping and water-tight deck penetrations, nylon flat washers act as soft gaskets that compress under bolt preload to form a moisture barrier. They are commonly used in freshwater systems, ballast tank access points and deck hardware where non-metallic sealing is acceptable.
Chemical Resistance
Nylon washers offer good resistance to the following marine and petrochemical environments:
- Seawater and salt spray (continuous exposure)
- Diesel fuel and marine gas oil (MGO)
- Freshwater and brackish water
- Hydraulic oil (mineral-based, up to 80°C)
- Mild alkaline solutions
For strong acid or aromatic hydrocarbon exposure in petrochemical service, PTFE washers per ASTM F468 are recommended instead of nylon.
Quality Control
All marine nylon washers undergo the following inspections before shipment:
- Dimensional inspection per DIN 125 / DIN 9021 / ASME B18.22.1
- Thickness and diameter tolerance verification
- Material identification (IR spectroscopy for PA type confirmation)
- Dielectric strength test (minimum 20 kV/mm per IEC 60243)
- Visual inspection for surface defects and flash
Material test certificates and compliance declarations are supplied with each batch. Third party inspection by DNV, ABS, LR or SGS available on request.
Applications in Marine and Petrochemical Engineering
- Deck equipment: Insulation washers under stainless steel bolts on aluminum deck structures
- Engine room: Vibration damping washers for auxiliary engine mounting bolts
- Hull structure: Gasket washers for watertight door and hatch fasteners
- Electrical installations: Insulating washers for grounding and bonding connections
- Petrochemical tankers: Non-sparking washers for hazardous area instrument mounting
- Composite construction: Load distribution washers for GRP-to-steel bolted joints
Frequently Asked Questions
PA66 has higher stiffness and better heat resistance (up to 120°C vs 100°C for PA6). PA6 absorbs moisture more readily, which slightly reduces its mechanical strength in submerged service but improves its flexibility. For most general marine applications, PA6 is sufficient. For engine room or higher temperature service, specify PA66.
Yes. Nylon washers have a dielectric strength exceeding 20 kV/mm, making them effective electrical insulators. When placed under a bolt head or nut between two different metals (such as steel bolt and aluminum plate), the nylon washer breaks the electrical path and prevents galvanic cell formation in saltwater environments.
Standard nylon washers (PA6/PA66) are rated for continuous service up to 100-120°C. For marine engine exhaust systems, boiler rooms or high temperature petrochemical piping where service temperature exceeds 120°C, use PTFE washers or high temperature mica gaskets instead.
Yes. We supply marine nylon washers from M3 up to M64 (up to 120mm outer diameter) in both DIN 125 and DIN 9021 profiles. Large diameter washers in PA6 + 30% glass fiber are available for structural load distribution applications on deck equipment and hull penetrations.
For marine nylon washer inquiries, contact our engineering team:
Email: sales@sinofastener.com
Website: www.sinofastener.com
