RFQ Today
Certifications available: EN 10204 3.1 / 3.2 MTRs, ASTM F844 / ISO 7093 compliance, passivation per ASTM A967 for SS grades, Third-Party Inspection available, and complete export documentation packages.
Fender
Washers
A world-class technical reference for EPC contractors, structural and mechanical engineers, procurement heads, and global project buyers specifying fender washers — thin, large-OD flat washers designed to distribute bolt bearing load across soft, thin, fragile, or flexible connected materials including rubber sheeting, neoprene isolation pads, GRP panels, polycarbonate roofing, thin sheet metal, elastomeric bearings, and acoustic isolation mounts — preventing pull-through, crushing, and localised perforation failures under bolt preload.
Type Classification
& Pull-Through Prevention
Fender washers are thin, large-OD flat washers — characterised by an OD-to-thickness ratio significantly greater than standard plain washers — designed specifically to distribute bolt bearing load across the maximum possible area on soft, fragile, or compressible connected materials where a standard washer OD would cause pull-through, crushing, or material perforation.
1.1 — Technical Definition and Scope
A fender washer is defined by its geometry: a thin flat washer with an outside diameter substantially larger than a standard plain washer for the same bolt hole — typically an OD-to-ID ratio of 4:1 to 8:1, and an OD-to-thickness ratio of 15:1 to 40:1. These proportions distinguish fender washers from dock washers (which are thick and structural) and from standard plain washers (which have OD-to-thickness ratios of approximately 5:1 to 8:1). The thin profile is essential for applications where the connected assembly has limited clearance or where the flexibility of the washer is beneficial — a thin fender washer will deflect elastically under the bolt bearing force, conforming to minor surface irregularities and distributing the contact stress more uniformly than a rigid thick washer.
The term “fender washer” has a dual etymology: (1) from the automotive and body shop context, where they were historically used to attach rubber fender trim and mudguard panels to thin sheet metal car bodies without pulling through; and (2) from the marine context, where large thin washers are used in rubber dock fender attachment bolts — distributing the bolt bearing load across the rubber face of the fender without tearing through the rubber. Both etymologies share the same engineering function: maximum area load distribution through a thin, wide washer profile on compliant or fragile surfaces.
1.2 — Fender Washer Type Classification
Standard Metal Fender Washer (Steel / SS)
A thin flat circular washer stamped from carbon steel coil (ASTM A36, typically 1.5–3 mm thick) with a large OD — typically 3–6× the bolt nominal diameter. Used across sheet metal, thin composite panels, rubber, neoprene, and light structural applications where the large OD prevents bolt pull-through. Available in zinc-plated, hot-dip galvanised, and SS 316 variants. Per ASME B18.22.1 Type A extra-large series (inch) and ISO 7093 large series (metric). The most common washer type for light construction and manufactured product assembly where a large bearing area is required without the weight or cost of a thick dock washer.
Rubber-Faced Fender Washer (Bonded Composite)
A steel fender washer with a vulcanised neoprene or EPDM rubber face bonded to one side — combines the large bearing area of a metal fender washer with a resilient, waterproof sealing face. The rubber face: (1) seals around the bolt hole in the connected material (GRP panel, polycarbonate sheet, corrugated roofing) preventing water ingress at the fastening point; (2) distributes the bolt bearing load with improved conformity over surface irregularities; and (3) provides vibration isolation between the bolt head and the connected panel. Standard rubber-faced fender washers: rubber shore hardness 40–60 Shore A; bonded to 2–3 mm steel substrate; OD typically 25–50 mm for M6–M12 roofing and cladding bolts.
EPDM / Neoprene Isolation Washer
A solid rubber (EPDM or neoprene) flat washer — no metal substrate — used as an isolation and sealing element at bolt connections through roofing sheets, cladding panels, GRP, and polycarbonate. EPDM isolation washers provide: UV resistance (EPDM retains elasticity after 20+ years of outdoor UV exposure where neoprene degrades after 5–10 years); temperature resistance (EPDM service range −40°C to +120°C); excellent weatherseal at the bolt hole; and vibration isolation. Used as a set with a metal fender washer on top — the metal washer bridges the rubber deformation and provides a flat bearing surface for the bolt head, while the rubber below provides the seal and isolation.
PTFE / Polymer Fender Washer
A flat washer moulded or machined from PTFE (polytetrafluoroethylene), nylon 66, acetal (Delrin), or UHMWPE — used where: (1) electrical insulation between the bolt and the connected material is required (isolating electrical equipment panels, EMC-shielded enclosures); (2) metal contamination of the connected material must be prevented (pharmaceutical equipment, food processing plant); (3) chemical resistance to aggressive fluids is required (acids, alkalis, solvents); or (4) the lowest possible friction coefficient is needed at the washer-material interface (sliding bearing pads, expansion connections). PTFE fender washers are self-lubricating and have very low μ (0.04–0.08) — they provide excellent slip resistance in applications subject to thermal expansion movement.
Bonded Metal-Rubber (EDPM-Steel) Roofing Washer
A precision-engineered roofing and cladding fastener washer — the industry-standard fastening element for through-fastened metal roofing, standing seam roofing, and polycarbonate rooflights. The metal substrate (1.5–2 mm carbon steel or SS 316 with zinc-flake or Galfan coating) provides the structural bearing area; the bonded EPDM rubber sealing layer (3–5 mm thick, Shore A 50–60) creates the weathertight seal around the fastener hole. The EPDM layer is dimensioned to compress 30–40% under the fastener tightening torque — providing a pre-loaded seal that resists water ingress at the fastener point under wind uplift and thermal movement. Available with or without a top metal retaining cap to protect the rubber from UV and mechanical damage.
Vibration Isolation Washer (Anti-Vibration)
A moulded rubber or rubber-metal bonded washer specifically designed to attenuate vibration transmission between a vibrating machine or panel and its structural support. The rubber element acts as a spring in the bolt-joint load path — absorbing vibration energy from the connected panel or equipment and preventing transmission to the building structure or supporting frame. Vibration isolation washers are specified by their natural frequency (typically 5–20 Hz for general machinery isolation) and static deflection (2–15 mm under bolt preload). Used in: HVAC duct connection bolts, electrical transformer mounting bolts, compressor inspection cover bolts, and marine engine hatch cover connections where acoustic and vibration isolation are required alongside weather sealing.
1.3 — Pull-Through Prevention and Bearing Stress Engineering
σ_allow = Allowable bearing stress of connected material (MPa) — see table below
A_net = Net washer bearing area (mm²) = π/4 × (OD² − ID²)
F_bolt = Bolt clamping force at installation (N) — from bolt grade and installation torque
Min OD = Minimum washer OD to prevent pull-through (mm)
ID = Washer hole diameter (mm) ≈ bolt nominal diameter + 1 mm clearance
Allowable bearing stress (σ_allow) for common fender washer applications:
Rubber sheet (Shore A 60): σ_allow = 0.5–1.5 MPa (under static bolt load)
Neoprene pad: σ_allow = 1.0–3.0 MPa
Polycarbonate sheet (6 mm): σ_allow = 10–15 MPa (bearing perpendicular to sheet)
GRP (glass reinforced polyester, 5 mm): σ_allow = 20–40 MPa
Thin steel sheet (1.5 mm, S235): σ_allow = 250 MPa (pull-through governed by shear of sheet)
Min OD = √(4 × 8,000 / (π × 30) + 9²) = √(339 + 81) = √420 = 20.5 mm
Standard ISO 7093 M8 large-series OD = 25 mm → A_net = π/4 × (25² − 9²) = 427 mm²
σ_bearing = 8,000 / 427 = 18.7 MPa < 30 MPa allowable → ISO 7093 large series adequate
For rubber neoprene pad at σ_allow = 2 MPa: Min OD = √(4×8,000/(π×2) + 9²) = 72.4 mm → fender washer required
1.4 — Standard vs Fender Washer: Geometry and Application Selection
| Connected Material | σ_allow (MPa) | Standard Washer Adequate? | Fender Washer Recommended | Min OD for M10 (F=14 kN) |
|---|---|---|---|---|
| Structural steel (A36) | 225 | Yes — standard ISO 7089 | No | 10.5 mm (bolt diameter sufficient) |
| Concrete / masonry | 15–25 | Marginal | Yes — large OD plate | 28–36 mm |
| GRP / fibreglass (5 mm) | 20–40 | Large series (ISO 7093) | Yes for thin GRP | 22–31 mm |
| Polycarbonate (6 mm) | 10–15 | No — pull-through risk | Yes | 34–42 mm |
| Timber (softwood) | 3–5 | No | Yes — dock or fender | 60–78 mm |
| Neoprene pad (10 mm) | 1.5–3 | No | Yes — large fender | 78–111 mm |
| Rubber sheet (5 mm) | 0.5–1.5 | No | Yes — very large OD | 109–189 mm |
| Corrugated steel (0.7 mm) | Governed by shear pull-through | No | Yes — roofing washer | 25–32 mm (bond pattern) |
| Aluminium extrusion (3 mm) | 80–120 | Large series adequate | Often yes | 14–17 mm (large series OK) |
Submit your bolt size, OD, thickness, material, facing type, and quantity for a documented RFQ within 24 hours.
Size Reference Tables
& Compliance Framework
Fender washer dimensions are governed by ASME B18.22.1 Type A extra-large (inch), ISO 7093 large series (metric), DIN 9021, and manufacturer’s dimensional tables for rubber-faced and specialist variants. All applicable standards are supported at RR Hydraulic.
Submit bolt size, OD, thickness, material, coating, and quantity to sales@rrhydraulics.com for a certified offer.
2.1 — ISO 7093 Large-Series Fender Washer Dimensional Reference
| Bolt Size | Hole Dia (mm) | ISO 7093 OD (mm) | Thickness ISO 7093 (mm) | Extended Fender OD (mm) | Extended Thickness (mm) | Bearing Area ISO 7093 (mm²) |
|---|---|---|---|---|---|---|
| M4 | 4.5 | 12 | 1.0 | 20 | 1.5 | 97 |
| M5 | 5.5 | 15 | 1.2 | 25 | 1.5 | 152 |
| M6 | 6.6 | 18 | 1.6 | 30 | 2.0 | 219 |
| M8 | 9.0 | 25 | 2.0 | 38 | 2.5 | 428 |
| M10 | 11.0 | 30 | 2.5 | 50 | 3.0 | 612 |
| M12 | 13.5 | 37 | 3.0 | 60 | 3.0 | 932 |
| M14 | 15.5 | 44 | 3.0 | 75 | 3.0 | 1333 |
| M16 | 17.5 | 50 | 4.0 | 80 | 3.5 | 1720 |
| M20 | 22.0 | 60 | 4.0 | 100 | 4.0 | 2443 |
| M24 | 26.0 | 72 | 5.0 | 120 | 5.0 | 3539 |
2.2 — Applicable Standards and Compliance Framework
ISO 7093 / DIN 9021
ISO 7093: Plain washers — large series, product grade A. Defines OD, ID (hole diameter), and thickness for M4–M36 metric fender-type large-series washers. DIN 9021 is the German equivalent and is dimensionally consistent with ISO 7093. The ISO 7093 large series provides OD approximately 3× the bolt diameter — substantially wider than ISO 7089 normal series (OD ≈ 2× bolt diameter) but not as wide as custom extended fender washers. For applications requiring OD greater than ISO 7093 range: specify by project drawing with material and coating reference. All RR Hydraulic fender washers are supplied to ISO 7093 or project drawing dimensions with EN 10204 3.1 material certification.
ASME B18.22.1
Plain Washers (Inch Series) — Type A extra-large series provides OD approximately 3–4× the bolt diameter: the US equivalent of ISO 7093 for inch-series fasteners. Used on US-coded EPC projects and manufactured products with inch-series bolt patterns. ASME B18.22.1 Type A narrow (standard), Type B regular, and Type A extra-large series cover the full range from standard washers through fender washers. For metric bolts on US projects: specify ISO 7093 dimensions but reference ASTM F844 for material grade (unhardened plain steel washer) or ASTM A276 Type 316 for SS material.
ASTM F844
Standard Specification for Washers, Steel, Plain (Flat), Unhardened, for General Use. The US material standard for fender washers in carbon steel — covers unhardened plain flat washers without specifying OD or ID (those are governed by ASME B18.22.1 or project drawing). ASTM F844 requires ASTM A36 or ASTM A108 material. For marine and outdoor fender washers: specify F844 material with hot-dip galvanising per ASTM A153 Class A, or zinc-flake coating per ISO 10683. For SS fender washers: reference ASTM A276 Type 316L (SS 316L bar/sheet) as the material standard.
ISO 9227 / ASTM B117
Salt spray testing for corrosion qualification of coated fender washers. Zinc-plated fender washers: minimum 200 hours salt spray per ISO 9227 without red rust (ASTM B633 Class Fe/Zn8). Hot-dip galvanised: minimum 1000 hours. SS 316 passivated: minimum 1000 hours. Rubber-faced and EPDM-bonded fender washers: metal substrate tested to applicable standard; rubber bonding integrity verified by peel test (minimum 4 N/mm bond strength per EN 12232 adhesion test). Salt spray certificates on production lots for offshore and marine atmospheric applications.
EN 1090 / AISC 360
EN 1090-2 (Execution of Steel Structures) and AISC Specification Chapter J govern structural steel connections including washer requirements. EN 1090-2 Clause 8.3 requires washers under bolt heads and nuts for structural connections; large-series (ISO 7093 / DIN 9021) washers are specified where the connected material bearing strength is lower than the standard series bearing capacity. For EN 1090 CE-marked structural connections: the washer must be CE-marked under EN 14399 (preloaded connections) or EN 15048 (non-preloaded connections) — plain fender washers in structural connections must be specified to the appropriate EN standard as part of the bolt assembly system.
ETAG 006 / ETA — Roofing
ETAG 006 (European Technical Approval Guidelines for Roof and Wall Cladding Fasteners) and national building codes govern the specification of roofing and cladding fasteners including the washer component. Roofing fender washers (metal-backed EPDM roofing washers) used in through-fastened roof systems must comply with the pull-through and pull-out test requirements of the relevant ETA (European Technical Assessment) for the roof fastener system. For certified roofing systems: use only fender washers that are part of a tested and ETA-approved roofing fastener system — mixing uncertified fender washers into a CE-marked roofing fastener system invalidates the system certification.
ISO 1461 / ASTM A153
Hot-dip galvanising standards for carbon steel fender washers. ISO 1461 minimum average coating: 45 µm for material thickness 1.5–3 mm (standard fender washer thickness). ASTM A153 Class B (material 1.6–4.8 mm): 0.9 oz/ft² minimum (274 g/m², approximately 38 µm). For thin fender washers (below 1.5 mm): ISO 1461 applies Class C (minimum 35 µm). HDG fender washers must be jigged individually in the zinc bath — stacked washers in contact with each other receive no zinc on the contact faces, leaving bare steel patches that corrode immediately after installation.
ASTM C719 / ISO 11600
ASTM C719 (Joint Movement Capability and Adhesion of Sealants) and ISO 11600 (Building Construction — Jointing Products — Classification and Requirements for Sealants) — referenced when EPDM or neoprene-faced fender washers are used as part of a weathertight connection system in façade, roofing, and glazing applications. The rubber facing of the fender washer is the sealing element at the fastener hole — it must maintain adhesion to both the metal substrate and the connected panel face under thermal cycling (−40°C to +80°C) and UV exposure over the product design life (25+ years for commercial roofing). EPDM bonding integrity and compression set resistance are the key qualification tests.
Rubber Bonding
& Surface Treatment
Fender washer material selection is driven by the service environment, the connected panel material, and any sealing or isolation requirement. RR Hydraulic supplies fender washers in all standard grades — carbon steel, hot-dip galvanised, zinc-flake, SS 316, and rubber-faced bonded composite variants — with full EN 10204 3.1 traceability.
3.1 — Material and Coating Reference
| Material / Coating | Thickness Range | Marine Atm. | UV Resistance | Chemical Resistance | Sealing | Typical Application |
|---|---|---|---|---|---|---|
| A36 — Zinc-Plated | 1.5–3 mm | Poor | N/A | Poor | No | Indoor light construction; general hardware |
| A36 — Hot-Dip Galvanised | 1.5–3 mm | Good | N/A | Moderate | No | Outdoor structural; timber; marine atmospheric |
| A36 — Zinc-Flake (Geomet) | 1.5–3 mm | Very Good | N/A | Good | No | Industrial; machinery; EPC equipment |
| SS 316 — Passivated | 1.5–3 mm | Excellent | N/A | Very Good | No | Offshore; marine; chemical; food/pharma |
| Metal + EPDM Bonded | 2 mm steel + 3 mm rubber | Excellent | Excellent | Good | Yes | Metal roofing; polycarbonate; GRP cladding |
| Metal + Neoprene Bonded | 2 mm steel + 3 mm rubber | Good | Fair (degrades) | Very Good | Yes | Industrial cladding; rubber dock fenders |
| EPDM Solid Rubber | 3–6 mm | Excellent | Excellent | Good | Yes | Rooflight bolts; isolation; acoustic sealing |
| PTFE | 1–3 mm | Excellent | Excellent | Excellent | Partial | Chemical plant; electrical isolation; sliding |
| Nylon 66 / Acetal | 1.5–3 mm | Good | Fair | Good | No | Electrical isolation; lightweight; non-magnetic |
3.2 — Manufacturing Process
3.2.1 — Stamping and Punching (Metal Fender Washers)
Standard metal fender washers are stamped from coil stock on progressive die press tooling — the OD is blanked and the hole is punched simultaneously in a single press stroke. Coil material: cold-rolled steel (CR4 / SPCC) for zinc-plated; hot-rolled pickled and oiled (HRPO / SPHC) for galvanised; SS 316 coil for marine-grade SS washers. The stamped edge (OD and ID) has a shear zone and rollover — acceptable for all light and medium applications. For SS 316 fender washers: passivation per ASTM A967 removes any iron contamination from the stamping die or handling equipment before dispatch. Hole punching tolerance: hole diameter +0.3/+0.8 mm — clearance fit adequate for fender washer applications where precise hole location is not critical.
3.2.2 — Rubber-to-Metal Bonding (Composite Fender Washers)
- Surface preparation: Metal substrate shot-blasted to Sa 2.5 (ISO 8501-1) for maximum surface area; primed with bonding agent (Chemlok 220 or equivalent vulcanisation bonding primer) applied to the clean metal face before rubber moulding
- Moulding: EPDM or neoprene rubber compound moulded directly onto the metal substrate under heat and pressure in a closed mould — vulcanisation bonds the rubber chemically to the primed metal face; mould temperature 150–180°C, mould time 5–20 minutes depending on rubber compound and thickness
- Bond strength verification: Peel test per ISO 813 (180° peel) on production samples: minimum bond strength 5 N/mm for EPDM-to-galvanised steel; 4 N/mm for neoprene-to-zinc plate; 6 N/mm for EPDM-to-SS 316 (higher surface energy primer). Bond failure must be cohesive (rubber tears, not adhesive — metal surface remains covered with rubber); adhesive failure (rubber peels cleanly from metal) indicates surface preparation or primer failure
- Compression set testing: EPDM and neoprene rubber compound compression set per ISO 815: maximum 25% set after 70 hours at 70°C — ensures the rubber retains sealing performance after prolonged bolt preload and thermal cycling
- EPDM vs neoprene selection: EPDM for exposed outdoor and marine environments (superior UV, ozone, and weathering resistance); neoprene for chemical environments and oil-adjacent service (neoprene has better resistance to petroleum-based oils than EPDM); neoprene for lower-temperature service (EPDM rated to −40°C; neoprene rated to −20°C standard grade)
Industry Applications
& Documentation
RR Hydraulic maintains full traceability from certified coil or sheet stock to final coated, bonded, and packed fender washer shipment. Dimensional inspection, coating thickness, bond strength testing (rubber-faced), passivation, and complete project documentation packages are standard on all project-grade fender washer supply.
4.1 — Inspection & QC Protocol
4.2 — EN 10204 Material Test Certificate Requirements
| Certificate | Content | EPC / Construction Requirement | When Mandatory |
|---|---|---|---|
| 2.1 / 2.2 | Declaration / non-specific | Minimal — general hardware | Acceptable only for non-critical general hardware; not for EPC structural |
| 3.1 | Coil/sheet heat-traceable mech + chem | Standard for EPC fender washers | All structural, marine, offshore, and roofing system fender washers |
| 3.2 | 3.1 + TPI countersign | Offshore; marine critical; nuclear | Offshore safety-critical; DNV/Lloyd’s classed; nuclear facility |
4.3 — Applications by Industry
Metal Roofing and Cladding Through-Fastener Systems
EPDM-bonded steel fender washers (M6–M8, 22–28 mm OD) are the universal fastening element for through-fastened corrugated and trapezoidal metal roofing — billions installed globally in commercial and industrial roofing. The EPDM rubber face seals around the fastener hole through the metal roof sheet, preventing water infiltration at the most vulnerable point in a through-fastened roof system. The steel substrate distributes the pull-through load across the corrugation profile. EPDM provides 25+ years UV and weathering resistance. Zinc-flake or Galfan-coated steel substrate for maximum corrosion life matched to the 40+ year design life of the roof system. SS 316 substrate for coastal and offshore building locations.
Polycarbonate and GRP Rooflights
ISO 7093 large-series or extended fender washers (M8–M12, 25–38 mm OD, 2–3 mm thick) for bolt connections through polycarbonate dome and barrel vault rooflights and GRP translucent roofing sheets — standard plain washers pull through the brittle polycarbonate or GRP material under wind uplift load. EPDM-bonded or solid EPDM fender washers provide the weatherseal at the connection hole. The washer OD must be selected per the bearing stress calculation to keep the bearing stress below the polycarbonate or GRP allowable — typically 10–15 MPa for polycarbonate; 20–40 MPa for standard grade GRP. Oversized tightening torque is a common installation error — set a defined torque (typically 5–8 Nm for M8) to prevent polycarbonate cracking at the bolt hole.
Rubber Dock Fenders and Marine Fendering Systems
A36 HDG or SS 316 fender washers (M16–M24, 50–75 mm OD) with neoprene-faced bonded backing plate for the through-bolt connections attaching rubber cylindrical, D-section, and arch fenders to harbour walls, pier faces, and vessel berthing dolphins. The large-OD fender washer distributes the bolt bearing load across the rubber fender face without tearing through the rubber under vessel berthing impact. Neoprene is preferred over EPDM for dock fender connection washers due to its better resistance to the petroleum film contamination present at commercial harbours. SS 316 for all seawater-immersed applications; HDG for above-water and atmospheric exposure. Full EN 10204 3.1; passivation for SS variants.
Acoustic and Vibration Isolation Connections
Rubber-metal bonded anti-vibration fender washers at HVAC ductwork flange bolt connections, electrical transformer mounting bolts, compressor cover plate bolts, and suspended ceiling grid connection bolts — providing vibration isolation between the vibrating component and the building structure to reduce structure-borne noise transmission. The rubber element stiffness and natural frequency must be matched to the excitation frequency to achieve effective isolation: rubber washer natural frequency below 1/3 of the excitation frequency provides effective isolation (transmissibility < 0.1). EPDM hardness Shore A 40–50 for low natural frequency (5–10 Hz) isolation; Shore A 60–70 for higher natural frequency (10–20 Hz) isolation at higher static loads.
Offshore Grating and Decking Panel Fixings
SS 316 or Duplex 2205 fender washers (M12–M16, 37–50 mm OD) for the clip bolt connections attaching fibreglass GRP or galvanised steel grating panels to offshore platform decking frames. The large OD distributes the bolt clamp force across the GRP grating bar face — standard washers pull through the GRP bar profile under the combined wind and wave induced panel loading. Duplex 2205 for splash zone and continuously immersed connections; SS 316 for atmospheric zone decking. PTFE fender washers between the metal grating bars and the SS bolts in aluminium structural applications to prevent galvanic corrosion at the SS-Al contact zone. Full passivation per ASTM A967; EN 10204 3.1 minimum.
Solar Panel Frame and Renewable Energy Fixings
SS 316 or SS 304 fender washers (M8–M10, 25–30 mm OD, 2 mm thick) for solar PV panel frame mounting bolt connections to roofing and ground mounting structures — the aluminium solar panel frame section wall is typically 2–3 mm thick and requires a large-OD washer to prevent the bolt from pulling through the aluminium extrusion slot under wind uplift and snow loads. EPDM-faced SS 316 fender washers for rooftop PV installations where weather sealing at the panel frame connection is required. The dissimilar metal contact between SS fender washer and aluminium frame creates a low-level galvanic couple — manageable in most rooftop environments but must be avoided in coastal and industrial atmospheric locations by substituting aluminium or PTFE fender washers.
4.4 — Export Packaging Specification
- Metal fender washers bulk-packed by size (OD × hole × thickness) and coating in polybags — HDG and zinc-plated carbon steel separated from SS; size mixing in one bag avoided as OD identification in bulk is unreliable once bags are opened on site
- Rubber-faced bonded fender washers individually wrapped or face-to-face stacked with VCI poly interleave — rubber faces must not contact each other without separating film; adjacent rubber faces bond under sustained contact pressure during ocean freight
- EPDM and neoprene solid rubber fender washers packed in sealed polybags with desiccant — rubber absorbs moisture during ocean freight causing slight swelling; sealed packaging maintains dimensional stability during transport
- SS 316 fender washers in dedicated SS-labelled polybags; segregated from all carbon steel hardware and packaging; iron contamination causes rust staining on passivated SS surfaces that is aesthetically unacceptable for visible architectural and food industry applications
- PTFE and polymer fender washers individually poly-bagged by size — polymer washers cannot be bulk-packed as they deform under stack weight; visible grade marking on packaging as PTFE, nylon, and acetal are visually indistinguishable at site
- Individual lot labelling: OD × ID × thickness, material grade, coating type, and lot number on every polybag; rubber compound (EPDM or neoprene) and rubber thickness on rubber-faced washer bags
- ISPM-15 timber or cardboard export cartons for all international shipments; moisture barrier inner bags for rubber-faced and polymer washers; documentation in waterproof pocket: EN 10204 3.1 MTC, dimensional report, coating certificate, bond strength report (rubber-faced), passivation certificate (SS), PMI report, FAI report
4.5 — Complete Project Documentation Package
| # | Document | Standard / Format | Mandatory / Conditional | Notes |
|---|---|---|---|---|
| 01 | Material Test Certificate (MTC) | EN 10204 3.1 / 3.2 | Mandatory — all EPC fender washers | Coil / sheet heat-traceable; one MTC per coil lot |
| 02 | Chemical Composition Report | Mill certificate / certified lab | Mandatory | ASTM A36 / A276 SS 316 / A108 limits |
| 03 | Dimensional Inspection Report | Per ISO 7093 / ASME B18.22.1 / drawing | Mandatory | OD, hole, thickness, flatness — all dimensions |
| 04 | Coating Inspection Certificate | ISO 1461 / ISO 10683 / ASTM B633 | Mandatory — all coated washers | Thickness per face; jigging record for HDG lots |
| 05 | Salt Spray Test Certificate | ISO 9227 / ASTM B117 | Conditional — offshore; marine; roofing | Minimum hours per coating type without red rust |
| 06 | Rubber Bond Strength Report | ISO 813 peel test per production lot | Mandatory — all rubber-faced bonded washers | Min 5 N/mm (EPDM); 4 N/mm (neoprene); cohesive failure |
| 07 | Compression Set Certificate | ISO 815 — 70h at 70°C | Mandatory — rubber-faced washers | ≤ 25% compression set on rubber compound witness sample |
| 08 | PMI Report (XRF) | Per lot — SS 316 / Duplex / non-CS | Mandatory — SS and non-standard grades | SS 316 vs SS 304 for marine and offshore |
| 09 | Passivation Certificate | ASTM A967 | Mandatory — all SS fender washers | Method; Cu-sulphate or water immersion acceptance test |
| 10 | Flatness Inspection Report | Straight-edge measurement | Conditional — precision applications | ≤ 0.5 mm per 50 mm OD; press-flat before coating |
| 11 | First Article Inspection (FAI) Report | Project-specific format | Mandatory — new configurations | All parameters; released before batch production |
| 12 | ISO 9001:2015 Certificate | Third-party QMS certification | Mandatory — EPC projects | Scope covers fender washer manufacture and rubber bonding |
| 13 | Country of Origin + Packing List | Chamber of Commerce / item-level | Mandatory | HS tariff code; per-size lot quantities |
| 14 | Commercial Invoice + Bill of Lading | Per INCOTERMS 2020 | Mandatory | Freight forwarder issued |
4.6 — ISO and Quality System Compliance
ISO 9001:2015
Quality Management System covering coil and sheet stock procurement and heat traceability, progressive die stamping process qualification (OD blanking and hole punching tolerances, die wear monitoring), flatness control after stamping, HDG jigging procedure (individual washer separation to prevent face-to-face contact in zinc bath), zinc-flake coating process parameters, passivation process qualification, rubber vulcanisation process control (temperature, time, pressure records per moulding batch), bond strength test procedure qualification, and full material traceability from raw coil to dispatched fender washer. Mandatory for all EPC, roofing system, and marine project fender washer procurement qualification.
EN 1090 / AISC 360
EN 1090-2 (Execution of Steel Structures) and AISC 360 (Specification for Structural Steel Buildings) govern structural steel connections using washers. Both standards require that washers used in structural connections are from the same material grade family as the bolt and nut — SS fender washers with SS bolts and SS nuts; carbon steel fender washers with carbon steel bolts. For high-strength structural connections (A490 / ISO 898-1 Grade 10.9): ASTM F436 hardened washers are required under bolt heads and nuts — plain fender washers (unhardened, ASTM F844) are not permitted as the sole bearing element under high-strength structural bolts unless a hardened washer is also included in the assembly.
ETAG 006 / ETA Roofing
For roofing fender washers used as part of CE-marked through-fastened metal roofing systems under ETAG 006 (European Technical Approval Guidelines for Anchor Systems in Roof Cladding): the fender washer dimensions, metal grade, coating, rubber compound (Shore hardness, EPDM grade), and rubber thickness must exactly match the tested and ETA-approved assembly. Any substitution of a non-approved fender washer variant invalidates the system ETA and removes the manufacturer’s CE marking from the installed roof system — creating a liability risk for the installation contractor and the project owner. Always verify that the fender washer supplied matches the tested assembly specified in the roofing system ETA document.
FDA 21 CFR / EC 1935/2004
For PTFE, nylon, and polymer fender washers in food and pharmaceutical contact applications: FDA 21 CFR Part 177 (USA) and EC Regulation 1935/2004 (EU) govern materials in contact with food. PTFE (Part 177.1550), nylon 66 (Part 177.1500), and acetal (Part 177.2470) are all FDA-approved for food contact when manufactured from compliant resin grades. EC 1935/2004 provides equivalent EU requirements. Polymer fender washer suppliers must provide a Declaration of Compliance (DoC) per EU Regulation 10/2011 (plastic food contact materials) confirming the polymer compound and additives comply with the applicable regulations. This DoC is a mandatory documentation item for food and pharmaceutical industry fender washer supply.
Submit your bolt size, OD, thickness, material, facing type, coating, and quantity to RR Hydraulic for a complete, certified commercial offer.