ISO 8535-1:2016

Overview - ISO 8535-1:2016 (Diesel engines: steel tubes for high‑pressure fuel injection pipes)

ISO 8535-1:2016 specifies dimensions, material and processing requirements, surface quality criteria and test methods for seamless cold-drawn single‑wall steel tubes used in high‑pressure fuel injection pipes for diesel (compression‑ignition) engines (class 2) and for fuel‑injection pump testing (class 1). The standard covers diameter/length tolerances, bore surface grades, minimum mechanical properties, corrosion protection, straightness, cleanliness and required tests and certificates.

Key topics and technical requirements

• Scope / classes: Applies to diesel engines - class 1 (pump testing) and class 2 (engine service).
• Dimensions & tolerances:
  • Recommended inside/outside diameters are given (Table 1).
  • Inside diameter tolerances: d ≤ 4 mm → ±0.05 mm (class 2) or ±0.025 mm (class 1); d > 4 mm → ±0.10 mm.
  • Outside diameter tolerances: D < 8 mm → ±0.06 mm; D ≥ 8 mm → ±0.10 mm.
  • Concentricity of OD to ID is limited proportionally to wall thickness.
• Material & processing:
  • Made from unalloyed or equivalent quality steel with homogeneous structure.
  • Final cold‑drawing reductions followed by heat treatment to achieve specified mechanical properties.
• Surface quality & bore grades:
  • Outside and inside surfaces must be free of scale, laminations, deep pits or injurious defects.
  • Bore grades S, R, Q, P, O define permitted imperfections and required magnification for inspection (S = ×50, up to five imperfections 0.08–0.13 mm; O = ×500, all imperfections ≤0.01 mm).
• Surface finish & corrosion protection:
  • Outside surface may be plated (e.g., zinc + chromating) or chemically treated; inside surface must remain uncoated. Note: some finishes are not recommended for light alcohol fuels (e.g., methanol).
• Mechanical properties:
  • Codes 1–6 specify minimum tensile strength, proof strength, elongation and Vickers hardness (e.g., Code 1 ≈ 310 N/mm2 tensile, 205 N/mm2 proof, 30% elongation, 115 HV; higher codes increase strength/hardness).
• Testing:
  • Dimensional checks, tensile/hardness tests per ISO 6892‑1 and ISO 6507‑1, bending test (180° around a rod = OD), cold upsetting for OD ≤ 15 mm, inside pressure tests, surface quality inspections and lot acceptance rules. Cleanliness per ISO 12345.

Applications and users

• Intended for tube manufacturers, fuel‑injection pipe assemblers, engine OEMs, suppliers of high‑pressure fuel systems, testing laboratories, quality and procurement engineers.
• Typical uses: high‑pressure fuel lines in diesel engines, fuel injection pump test rigs, replacement tubing for service/repair. Compliance ensures safety, dimensional interchangeability, corrosion resistance and reliable performance under high pressure.

Related standards

• ISO 6892‑1 (tensile testing), ISO 6507‑1 (Vickers hardness), ISO 12345 (cleanliness), ISO 4093 (tolerance reference). These referenced standards define specific test methods and acceptance criteria used by ISO 8535‑1:2016.