ISO 15236-4:2004

Overview

ISO 15236-4:2004 specifies the design, dimensions, requirements and marking of vulcanized joints for steel cord conveyor belts. It is part of the ISO 15236 series for steel cord conveyor belts and focuses on splice types, material and manufacturing guidance to ensure reliable force transfer and long service life of belt joints.

Key topics and technical requirements

• Scope: Applies to vulcanized splices (joints) where cords from two belt lengths are merged and vulcanized through the surrounding rubber.
• Types of joints:
  • Stepped joints - forces transferred primarily through the surrounding rubber; available as 1‑ to 4‑step (or more) designs, including plain and interlaced variants.
  • Finger joints - require transverse reinforcement and are normally limited to small cord diameters (maximum ~3.3 mm); tongues (“fingers”) from each end interlock and are vulcanized.
• Cord transition and spacing:
  • Transition lengths for interlaced stepped joints depend on cord diameter; preferred values include 100 mm (d ≥ 6.0 mm), 150 mm (d > 6.0–≤8.5 mm), 200 mm (d > 8.5–≤10.0 mm), and 250 mm (d > 10.0–≤11.5 mm). Minimum transition length is not less than 16× cord diameter.
  • Minimum cord spacing in plain stepped joints is specified as the cord diameter plus the required rubber gap.
• Rubber gap and butt clearance:
  • The standard requires a minimum rubber gap between adjacent cords from different belt ends (formula based on cord diameter is provided in the standard).
  • Butt end clearance of cord ends should be approximately 4× cord diameter but not less than 3× cord diameter.
• Reinforcements:
  • Transverse reinforcements reduce peak stresses; if used they must end at least 50 mm from the cover transition.
  • Finger joints require transverse reinforcements for acceptable strength.
• Manufacturing parameters:
  • Heating platens must extend at least 150 mm beyond the joint longitudinally and cover side irons transversely.
  • Curing pressure should be applied evenly, with a minimum of 1 MPa; mechanical presses must distribute pressure uniformly.
  • Guidance on preparation: bevel cover transitions, leave adhesion rubber on cords, and fill gaps with high‑quality bonding rubber.
• Marking:
  • Permanent, easy‑to‑read markings: characters at least 20 mm high and 3 mm line width.
  • Example format includes date, manufacturer, joint number and vulcanizer ID (e.g., “6/94 NN 15 21”).

Applications and who uses it

• Primary users: belt manufacturers, onsite vulcanizing service providers, conveyor maintenance engineers, quality and safety managers.
• Applications: design and fabrication of in‑field vulcanized splices for mining, bulk materials handling, quarrying, ports and industrial conveyor systems where steel‑cord belting is used.
• Benefits: provides repeatable joint design and manufacturing criteria to optimize dynamic performance, fatigue life and workplace safety.

Related standards

• ISO 15236-1 - Design, dimensions and mechanical requirements for conveyor belts for general use
• ISO 15236-2 - Preferred belt types
• ISO 15236-3 - Special safety requirements (underground applications)
• ISO 15236-5 - Marking

Keywords: ISO 15236-4, vulcanized belt joints, steel cord conveyor belts, stepped joints, finger joints, conveyor belt splicing, vulcanizing, joint marking, belt maintenance.