The allowable deviation in thickness for fireproof cable trays is generally governed by IEC 61537 and related standards, with typical tolerances ranging from ±5% of the nominal material thickness, depending on the manufacturer and coating type.

Standards and Guidelines

Fireproof cable trays must comply with IEC 61537, which specifies construction, mechanical strength, and coating requirements for metallic cable trays, including galvanized steel, stainless steel, and fire-resistant coated trays . The standard ensures that trays maintain structural integrity under load and during fire exposure. Coating thickness tests are part of the compliance verification to ensure durability and fire resistance .

Typical Tolerances

• Metallic trays: For galvanized or stainless steel trays, the thickness deviation is typically ±5% of the nominal thickness, depending on the galvanization or coating process used .
• Fireproof coatings: Flame-retardant paints or fire-resistant coatings applied to trays should meet manufacturer specifications, with thickness tolerances usually within ±10% to ensure consistent fire performance .
• Installation tolerances: While not directly related to material thickness, fireproof cable trays must also be installed with horizontal deviation ≤2 mm per meter and vertical deviation ≤3 mm per meter to maintain mechanical stability and fire integrity .

Fireproofing Considerations

Fireproof cable trays often include internal fire barriers to isolate different fire zones and slow flame propagation . The tray material and coating thickness must be sufficient to maintain circuit integrity during fire exposure, typically tested for durations such as 90 minutes under DIN 4102-12 or equivalent standards . Deviations beyond specified tolerances can compromise fire resistance and mechanical performance.

Practical Recommendations

• Always refer to the manufacturer's datasheet for exact thickness tolerances and fireproofing specifications.
• Ensure that coating thickness is measured after fabrication and before installation.
• Maintain proper support spacing and alignment to prevent deformation, which can affect both mechanical and fireproof performance . By adhering to these standards and tolerances, fireproof cable trays can reliably support cables while maintaining safety and compliance in fire-prone environments.