Fireproof sealing of cable trays in low-voltage electrical shafts

Fireproof board sealing of cable trays in low-voltage electrical shafts ensures fire containment, smoke prevention, and compliance with safety standards.

Key Principles

Reserved Openings: Openings in electrical shafts should be sized according to the cable tray dimensions, with an additional 100–200 mm allowance to facilitate proper sealing and installation of fireproof boards and protective steel plates. Fireproof Boards and Steel Plates: Use fireproof boards securely fixed to the shaft walls, ensuring even cuts and proper placement of fixing points. Protective steel plates, typically 4 mm thick, should extend beyond the cable tray dimensions by 200 mm and be treated with anti-rust paint and a fireproof coating.

Layered Fire Blocking: Fireproof boards should be installed in layers, aligned with water stop platforms in vertical shafts. Gaps between cables, trays, and boards must be filled with fireproof mortar to create a dense, compact barrier against fire and smoke. Sealing Gaps: All gaps around metal trunking or cable trays should be tightly sealed.

Firestop packs, mineral wool, or intumescent caulks can be used. The gap area between firestop packs and cables should not exceed 1 cm², and packing thickness should be at least 24 cm. Cover Plates: Cover plates should be square, uniform in size, and painted evenly.

They close the opening and provide additional protection against fire spread.

Material Selection

Fireproof Boards: High-density boards suitable for low-voltage cable shafts. Firestop Mortar: For filling gaps and ensuring uniform sealing. Intumescent Caulks: Expand under heat to seal penetrations and prevent smoke passage.

Protective Steel Plates: Reinforced and coated to prevent deformation and maintain fire resistance.

Installation Best Practices

Complete floor and wall finishes in the shaft before sealing. Install shaft doors and ensure proper alignment of cable trays. Place fireproof boards and steel plates securely, ensuring no visible cracks or voids.

Fill all gaps with fireproof mortar or intumescent caulk, layer by layer. Inspect the installation for uniformity, tightness, and aesthetic finish.

Compliance and Maintenance

Use preformed firestop elements or tested firestop devices to maintain safety during routine cable updates or re-penetrations. Ensure materials meet international fire safety standards such as UL 1479 or EN 1026. Regular inspections are recommended to verify that fireproofing remains intact after maintenance or cable modifications.

By following these guidelines, low-voltage cable trays in electrical shafts can be effectively sealed to prevent fire and smoke spread, maintain structural integrity, and comply with fire safety regulations.