FRP cable trays are used to support and route electrical cables in corrosive industrial environments where metal trays would deteriorate quickly. Installation is similar to metal tray in principle—support the load, align the sections, secure the fittings—but FRP has its own material behaviors that affect how you space supports, make connections, and handle grounding. Getting these details right at installation prevents sagging, joint loosening, and electrical safety problems later.

What Makes Up an FRP Cable Tray System

A typical FRP cable tray system includes straight ladder or perforated sections, horizontal and vertical bends, tees, crosses, splice plates, and support brackets. The tray itself is made of glass fiber reinforcement embedded in a thermosetting resin matrix, usually polyester or vinyl ester. Unlike steel, FRP does not yield under overload—it deflects gradually and then fractures. This means support spacing and load verification are critical, not optional.

Support Spacing: Configuration Dependent, Not a Fixed Number

The correct distance between supports depends on several factors: tray width, side rail height, fiber architecture, resin type, cable load, and the allowable deflection limit for the project. There is no single “standard” spacing that applies to every FRP tray. For example, a narrow ladder tray carrying a few instrument cables can span farther than a wide tray loaded with power cables.

Industry references such as NEMA VE 1 provide general guidance for FRP cable tray design and performance, but the specific load-deflection data always comes from the tray manufacturer’s tested configurations. Engineers should use that data to select support spacing that keeps deflection within project limits—commonly L/100 or L/200 of the span, depending on the specification.

For most industrial installations, support spacing for FRP tray falls within a practical range, but you should not rely on a rule of thumb. If the manufacturer’s data is not available at the design stage, request it or use conservative spacing until confirmed.

Fittings and Connections

FRP tray sections are joined with splice plates and fasteners, typically made of the same or compatible FRP material or 316 stainless steel. Avoid using plain carbon steel hardware, as it will corrode and stain the surrounding area. When tightening bolts, follow the torque recommendations for FRP—over-tightening can crush or crack the laminate. A common practice is to use flat washers on both sides to distribute the load.

Bends, tees, and crosses are normally factory-made to match the straight sections. Field modifications are possible, but any cut edges must be re-sealed with a compatible resin topcoat to prevent moisture wicking. The same applies to drilled holes for cable drop-outs or drain points.

Grounding and Electrical Continuity

FRP itself is non-conductive, which means the tray does not provide a natural grounding path like steel or aluminum. If the electrical design requires the tray system to be bonded or grounded, you must install an external bonding conductor—typically a copper or tinned-copper conductor attached to the tray at specified intervals. Some FRP tray systems include embedded conductive elements, but this must be verified with the manufacturer and shown on the project drawings. Without such provisions, do not assume the tray is part of the grounding system.

The actual grounding requirements come from the electrical code and the project specification, not from the tray material alone. Always coordinate with the electrical engineer on the project before finalizing installation details.

Field Cutting and Edge Sealing

Cutting FRP tray on site is common for final length adjustments. Use a diamond or carbide-grit blade and work slowly to avoid delamination. After cutting, the exposed fibers must be sealed with a compatible resin topcoat. Unsealed edges can absorb moisture and chemicals, leading to progressive degradation. This step is especially important in outdoor or wash-down areas.

Thermal Expansion and Contraction

FRP expands and contracts more than steel with temperature changes. For long straight runs, allow for expansion at joints or use expansion splice kits if specified by the manufacturer. Do not rigidly anchor every tray section; instead, use slotted holes at intermediate supports to allow longitudinal movement while maintaining vertical support.

Load Verification After Installation

After the tray is installed and cables are placed, visually check for excessive sag between supports. Deflection should be within the project limit. Also check that all splice plates are tight, cut edges are sealed, and the bonding conductor (if required) is continuous and properly terminated.

FRP cable tray installation is straightforward when the support spacing is based on real load data and the field modifications are sealed correctly. The material behaves differently from metal, but with attention to these details, it provides decades of service in environments where steel would fail in a few years.