Cable Trays: Selecting Bends, Couplers and Support Systems

Short Answer

Corner sections and connectors must be selected strictly according to three parameters of the straight trunking: the base width, the side height, and the series (type) of a specific manufacturer's system. A "200×50" corner from one brand is not guaranteed to fit a "200×50" straight section from another: perforation patterns for fixings, interlocking mechanisms, and side profiles will differ. Therefore, the first rule is to kit out the installation with fittings from the same series as the straight sections, ideally consolidating the entire specification under a single manufacturer.

The second rule is to calculate fittings and fixings simultaneously with the straight sections. In a real-world installation, every turn requires a corner (horizontal or vertical, internal or external—these are three distinct products), and every joint between straight sections requires a splice plate with fasteners. Furthermore, the entire metallic containment system must form a continuous electrical circuit and be connected to the protective conductor in accordance with HD 60364 requirements.

Trunking types and their impact on procurement

Cable containment systems are divided into four main types, each with its own specific range of fittings.

Trunking Type	Construction	Applications	Procurement Notes
Solid sheet metal (non-perforated)	A continuous enclosure made of sheet steel, often with a cover	Routes requiring protection from dust and debris, outdoor sections, or extra-low voltage (ELV) runs near power lines	Covers must be ordered separately for straight sections and separately for corners, tees, and crosses
Perforated sheet metal	The same enclosure as above, but with perforations in the base and sides	The primary type for industrial and office installations	Perforation facilitates cable fastening with ties; corners and connectors are the same as those for the solid version of the same series
Ladder type	Two longitudinal side rails with transverse rungs	Heavy cable loads, long spans, and vertical shafts	Requires a dedicated range of fittings (specifically designated "for ladder type"); includes base inserts and bend radius limiters
Wire mesh	Welded steel wire mesh	Lightweight loads, ELV, server rooms, or environments requiring high cable ventilation	Corners are often formed on-site by cutting and bending the mesh; fittings primarily consist of connectors and fixings

In product catalogues, these types are categorised separately: sheet metal, ladder, and wire mesh trunking.

Corner sections: types and sizing

Three types of corners — for three types of turns

A turn in the horizontal plane and a turn in the vertical plane are different products:

• Horizontal bend — a turn in the plane of the base (e.g., bypassing a column or turning a corridor);
• Vertical internal bend — the route turns upwards "inward" (e.g., transitioning from a horizontal section to a vertical rise along a wall);
• Vertical external bend — the route turns downwards, turning "outward".

Dimensions: width, height, thickness, and coating

The range of dimensions for bend sections is as follows:

• Tray width: standard range of 50, 80, 100, 150, 200, 300, 400, 500, 600 mm; some series extend up to 700–1000 mm;
• Side height: common sizes are 50, 80, and 100 mm, as well as 35, 150, and 200 mm;
• Metal thickness: from 0.6 to 2.0–2.5 mm (typical increments: 0.7 / 0.8 / 1.2 / 1.5 / 2.0 mm);
• Coating: continuous hot-dip galvanisation (standard for indoor use), pre-galvanised (electro-galvanised), hot-dip galvanisation or zinc-flake coating (for outdoor or corrosive environments), powder coating, and stainless steel for chemical or food industry applications.

The bend must match the straight section in all four parameters. This is particularly critical regarding the coating: using a bend with pre-galvanised coating in a system of hot-dip galvanised trays outdoors will result in corrosion starting specifically at the bend.

Comparison: one dimension across three manufacturers

For reference, here are 90° horizontal bends for a 200×50 mm tray from three major brands in the catalogue:

The price difference between items of the same dimension is primarily due to metal thickness, whether mounting hardware is included (some premium series come complete with fastening elements), and the type of coating. Budget lines are often made from thinner sheet metal—sufficient for light cable loads, whereas heavier installations require thicknesses of 1.2–2.0 mm.

Connectors: joining sections

The connector category contains several different types of products, each with a specific purpose:

• Splice plate — the basic element for joining two straight sections. It is selected based on the side rail height (35, 50, 80, 100 mm, etc.), installed in pairs on both rails, and secured with screws and nuts from the same kit or separately;
• Hinge plate (vertical hinge) — connects sections at an angle in the vertical plane. This allows for the assembly of rises or drops with non-standard angles without requiring a pre-fabricated angle section;
• Adjustable splice plate — similar to the hinge plate, used for variable angles, including in the horizontal plane;
• Base cover / joint cover — covers the joint from below to prevent cables from resting on the sharp edge;
• Connectors for wire mesh and ladder trays — separate product lines; the manufacturer explicitly specifies compatibility, e.g., "suitable for wire mesh tray" or "suitable for ladder tray".

The key selection parameter is the side rail height of the tray: a plate for h=50 mm will not fit a tray with an 80 mm rail. The tray width is not critical for standard splice plates (as they are mounted on the rail), but it is essential for base covers.

Example of a typical solution for a non-standard vertical turn — a hinge plate for a 50 mm rail:

Earthing the installation

A metal cable tray is an exposed conductive part, and according to HD 60364 requirements, the installation must be connected to a protective conductor. Requirements for protective conductors and earthing arrangements in buildings are also governed by the HD 60364 series (specifically regarding the selection of protective conductors, see HD 60364-5-54). In practice, this means:

• Circuit continuity along the entire length. Bolted connections between sections using standard joining plates typically provide metal-to-metal contact when tightened; however, design specifications often require additional bonding jumpers at joints—especially on coated trays, where the coating acts as an insulator. The final decision rests with the designer; jumpers specified in the project must not be omitted without authorisation.
• Connection to PE — at the start and end of the run (and as specified by the design), using a conductor of the appropriate cross-section connected to a point where the coating has been removed or to a dedicated grounding terminal.
• Covers. For routes where the cover must also maintain electrical continuity, covers with integrated grounding are available—manufacturers offer specific ranges of grounded covers for base widths from 50 mm to 200 mm and lengths of 2000/3000 mm.
• Using the tray as a PE conductor for powered equipment is only permitted if explicitly specified in the design and if the requirements for continuity and conductivity are met according to HD 60364; by default, a cable tray is considered a structural component rather than a protective conductor.

Load and support spacing

The load-bearing capacity of a tray system is determined by the metal thickness, side rail height, tray width, and support spacing. The testing methodology for cable management systems is defined by relevant standards (such as EN/IEC 61537). Practical guidelines for specification:

• Only use the permissible load values provided in the manufacturer's tables for the specific series and the specific support spacing—there are no "universal" figures;
• Corner and T-junction sections are the most heavily loaded points of the route: cable flows converge from two directions at these points, therefore supports (wall brackets, floor stands, or ceiling profiles) should be placed at every shaped element, not just on straight sections;
• The joint between two sections should not be left suspended in the middle of a span—it should be positioned near a support;
• For heavy cable loads in ladder trays, reinforced base plates and bottom inserts are available as separate product categories.

Typical tray specification errors

1. Using fittings from a different manufacturer or series. A "200×50" dimension in a product name does not guarantee matching perforation patterns or locking mechanisms. To ensure continuity, use a single manufacturer and a single product series for the entire installation route.
2. Forgetting covers for fittings. Covers for corners, tees, crosses, and reducers are separate items. If you only order "tray + cover" for straight sections, the corners and tees will remain exposed.
3. Failure to account for fasteners. Some series include mounting hardware (bolts, nuts, etc.), while others do not. Always verify the product specifications, otherwise you may run out of screws and nuts on-site.
4. Mixing finishes. Electro-galvanised coatings used in budget fittings may corrode much faster than hot-dip galvanised finishes when used outdoors or in aggressive environments. A single low-quality corner can compromise the service life of the entire installation.
5. Changing width without a reducer. When the tray width changes (for example, reducing from 400 mm to 200 mm after a branch), you must use a standard reducer rather than attempting a makeshift connection.
6. Lack of an earthing solution. It is more efficient to include earthing links, PE connection points, and covers with integrated earthing in the initial order rather than purchasing them later to satisfy technical supervision requirements.

Catalogue availability

When designing a cable tray route from scratch, the workflow should be as follows: select the tray type and series based on the expected load and environmental conditions; calculate all bends (separately for horizontal and vertical), joints, branches, and width transitions according to the layout; add connectors based on the number of joints; include covers for both straight and shaped sections; specify supports using the manufacturer's recommended spacing; and include earthing components. Following this systematic approach ensures the route can be assembled without the need for additional last-minute orders or improvised inserts.