Types of Cable trays, and it’s selection.

A cable tray is a rigid support structural system used to securely fasten, or support cables or trays.

Cable Tray is used to supporting a large number of cables or conduit tubing between the two points. Tray material shall be selected according to environmental conditions and installation requirements.

Cable trays offer higher safety, reliability, enhanced space utilization, lower cost as compared to electrical conduits. 

Purpose:

  • Provides protection and easy access to the cables.
  • For fire prevention.

Various types of cable trays are commercially available in the market, one can select based on their environment, organizational needs. Each cable tray system has some merits and demerits when compared to others.

Cable separation and segregation:

Control cables (low voltage) are to be carried out in separate trays to avoid electromagnetic interference from power cables (high voltage).

Cable tray types:

Solid bottom tray

Channel tray

Ladder tray

Wire mesh tray

Perforated tray

Solid bottom tray:

The Solid bottom tray provides maximum protection to the cables. Solid bottom cable trays are chosen for optic fiber installations where the dropping off the cable may affect system performance. Electromagnetic interference/radio frequency interference can be overcome by selecting a solid bottom cable tray.

As can be seen in the above figure, the general size description of any cable tray can be in Length * Height * Width * Thickness.

Merits:

Good strength.

Demerits:

Moisture can build up in the cable trays.

Cable heat dissipation needs to be taken into account.

Channel Tray:

Channel cable tray provides cost-effective support for cable drops and branch cable runs from the backbone cable tray system. Channel cable tray used for installations of a limited number of tray cables when the conduit is unacceptable.  

Ladder Tray:

Ladder tray ( looks like a ladder) is typically used in feeder applications for longer runs of multiple cables for higher current carrying capacity and weight. Ladder tray can be cut, shaped, and fitted easily in either horizontal or vertical planes.

Merits:

  • Provides maximum airflow and heat dissipation.
  • The rungs in the tray helpful in tying.

Demerits:

Provides less support than any other cable tray system.

Wire mesh type tray:

Cable trays are used in all types of industries, including fiber optic installations in data centers and offices of electronic data processing centers. Mesh cable tray also referred to as “cable basket” is less expensive than other methods of cable laying.

Merits:

  • Fast and easy to install.
  • Flexible cable management options.
  • Protection from rodents.
  • Lightweight but rigid.
  • Low cost. 

Perforated cable tray:

A perforated cable tray has opened at the bottom of the tray. Perforated cable tray supports higher cable fill because of better airflow support around the cables. Perforations support cable tying and it is a great advantage.

Merits:

  1. Air circulation around the cables.
  2. Prevent liquid or droplet trapped.

Demerits:

Often cable trays are hard to reach, go unattended for debris and combustibles buildup within the tray.

Tray materials:

Common cable trays are available with materials made of 316 SS, GRP, Galvanized Iron, Aluminum, Glass-fiber reinforced plastic.

Cable cover:

The tray shall be protected with a tray cover for installation where the chances of fallen objects such as a liquid spill, debris, etc, on the tray may exist.

  • Ventilated tray cover
  • Solid top tray cover

Cable Tray accessories:

Straight Tray- Standard Length is 3 meters.

Bend – Used for Directional change turns the route right or left.

Riser – It is used for directional change in the vertical direction – turns up or down.

Tee- It is Used to take a new branch from the existing route.

Reducer- Used to modify the width of cable tray systems based on cable runs.

Cross – Which allows the intersection of two tray routes.

Splice Plates- Used to connect two individual fittings.

Adjustable splice plates- are similar to hinges indoors, we can adjust the angle as required while connecting the two fittings.

Nuts & Bolts- Used to connect two fittings.

Factors that are to be paid attention in cable tray routings:

Bending Radius of BEND, ELBO, TEE, CROSS.

Tray Height

Equal or Unequal tee & cross

Angle for bend or elbow (30,45,60,90 – standard angle)

Supporting & Installation of Cable Trays.

Load / Weight capability per meter length.

Cable tray-loading & cross-section list.

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