Instrumentation

What is Cable Tray and How it is used in Industrial applications?

Cable Tray 1

What is Cable Tray?

  • In electrical cabling , a cable tray is a metallic structure used to handle insulated electrical power distribution, control, and communication cables.
  • A cable tray is employed as a substitute for an electrical conduit, or open wiring system.
  • Normally, these cable trays are used in the industries or commercial buildings for cable management purposes.
  • Especially, these trays have advantages where changes in the wiring system are predicted and installing new or spare cables by laying them in the tray.
  • A design engineer specifies a type of cable tray that suits the project, cable specification depends upon the industrial environment or situation where it is required.
  • The selection of cable tray depends upon

1. Total number of cables used,Cable size and spacing,

2. Actual weight of all cables routed in the tray.

Describe the Purpose of Cable Tray?

Cable tray plays a vital role in industrial areas

  1. Cable trays act as a supporting system for power and communications cables.
  2. A cable tray facilitates upgrading, expanding, reconfiguring, or relocating networks.
  3. Generally, in most industrial areas the cable tray systems are open type, to allow efficient heat dissipation and easy access for replacement and repairs.
  4. Some cable tray systems are applicable for under-floor use affixed to ceilings.

Classification of Cable Trays

The cable trays are classified into different types

1. Ladder type Cable Tray

Cable Tray 2
  • The Ladder Cable tray consists of two side rails connected by rungs.
  • This type of cable tray is helpful because the ladder rung gives easy cable accessibility both from the top and bottom sides.
  • The rungs in ladder-type cable trays give suitable fixtures to tie cables for positioning of the cables in the horizontal runs in case the non-horizontal cable trays.

2. Perforated Cable Tray

Cable Tray 3
  • A perforated cable tray gives enough support to cables because this tray comprises ventilated bottom with side rails.
  • Perforated cable provides maximum strength for heavy-duty power distribution in industrial applications.
  • Pre-galvanized mild steel is used to make Perforated Cable Tray.
  • This consists of a ventilated bottom with side rails.
  • It delivers maximum support to cables compared to a ladder-type tray.

3. Solid-bottom Cable Tray

Cable Tray 4
  • Solid-bottom Cable trays are used only for routing optical fibre cables because hanging cables will influence the performance of the system.
  • Solid-bottom called non-ventilated cable trays are usually considered to minimize cable hanging.
  • This solid bottom cable tray is selected to protect from radio-frequency or electromagnetic interference.

4. Wire Mesh Cable Tray

Cable Tray 5
  • Wire mesh cable tray is also known as basket cable tray.
  • This type of tray is lined with wire mesh to fix and supports a cable of smaller diameter cable such as a data communication cable.
  • This cable tray is made up of stainless steel wires by welding wires to form the basket-shaped mesh.
  • Cable Trays are normally used for low-voltage applications, telecommunication, and fibre optic cables.

5. Channel Cable Tray

Cable Tray 6

This type of cable tray is a metallic tray used only for the installation of small-diameter (Thin) cable.

Materials used in making a cable tray

The material used for making a cable tray is decided based on the application or where it is used.

1. Metallic Cable Tray

Materials used:

a. Aluminium:

  • Aluminium is lightweight.
  • Offers an excellent strength-to-weight ratio.
  • Corrosion resistant

b. Steel:

  • Electric shielding.
  • Low thermal expansion.

c. Stainless steel

  • High corrosion resistance
  • Applicable for high-temperature range.

2. Non-Metallic Cable Tray

a. Fiberglass:

  • Nonconductive;
  • Corrosion resistance
  • Lightweight

Generally, in most industrial applications the cable trays are made up of galvanized steel, aluminium, and glass-fibre-reinforced plastic materials.

But, Galvanized trays are made by

  • Pre-galvanized steel sheet fabricated into the tray
  • Hot dip galvanized after fabrication.

In the case of the galvanized tray, usually, it must be coated with the zinc-rich compound in the broken areas to protect the metal from corrosion.

What is the Procedure for Testing a cable tray?

  • Confirmation of materials w.r.t specifications and issued for Construction drawings.
  • Visual inspection of tray dimensions such as width, rung space, height, run length & tray coating.
  • Ensure for braces and supports are adequate to handle tray weight as specified by drawings.
  • Check installed supports and braces to ensure that it is aligned vertically.
  • Check installation of connector or expansion joints is proper.
  • Check the installation of the cable tray if it does not discord or clash with equipment.
  • Check all braces and supports that are appropriate for weight handling of the tray & cables.
  • Ensure the correct and secure installation of nuts and bolts in which supports are screwed to structural steel.
  • Hold-down clamps shall be installed properly and anchored in the required locations.
  • Verify that there are no sharp edges & burr that may cut or damage the cables.
  • All metallic cable trays should be joined every 25 meters in length.
  • Coupler plates or bonding jumpers are used at every section of the tray joint for proper electrical.
  • Check Earth bonding jumpers for proper connection and joined to the main grounding grid.

What are the Factors that are to be Paid Attention to in Routing a Cable Tray?

The factors required to be paid attention to in routing a cable tray:

  • Bending Radius of BEND, ELBO, TEE, CROSS.
  • Tray Height
  • Equal or Unequal tee & cross
  • Standard bend or elbow angle 30, 45, 60, or 90 Degrees.
  • Supporting & Installation of Cable Trays.
  • Load / Weight capability per meter length.
  • Cable tray-loading & cross-section list.

Advantages of Cable Tray

  • Less expensive
  • Maintenance is easy
  • Safety

Disadvantages of Cable Tray

  • Moisture builds easily in the cable trays during winter.

What is the type of Cables a Cable Tray Supports?

Cable tray installed in industrial application supports pretty much all types of cables such as

  1. High Voltage Power supply lines.
  2. Power Distribution Cables
  3. Control cables
  4. Telecommunication cables
  5. Optical Fibre Cables

What are the three Main Types of Cable Trays?

Three main types of cable tray

  • Ladder-type cable tray
  • Ventilated trough
  • Solid bottom

What is the Importance of Cable Tray Installation?

  • Cable trays provide mechanical support for electrical cables used for power distribution, control, and communication.
  • Cable tray installation is required for running a large number of data cables overhead or under-floor.

What makes a Cable Tray Rated?

  • Generally, tray-rated cables are quality products tested to resist hardness in severe environments
  • They are safeguarded by plastic or metal Jacket.

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