A cable tray is a unit, or set of units, with their fittings forming a rigid structure to support cables and assist in channeling them.
The cable trays are composed of a thin metallic plate and electro-welded steel rods, the construction of which is based on the international standard IEC 61537. The standard specifies the requirements for cable tray systems, tests, and specifications.
Purpose of Cable tray
Cable trays, also called carrier trays, are mechanical support systems for cables. As trays provide a rigid structural system for cables, they are used to accommodate and safely transport all types of cables from one point to another in the project. The cables include power cables, armored cables, control and instrumentation cables, telecommunication, and fiber optic cables.
Trays are a very efficient type of channeling electrical cables, both safe and economical. Due to its ease of installation, installation costs are reduced, making maintenance and future extensions more convenient. The basic idea of a carrier tray is to arrange to wire intelligently, cleanly, and simply. Furthermore, these facilities are efficient and maintain the attractiveness of the area.
Cable trays have different characteristics that make them unique, such as their ease of fixation and installation, finishes, ventilation, resistance, design, and secrecy.
Types of Cable Trays
- Ladder type
- Perforated cable tray
- Solid background
- Basket type
- Channel type
Ladder-type or stair-case cable tray
As their name implies, these trays resemble ladders. Its structure consists of two longitudinal side rails connected by individual cross members. The carrier type allows the highest air flow between the cables, thus maintaining high ventilation levels and heat dissipation so that the cables do not exceed operating temperatures.
The steps of a ladder-type tray are perforated so that, in that way, cables with cable ties (belts) can be grouped and securely tied. These trays are usually used in the high part of buildings. In addition, they do not accumulate moisture, given their open design.
Perforated Cable Tray
A perforated cable tray consists of a bottom that has openings, and 60% of the flat area is used to support the cables placed inside the longitudinal side rails.
These trays are used for instrumentation and power cables. They are perfect for organizing large volumes of industrial power cables. Perforated cable trays can be installed on any surface and improve the cables’ useful life.
Cable trays such as these provide greater security since they isolate cables completely. With a perforated cable tray, there is no buckling or hanging. Additionally, the perforated design of the tray ensures adequate ventilation for the cables so one can maintain adequate temperatures in a closed environment space.
Solid bottom Cable Tray
A solid or smooth background tray consists of a background that has no opening, placed within the longitudinal side rails. This tray is designed to protect and support cables of all types, and the carrier tray provides maximum protection. As a result, all kinds of buckles and hangings can be avoided.
In addition, they are mostly used in pipes with small-capacity cables. These trays are designed to isolate cables completely through a hermetic closure system, which helps to prevent the buildup of heat.
Additionally, the characteristics of the solid-background carriers allow them to function as electromagnetic shields, making them ideal for protecting control and data cables from RFI interference.
It is important to note that these trays accumulate moisture. It is a problem that can be solved by performing perforations that allow continuous draining, as long as the trays are not used as a shield.
Basket-type Cable Tray
The basket-type cable trays are welded wire structures that serve to support electrical cables in an orderly way, especially systems with cables of control and data. They provide ideal support for data communication cables (coaxial and braided pairs).
These trays have the advantage of being versatile and can be used in many different situations. Due to this, it is possible to work with accessories that vary horizontally and vertically by cutting them as needed. They have other advantages, such as a light structure and more open spaces. It provides better cooling, improves electrical efficiency, and is fire-resistant. It can be used as a shield for cables.
Channel-type Cable Tray
The channel tray’s width is small, providing economical support for length drop cables. This kind of cable tray is used to carry only one or two cables to the nearby equipment from the main cable tray.
Its size is small compared to any other type of cable tray. Cable hanging can be avoided, and a safe run can be arranged with it.
Materials of Cable Tray
Cable trays are available both in metal and non-metal types
1. Metallic
Metallic trays are available in Steel, Stainless Steel, Galvanized Iron, Low-carbon steel, and Aluminum. Aluminum trays are widely used because they have the following features:
- It Resists corrosion
- Excellent strength
- Lightweight.
Steel tray provides good electric shielding, and it has low thermal expansion. The cable trays made of stainless steel have excellent corrosion resistance, and they can sustain high temperatures.
2. Non-metal
Fiberglass reinforced plastic (FRP).– It is lightweight, non-conductive & resists corrosion.
Accessories of Cable Trays
The accessories of the cable tray are shown in the picture below.
So many accessories are required for laying a cable tray. These include
- Fastener
- Clamps
- Bends
- Reducers
- T-joint
- Internal risers
- External risers
- Short straight lengths
- Coupler plates
- Tray covers
- Tray crosses
- Tray supports, and
- Endcaps
These are only a few to mention.
Advantages of Cable Trays
We have gone through cable trays and their types. Now, let us know the benefits of using them.
Installation takes less time
One of the advantages of the trays is that they take very little time to install. Compared to other solutions, such as ducts, the installation process is simpler, and they start working immediately. In addition, the fact that its installation is shorter translates into greater monetary savings for the company.
No specialization is needed to work with cable trays
One of the drawbacks of using cable ducts is that workers require additional training to feed cables safely into the duct. However, this is not a necessity with cable trays because rigorous training or expertise is not required to insert cables into the tray and install them.
Easy to maintain
Cable trays require less maintenance compared to other cable organizers. In addition, the structure of the trays facilitates the maintenance of the cables inside them. In this way, one can quickly identify damaged cables that need repair or replacement.
Less Expensive:
The cable tray costs significantly less than other wiring protection methods on the production floor.
Offers flexibility
As cable trays are usually sold in sections, their level of flexibility and adaptability of them is very high. Thus, companies can rearrange the distribution of trays and cables according to their needs. It will also be much easier to add new cables to the trays.
Disadvantage:
The moisture can build up in the solid bottom type cable tray system.
Precautions
Cable trays in the open atmosphere are necessary to withstand aggressive environmental conditions—the possibility of getting exposed to atmospheric corrosion and corrosive chemical fumes. Durable materials for cable trays need to be selected.
As part of preventive maintenance, accumulations of dust and debris on trays are to be checked to avoid fire accidents in the plant.