Design Considerations

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Loading Diagram

Cable Tray & Ladder System

Power Solution Industries offers a comprehensive range of cable tray and ladder products conforming to BS EN 61537 and NEMA VE1. To design a safe and economical system, it is necessary to consider all the loads applied to the system and establish the criteria by which it will be judged.

Loads Applied to the System

The weight of cables to be fixed on the system will provide the basic loading data. However, it is always advisable to consider that future system requirements can be expected and allow 20% for additions at a later date. The following should also be considered:
1. The capacity charts provided in this catalogue assume that loading is uniform, both along length and across width. If a point load is applied to the tray / ladder it will potentially have a significant effect and this must be quantified.
2. If components are incorporated in an exterior installation there may be other loading factors to consider, such as wind, ice and snow.

Safe Loading and Deflections

Cable tray & ladder acts as a structural load carrying beam when installed horizontally. The loads imposed and the type and location of supports will create a pattern of bending moment in the structure. Stress will be induced and deflections (vertical displacements) will be observed. A properly specified system will ensure that the stress does not exceed to that which is safe for the materials used in the components.

A suitable installation will require choice of appropriate style of tray / ladder and the location of supports. Increasing the span (horizontal distance between supports) will always reduce safe load carrying capacity and increase deflection.

Location of Supports and Connections

Normally cable tray / ladder is connected together forming a continuous beam over several supports. A typical bending moment diagram shown on the previous page shows the following:

1. Bending moment is much larger in the end spans of the continuous beam than the intermediate spans; which will reduce the load carrying capacity in the end spans. If an installation requires full load carrying capacity along the whole length, than full capacity of the intermediate spans can be used if the end spans are reduced to 0.75L (length of intermediate spans).

2. Bending moment is zero at approximately 0.25L either side of the intermediate supports. These are therefore ideal places to locate connections between component lengths of cable tray/ladder. The installer should avoid placing connections in mid-span positions and at supports. These are positions of maximum bending moment.

3. The diagram shows a typical multi-span beam loading condition. If a loading condition occurs where there is only a single span loading condition it can be taken that the permissible load is reduced to 0.5 that shown for intermediate span in multi-span beams.

4. Only straight length beams are discussed above. When accessories (bends, tees, risers etc.) are involved in an installation they will require extra local support. It is always recommended to use fish plates in conjunction with connectors, particularly when cable trays of greater than 200mm are used. Where earth continuity is an important consideration in a cable tray or ladder system, bonding jumper leads should be used. Cable ladders runs exposed to wide ambient temperature & the variation should incorporate expansion connectors.

Cable Trunking System

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Standards Finishes:
PG Pre-galvanized to BS EN 10142 & 10143
PC Power Coating to suit clients requirements

  • PSI - Cable Trunkings are manufactured compling to BS 4678 Part1
  • PSI - Cable Trunkings are manufacured to a standard length of 3 mts but can be produced to any desired length also on request.
  • PSI Cable Trunkings are manufacutred with jet lock & screw fixing covers. Jet lock arrangement requires only a quarter rotation of the turn buckle for fixings.
  • PSI Cable Trunking straight lengths are joined by connectors. Connectors are supplied in pairs with trunkings along with neccessary fastners For details refer page.
  • PSI-Cable Trunking Accessories are produced out of single piece and require no welding. Accessories are produced with integral connectors & require no seperate connectors for joining.
  • PSI-Cable Trunking Accessories are manufactured to a standard radius of 300mm, but can be produced to the radius of 600mm & 900mm also, on request.
  • PSI-Cable Trunkings can be produced with different thickness also for custom designed requirements.

Trunking Capacity Guide

The following guide will help you to select the correct size of trunking for the required number and size of cables in your installation. It has been prepared from Appendix 12 of the I.E.E wiring regulations for electrical installations. When cables are pulled into trunking they experience a drag from other cables and from the trunking itself. Using this guide to select the size of trunking for your cabling will ensure that an acceptable pulling force is required to install the cables and that minimum damage to the installations will occur. This is only a guide and is designed for use with single core PVC insulated.

To use this guide:

  • Calculate Capacity unit by multiplying the Number of cables by the factor from Table A.
  • Use capacity unit to choose nearest size of trunking from table B.
  • Remember that cables can cross over each other and that you may need space for future wiring. Consequently, select the next size up.

Metal Framing System

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The standard material finish for strut channel and brackets is HDG Hot Dip Galvanised. The mild steel used has a yield of at least 250 N/mm2

Power Solution Industries offers a comprehensive metal framing system that conforms to BS 6946:1988 (Metal channel cable support systems for electrical installations).

The Power Solution Industries system incorporates the following features Flexibility of elements of the system can be combined to create an unlimited range of structural designs.

  • Rigidity of easily assembled rigid structures can be created without the need for drilling and welding.
  • Adjustability of position of components can be easily adjusted & structures can be demounted and components reused.
  • Competitiveness & high strength to weight components and ease of assembly make this a cost effective solution to support structural requirements.
  • It has many applications for structural support of mechanical as well as electrical services in a wide range of industries and construction projects.