Escalator Truss (Supporting Structure)The escalator supporting structure called “Truss” is the main chassis where all the machines are installed on. The truss is composed of 3 main section (Upper, middle, lower) and normally the upper and lower sections are fixed and the middle section can be altered to provide variable height.
The truss of the escalator must support the dead weight as well as structural rated load of 5000 N/m2 in compliance with EN 1993-1-1:2005 and the maximum deflection will be 1/750 of the horizontal distance between the supports. In the case of the horizontal length of truss being too long and causing more deflection than the authorized amount we have to use a middle support.
There are 2 support angles at the top and bottom of the escalator which are placed on the main construction beams of the building and are not fixed (not welded, not screw down, etc) and are only held down by their own weight.
The truss material is from different steel alloys and shapes (Tube – Angle - Channel) and combinations thereof in different sizes and a steel sheet is installed on the underside of the truss, which is called ‘Soffit’.
For the appearance of the truss, paint is used for indoor types and hot-dip galvanized for semi-outdoor and fully outdoor.
In order to assist with transportation of long escalators, the truss can be divided into 2 or more sections and during installation they are assembled with special screws in coupling sections.
The maximum deflection of the comb plate and floor plate will not be over 4 m, and comb meshing must be ensured.
Truss Enclosures Safety
1-Imperforated panels or walls must enclose all mechanically moving parts except accessible steps, pallets, belts, the part of handrail available for users and ventilation apertures.
2- Any gaps or openings close to moving parts with the risk of contact must be less than 4 mm and exterior panels must withstand 250 N at all points, at right angles in a 2,500 mm2 round or square area without breakage. Also, the fixings must be able to carry a minimum of twice the dead weight of the panels.
3- The enclosures of mechanically moving parts can be removed in restricted areas accessible to authorized personnel only, where there is no threat to the public (for example machine rooms with lock doors).
4- The cleaning of the interior of escalators and moving parts (of grease, oil, dust, paper, etc.) must be possible to prevent fires hazards.
5- Ventilation apertures must be constructed and organized according to the EN ISO 13857:2008 standard and 10 mm rigid rods cannot be passed through enclosures or touch moving parts.
6- Safety devices must be provided for any exterior panels, which can be opened.
Safety device must be provided for floor plates and also they must be opened only by keys or other tools. If the floor plate has two parts or more, a safety device must be provided for the 1st plate.
Where personnel can enter inside the machinery, the floor plate must be opened from the inside and no locks shall be considered.
Note: Only authorized personnel must access restricted internal machinery spaces.