Although they are essential part of every metro station, little is known about how to mount or to maintenance them, even though the process requires great care and organizing works from the experts.
During their replacement, the old escalators are demolished. Most of their more easily movable parts and their components are removed, finally almost only the steel frame remains. These works are carried out with special lifting equipment. After the renovation of their concrete shafts, the new escalators may be installed.
The new devices consist several separable units, typically the lower, upper and middle elements. The weight of one such item can be up to 3-4 tonnes. The units transported to the scene are lowered to the underpass level by a temporary ramp, and moved by roller wagons to the place where they are installed, by means of hand-operated winches mounted on the lifting points in the superstructure (also used for dismantling the old stairs).
When assembling the new equipments, they measure the exact position of their track. After all the components and coverages hace been assembled and set up, fine-tuning of each component is performed during the test run. After the final expert examination the officials may authorize operation of new escalators.