Returning to Large/Underground Network Lifts & Uncontrolled Movement of Ascending Lifts

EN 81-1 : 1998 stipulates that traction Lifts/Elevators must be equipped with a DEVICE that stops the Ascending Lift Car or reduces its speed to that for which the Counterweight Buffers are designed, if the speed exceeds 115% of Rated Travel Speed. This device should act directly on the Lift Car, on the Counterweight, on the Rope System or on the TRACTION SHEAVE.

BRAKING SYSTEMS as per the CB 160 with two Safety Gear Sets preventing the Lift/Elevator from uncontrolled movements in both directions, manufactured by Wittur Aufzutgeile GmbH such as the KB160 with two Safety Gears, the upper one being actuated when the Lift Car exceeds the pre-determined value when travelling upwards while the bottom one functions as a conventional Safety Gear.

Another Bi-Directional Safety Gear Designated BFD2D-1 Manufactured by C. Hausahn GmbH and supplied in two different housings they are activated by an overspeed governor tripping in both directions of the "governor" rotation.

In Tandem Arrangements the force needed for stopping the Ascending Lift Car is lower than that required for the Down Direction.

Furthermore the Safety Gears should be designed and be capable of being operated by a single overspeed governor. The most convenient governor is a Bi-Directional Friction Governor operating in both directions, For sufficient governor force in the Up Direction, the governor tension weight may need increasing and also fitted with a lockdown device to prevent the loss of TENSION.

John Irwin C. Eng. M. I. Mech. E. of 22 Princess Court, Queensway, London W2 4RB.