Elevator Counterweight Filler: Cast Iron Concrete Types, Balance Factor 40-50%, EN 81-20 Securing and Guard Screen

The counterweight assembly consists of a structural frame (sling) and a stack of filler blocks (also called counterweight inserts, weight plates, or C/W fillers). Design basis: counterweight mass = car tare weight (empty car, car frame, car finishing) + balance factor × rated load. Balance factor: typically 0.40–0.50, meaning the counterweight is set to equal the empty car weight plus 40–50% of rated load; at half-load the car and counterweight are in equilibrium and the motor produces zero net torque; this minimises average motor power and energy consumption over a typical traffic cycle. Filler types: (1) Cast iron — standard material; dense (density ~7200 kg/m³); blocks typically 15–40 kg each; (2) Concrete — cheaper but lower density, so more volume needed; (3) Lead — used where space is very restricted (high density ~11,300 kg/m³) but increasingly discouraged for environmental reasons. EN 81-20 requirements: the filler blocks must be secured in the frame so they cannot become dislodged during normal operation or safety gear actuation; typically retained by through-bolts, wedge bars, or containment rods. After modernisation or load change, the counterweight fillers must be re-adjusted to match the new car weight and rated load. A counterweight guard (screen) in the hoistway prevents falling fillers from endangering persons in the pit.

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