The operating force on the roller shutter strap should be not more than 30N according to DIN EN 13659 (class 1). The max. roller shutter weight depends on the strap thickness, the guide angle and power loss on the strap guide rollers (very low for needle bearing strap guide rollers), strap roller diameter, shaft diameter, roller shutter slat thickness, slat shape (camber), weight per m² and the height to width ratio.
22 kg max. shutter weight in the case of cord drive.
Use gear coiler with zinc cord pulley for heavier weights!