Tower crane must be equipped with weight limiter, moment limiter, height limiter, travel limiter, amplitude limiter, etc.
(1) weight overload limiter: also known as overload limiter, is a kind of insurance device that can make the crane not overload operation. When the lifting weight exceeds the rated weight, it can automatically cut off the power of the lifting mechanism to stop or give an alarm. Lifting limiter has two kinds of mechanical and electronic.
(2)Load Moment limiter: for the luffing crane, a certain amplitude is only allowed to lift a certain lifting weight, if overweight, the crane will have the danger of tipping over. Moment limiter is a kind of protection device developed according to this characteristic. In a certain range, if the lifting exceeds its corresponding weight, the circuit is cut off, so that the lifting can not be carried out, to ensure the stability of the crane. There are three kinds of moment limiter: mechanical, electronic and compound.
(3) Height limiter: also known as hook height limiter. Generally installed in the head of the lifting arm, when the hook slides up to the limit position, it will hold the lever. Voltage lower limit switch, cut off the circuit to stop, and then close, the hook can only fall.
(4) Travel limiter: the safety device to prevent the crane from crashing or limiting the driving within a certain range. It is generally installed on the inside of the active trolley, mainly to install a trip switch that can toggle the lever. In addition, a fixed limit position baffle is installed at the end of the track (in the limited position of operation). When the tower crane runs to this position, the limit baffle touches the lever of the travel switch to cut off the power supply to control walking, and then the tower crane can only run in the opposite direction.
(5) Range limiter: also known as the amplitude limit or range indicator, the general boom crane on the lifting arm are hung with an range indicator. It consists of a fixed circular indicator plate, in the center of the plate is installed a lead moving pointer. When the amplitude is variable, the pointer indicates the rated lifting weight at various amplitudes. When the arm runs to the upper and lower limit positions, the lower limit switch is respectively pressed, the main control circuit is cut off, and the amplitude motor is stopped to achieve the function of limit.
