Lifting Torque limiterIt is a safety device installed on the jib crane to ensure the safe operation of the crane and prevent overload accidents. The device can effectively avoid the damage of the crane structure and the overturning of the whole machine caused by overload through the overload alarm signal or automatically stopping the crane from moving in the dangerous direction. At the same time, the crane driver can observe the lifting operation of the crane through the instrument display, so as to know the situation and provide reliable guarantee for safe production.

I Torque limiterFunction and composition of

Torque limiterIt is the specific application of electronic comprehensive measurement technology in cranes. Lifting Torque limiterThe design of the crane must first meet the requirements of the national standard gb12602-90 safety technical code for overload protection devices of cranes. At the same time, the designer can realize different functions according to the requirements of users.
Torque limiterIts main functions are:
1. Dynamic load suppression function
This device shall be able to distinguish the actual overload of the crane from the additional dynamic load caused by the sudden lifting or lowering braking during normal operation. When the suspended object is blocked or connected to the ground, it shall have the function of immediate action.
2. Automatic protection function
When the lifting mass reaches 90% of the rated lifting weight, the device will send out sound or light warning signals. When the lifting weight exceeds the rated lifting capacity, it shall be able to stop the crane from continuing to move in the unsafe direction, and send out an audible and visual alarm signal. At the same time, it shall be able to allow the crane to move in the safe direction. These actions shall be able to be performed automatically without additional operation by the crane driver.
3. Automatic insurance function
It is advocated that the product has automatic insurance function. When the product has problems or faults, the device can send out prompt alarm signals or fault codes displayed in text to facilitate timely maintenance.

II Torque limiterWorking principle of

Currently, for cranes Torque limiterThe leading product of is electrical type. Electrical products are mainly composed of sensors and secondary instruments.
For a boom crane with a fixed boom length, Torque limiterThe voltage standard value of the rated load corresponding to the actual amplitude is obtained by detecting the boom angle and calculating the boom length parameter. The load sensor generates strain after being stressed, and the strain is converted into an electrical signal, which is amplified by the amplifier and sent to the voltage comparison circuit for comparison with the voltage standard value corresponding to the rated load. When the load reaches 90% of the rated load, the early-warning comparator acts and the device sends an early-warning signal. When the load exceeds the rated load, the relay acts to cut off the power supply of the lifting circuit.

3、 Use and maintenance

Torque limiterIt is an integrated product of electrical components and mechanical components, and is an important safety device on the crane. In order to ensure its normal operation, in addition to having a basic understanding of its functions and composition, the user should operate in strict accordance with the operating instructions and strengthen daily maintenance and repair.
1. Use
(1) Before the device is put into use, the operator shall carefully read the operation manual, and the competent technical personnel shall explain its basic working principle, main performance and use method in detail.
(2) Confirm whether the type of power supply used by the device is AC220V, AC380V or DC24V to avoid burning the instrument.
(3) Self inspection shall be conducted before daily operation to confirm whether the device can work normally. In case of any abnormality, the cause shall be promptly identified and handled in a timely manner.
(4) When the lifting load of the crane is zero, the lifting capacity display part of the instrument shall show that the actual lifting capacity is zero, otherwise it shall be adjusted.
(5) In cold winter, the instrument shall be started for about 15 minutes and then used after preheating to ensure the accuracy of the instrument.
(6) If the instrument is a liquid crystal display, the temperature of the cab shall be ensured, because the liquid crystal display does not display when it is below - 20 ℃.
(7) The operator shall operate each switch or key according to the determined procedure, and operate the crane after confirmation.
(8) The operator shall specify the installation position, installation method and installation precautions of each detection element such as sensor to prevent collision damage.
(9) The connection between the sensor and the host is generally made of insulated sheathed shielded cable, which shall meet the requirements of reasonable wiring and anti-interference. The cable length shall be sufficient and shall not be too tight. Check the line regularly, and there shall be no open circuit or short circuit.
(10) The host and sensor shall be cleaned regularly to avoid the inflow of water, oil, ash and corrosive liquid. Insulation resistance shall be measured frequently.
（11） Torque limiterThe key of the main machine shall be kept by a specially assigned person. Non maintenance personnel are not allowed to disassemble the device for debugging at will to prevent failure.
2. Problems needing attention in use:
(1) The display number jump caused by dynamic load shaking is a normal phenomenon, and the weight value can be read out after the lifting weight is stable.
(2) Non professional maintenance personnel are not allowed to debug or disassemble the device at will.
(3) Although the device is a safety protection device, it is not allowed to ignore the safety operation regulations because of the installation of safety devices.