Crane Safety Device Introduction

Crane safety device refers to the device that prevents the crane from being damaged in an accident. In addition to the commonly used electrical protection devices, sound signals and color lights, there are a variety of other safety devices on the crane.

 

Overload limiter

(1) The comprehensive error of the overload limiter should not be greater than 5%, and it can record the number of lifting and lifting weight.

(2) When the load reaches 90% of the rated weight, an alarm signal should be sent; When it is 100-110% of the rated lifting weight, the power supply for lifting objects should be automatically cut off through interlock control.

(3) The overload limiter shall not be adjusted or cancelled without authorization, and daily spot inspection and maintenance shall be in place and calibrated regularly.

 

Moment limiter

(1) The torque limiter is used in variable amplitude running lifting equipment such as automobile crane, crawler crane, tower crane.

(2) The comprehensive error of the torque limiter should not be greater than 10%.

(3) After the hoisting machinery is installed with a torque limiter, it should be adjusted or calibrated according to its performance and accuracy, and when the load torque reaches the rated lifting torque, the power source of lifting or amplitude can be automatically cut off, and a prohibited alarm signal is issued.

 

Upper and lower limit position limiter

(1) Lifting limit: the limit position limiter must ensure that when the spreader is lifted to the limit position, the power source of lifting is automatically cut off. For the hydraulic lifting mechanism, it is appropriate to give a prohibited alarm signal and set a deceleration limit. The heavy hammer type is more, and the electric hoist is the trigger limit switch for the rope guide.

(2) drop limit: under the working conditions that the spreader may be lower than the lower limit position, it should be ensured that the spreader can automatically cut off the falling power source when it is lowered to the limit position, so as to ensure that the winding of the wire rope on the drum is not less than the number of turns specified in the design (generally at least 3 turns).

Motion limit position protection (limit, collision avoidance device)

(1) Limit switch: also known as the operating limit position limiter, should ensure that the mechanism in its movement limit position, automatically cut off the forward power source and stop the movement, stop the limit action should be set before the deceleration limit.

(2) Collision avoidance device: When two or more cranes are running in the same span, collision avoidance devices should be installed for each vehicle, and infrared and laser ranging are used more at present. In terms of performance, laser is superior to infrared.

Buffer, track end stop

(1) The operating mechanism of the crane running on the track, the operating mechanism of the crane and the trolley should be equipped with a buffer. The buffer can be mounted on the crane or on the track end stop. The stop device at the end of the track should be firm and reliable to prevent the crane from derailing.

(2) The buffer has a good performance of absorbing the energy of the moving mechanism and reducing the impact, mainly hydraulic, polyurethane or rubber material, spring type.

Track cleaning device

When the material may accumulate on the track to become an obstacle to operation, the crane and lifting trolley traveling on the track should be installed under the frame (or end beam) and the trolley frame, and the clearance between the bottom surface of the rail sweeping plate and the top surface of the track is generally 5mm~10mm.

Anti-wind and anti-slip device

(1) There are mainly three types of wind anti-slip devices for cranes such as port machinery and outdoor gantry cranes, namely rail clamp (wheel) devices, anchoring devices and iron shoes. Tall outdoor cranes should also be installed anemometer and wind speed alarm device, when the wind is greater than the working state to calculate the wind speed set value should be able to send an alarm signal.

(2) The crane use unit should develop management standards for the use and maintenance of windproof and non-slip devices, and should focus on inspection and repair before the annual typhoon season, and supplement the deficiencies in time; Annual typhoon drills should include the operation of windproof devices and equipment.

Interlock protection

(1) The door to the bridge crane and gantry crane, the hatch door to the bridge frame from the driver’s cab and the door to the car should be equipped with an interlock protection device.

* When the door is open, the operating mechanism of the crane cannot be started.

* When the driver’s cab is located in the moving part, the passageway entering the driver’s cab shall be equipped with an interlock protection device. When the door of the passageway is open, the operating mechanism of the crane cannot be started.

(2) The rail clamp and anchoring device of the bridge door crane should be able to interlock with the operating mechanism. When the rail clamp is required to clamp the track, or the anchoring device is anchored, the operating mechanism of the crane should be automatically powered off and can be switched on when it is opened.

Other safety protection devices

(1) Deviation adjustment and display device: should ensure that the large-span gantry crane and loading bridge, when the legs at both ends are skewed due to different forward speeds, the deviation can be indicated to the driver, so that the deviation is adjusted.

(2) Level: should have a good performance to check the tilt of the leg of the crane, such as car crane.

(3) The exposed moving parts of the crane that may hurt people, such as open gears, transmission wheels, chains, belts, etc., should be installed with protective covers/fences.

(4) Electrical protection: the crane should be set up short circuit and overcurrent (overload) protection, overvoltage and voltage loss protection, zero protection, power supply fault phase protection and other electrical protection devices. The lifting mechanism of the crane adopts thyristor stator voltage regulation, eddy current braking, energy consumption braking, thyristor power supply and DC power supply, and the overspeed protection device must be set. In addition, cranes with a rated lifting weight greater than 20t for lifting molten metal should also be equipped with overspeed protection devices.