2 ton to 100 ton Load Cell for Crane Limiter
Crane limiter is a kind of weighing protection device which prevents the crane from being in danger of overloading operation by detecting the lifting weight. It's also called as crane overload limiter.
The crane limiter is generally composed of two parts: Strain gauge load cell and load cell controller. The load cell is used to measure the lifting weight, while the load cell controller discriminates according to the lifting weight and outputs corresponding state control signal.
The greatest feature of crane limiter is that it effectively combines with the specific structure of lifting machinery, thus ensuring that the use of load cell and load cell controller would not destroy the safety of lifting machinery. Meanwhile, it shall also meet the functional requirements of reliable performance, convenient maintenance and high measurement accuracy.
1. Crane limiter structure
According to the specific structure of single beam or double beam crane with electric hoist, the crane limiter usually adopts the 2 ton to 100 ton tension load cell or double shear beam load cell, which are installed at the fixed end of wire rope. The load cell controllers are usually installed in the cab or above the control button station.
According to the specific structure of bridge crane or portal crane, the crane limiter usually adopts double shear beam load cells that are installed under the bearing seat of crane roller or adopts the axis load cells that are installed on the fixed pulley shaft of crane, the load cell controllers are usually installed in the cab.
Structure of bridge crane or portal crane limiter:
Bridge crane or portal crane limiter wiring diagram:
2. Crane limiter technical parameters
Scope of application: 0.5-70 ton various types of cranes
Comprehensive error: ≤ ±5%
Display error: ≤ ±3%
Motion error: ≤ ±3%
Alarm point setting:
Load cell overload capacity: 150%
Operating environment: -10~+50℃, 90% RH
Power supply: 380V-15% (+10%) 50Hz
Relay contact capacity: AC 380V 2A
Load cell protection class: IP65
Load cell controller protection class: IP42.
3. Working Principle
Load cell detects the lifting weight and the output signal is amplified by an load cell amplifier, the amplified signal is fed into the load cell controller. The load cell controller compares and discriminates the weight signal with the setting values of three reference weight signals: forecasting alarm, delay alarm and control, and immediate alarm and control, and then outputs corresponding state control signal.
The setting values of three reference weight signals are set at 90%, 105% and 130% of the rated load respectively. When the lifting load weight reaches 90% of the rated load, the load cell controller makes the buzzer ring intermittently. At the moment of lifting, the crane will produce temporary impact load due to the effect of lifting acceleration force.
To avoid instantaneous false overload caused by impact load during lifting, the load cell controller is set with the function of delay discrimination.After delaying for 1～2s, if the overload still exists, it is judged to be true overload. The load cell controller immediately outputs the signal to cut off the main lifting circuit of the crane, at the same time, the buzzer sounds continuously. Delay of overload signal is judged in a certain overload range.
If the overload is greater than 130% of the rated load, the load cell controller outputs signal to cut off the main lifting circuit of the crane no matter it's a true overload or a dynamic overload caused by impact load, meanwhile, audible and visual alarm is made, namely immediate alarm control. As the output signal of load cell controller only cuts off the main lifting circuit of the crane, it would not affect the action of descending mechanism.
The crane limiter is generally composed of two parts: Strain gauge load cell and load cell controller. The load cell is used to measure the lifting weight, while the load cell controller discriminates according to the lifting weight and outputs corresponding state control signal.
The greatest feature of crane limiter is that it effectively combines with the specific structure of lifting machinery, thus ensuring that the use of load cell and load cell controller would not destroy the safety of lifting machinery. Meanwhile, it shall also meet the functional requirements of reliable performance, convenient maintenance and high measurement accuracy.
1. Crane limiter structure
According to the specific structure of single beam or double beam crane with electric hoist, the crane limiter usually adopts the 2 ton to 100 ton tension load cell or double shear beam load cell, which are installed at the fixed end of wire rope. The load cell controllers are usually installed in the cab or above the control button station.
According to the specific structure of bridge crane or portal crane, the crane limiter usually adopts double shear beam load cells that are installed under the bearing seat of crane roller or adopts the axis load cells that are installed on the fixed pulley shaft of crane, the load cell controllers are usually installed in the cab.
Structure of bridge crane or portal crane limiter:
Bridge crane or portal crane limiter wiring diagram:
2. Crane limiter technical parameters
Scope of application: 0.5-70 ton various types of cranes
Comprehensive error: ≤ ±5%
Display error: ≤ ±3%
Motion error: ≤ ±3%
Alarm point setting:
- Pre-alarm point: 90% of the rated lifting capacity
- Delay alarm point: 105% of the rated lifting capacity
-
Immediate alarm point: 130% of rated lifting capacity
Load cell overload capacity: 150%
Operating environment: -10~+50℃, 90% RH
Power supply: 380V-15% (+10%) 50Hz
Relay contact capacity: AC 380V 2A
Load cell protection class: IP65
Load cell controller protection class: IP42.
3. Working Principle
Load cell detects the lifting weight and the output signal is amplified by an load cell amplifier, the amplified signal is fed into the load cell controller. The load cell controller compares and discriminates the weight signal with the setting values of three reference weight signals: forecasting alarm, delay alarm and control, and immediate alarm and control, and then outputs corresponding state control signal.
The setting values of three reference weight signals are set at 90%, 105% and 130% of the rated load respectively. When the lifting load weight reaches 90% of the rated load, the load cell controller makes the buzzer ring intermittently. At the moment of lifting, the crane will produce temporary impact load due to the effect of lifting acceleration force.
To avoid instantaneous false overload caused by impact load during lifting, the load cell controller is set with the function of delay discrimination.After delaying for 1～2s, if the overload still exists, it is judged to be true overload. The load cell controller immediately outputs the signal to cut off the main lifting circuit of the crane, at the same time, the buzzer sounds continuously. Delay of overload signal is judged in a certain overload range.
If the overload is greater than 130% of the rated load, the load cell controller outputs signal to cut off the main lifting circuit of the crane no matter it's a true overload or a dynamic overload caused by impact load, meanwhile, audible and visual alarm is made, namely immediate alarm control. As the output signal of load cell controller only cuts off the main lifting circuit of the crane, it would not affect the action of descending mechanism.