Load moment indicators

The Valla load limit indicators have been designed to provide cranes with appropriate safety protection. The load indicator automatically compares the weight to be lifted with the maximum load bearing capacity of the crane.

The principle information that the Valla load indicators provide operators with so that they can work in the maximum of safety are:

• lifting load;
• maximum load;
• upsetting percentage ;
• lighting lamps (green, yellow, red);
• operating radius;
• boom angle;
• boom unwinding;
• other particular conditions.

The system determines the lifting load using the appropriate sensors (pressure transducers) along with the angle measurements and the boom unwinding. It then automatically calculates the operating radius

The load to be lifted is continuously compared to the maximum load that the crane can lift, taken from the lifting load table. From this there are three possible conditions:

Safety

•  green light is on;
•  no acoustic signal present.

This means the lifted load is less than 90% of the maximum allowable load.

Pre-alarm

•  yellow light is on;
•  buzzer gives out an intermittent sound.

The situation is a pre-alarm and is present when the lifted load is more than 90% and less than 100 % of the maximum allowable load.

Alarm

•  red light on;
•  buzzer gives out an uninterrupted sound.

Blocking occurs when the lifted load is more than the allowable load and the stop manoeuvre goes into action. At this moment the only operations permitted are those that consent restoration of crane safety.