Crush Guard - User - Operating The System

The Crush Guard® is designed to cut off the EWP movement when an object impacts the operator from above or behind - and they fall over the controls.

The Crush Guard consists of a mechanical frame that runs a wire rope over the operator controls. In the bottom left corner is the magnetic release to apply tension to the wire rope. In the bottom right corner is the override and reset switch to return the platform to normal operation once the alarm is triggered. This is connected to the control module which is mounted beneath the operator controls.

The control module is powered from the EWP operator controls. For the first 2 seconds of operation, the Crush Guard® will run through a short system check. The system check will sound the buzzer and flash the light mounted on the control module. After the system checks are complete, the green Power light near the override button will be illuminated.

During operation of the EWP controls, the Crush Guard® monitors the force applied on the wire rope. If the force applied to the wire rope exceeds 1 – 2 kilograms the alarm will trigger. The wire rope is anchored to the frame via a magnetic release. If force continues to be applied to the wire rope, the magnetic release will break away removing the tension on the wire rope and preventing the operator from being crushed against the controls - or injured by the wire rope.

The two vertical support posts attaching the wire rope are attached to spring hinges. In the event the operator is pinned against one of the vertical support posts, the post will give way and trigger the alarm. It will return to the normal vertical position once the force on the post has been removed.

When the alarm is triggered, a cutout signal will be sent to disable the EWP controls and/or stop the engine. The light and buzzer on the control module will activate when the alarm is triggered. The light and buzzer on the control is mounted in a position where it will be visible and audible to personnel on the ground.

Once the alarm is triggered, there are two methods to return the EWP to normal operation: reset or override. To reset the system, the operator needs to return the magnet to the anchor position to apply tension back onto the wire rope - and then push the reset button. This will reset the system and allow the operator to restart the engine - and once again operate the EWP.

If the operator has been pinned against the controls by a crush hazard and can't attach the magnet back to the anchor position, they will need to override the system. By pressing and releasing the override switch, this will cause the light on the override switch to flash and disable the cutout signal for 30 seconds. This gives the operator time to restart the engine and move the EWP away from the crush hazard. After 30 seconds the override light will stop flashing and the system will re-engage the cutout. 

Under some circumstances the magnetic release may break before the alarm is triggered. This will not affect the safety functionality, as the alarm will still trigger and cutout the boom movements.  

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