EEHA Automation implemented the following enhancements.
The addition of Green/Red Lighting System along the length of the BSL Area.
The new lights are controlled by three components.
- Communications with the Shearer. – If the shearer is too close to the Maingate the lights turn Red.
- Communications with the Roof Support Chocks. – If movement is detected on the first four chocks the lights turn Red.
- New push-buttons at the Conveyor Boot and Maingate Areas. – Modification to the procedures such that a Maingate operator must walk the full length of the BSL area ensuring it is safe/clear then hit the new push-button at the Conveyor Boot.
This would set the area lights to Red flashing. Alerting staff of the imminent Maingate advance.
He would then return to the Maingate, perform the advance, and press the new MG button. The lights would return to green.
Compliance could then be monitored contrasting the push-button operation against the chock movement.
The existing positive communications remained in place.
Staff are now more aware of dangerous times to be around the BSL area, and management can monitor MG Operators Compliance.
The previous controls consisted of positive voice communications; where a person wanting to enter/exit the Longwall would make positive communications with the Maingate Operator prior to entering the BSL Zone. In addition to this the Maingate Operator would have to walk the length of the BSL to ensure that no-one was in the way prior to performing an Advance.
The basics of Longwall operation.
Two roads are cut either side of the coal seam. These are called the Maingate and Tailgate (MG/TG) roads. They are typically 1-4km long and separated by 200-500m. The Maingate road houses a conveyor which transports material to the surface.
At the end of the Maingate and Tailgate roads they are connected by a series of Roof Support Chocks. A Shearer runs in front of the Roof Support chocks.
The Shearer cuts the coal from the Coal Face dropping it onto a Conveyor (called the AFC Armored Face Conveyor). The shearer will traverse from the Maingate to the Tailgate and back again. Once a cut is complete the entire Roof Support structure advances and pushes the Shearer and AFC and all Structure forward.
The AFC moves the cut coal towards the Maingate Road. Once at the Maingate the coal is transferred into a Beam Stage Loader (BSL) which crushes the coal and puts it onto the Maingate Conveyor to be taken to the surface.
Access to the Longwall is through the Maingate Road.
This is dangerous for a number of reasons.
- The BSL and Maingate Conveyor are in the same road; When the Roof Supports advance they push all of this structure forward. During this time a worker could be squashed between the wall\roof of the Maingate Road and the advancing equipment.
- When the Shearer is in the Maingate Zone fly rock can be sent into the BSL Area.
Human Nature leads to short cuts being taken. Maingate Operators only partially walking the BSL Area, or frustrated staff, not being able to make positive contact with the Maingate Operator, entering the BSL Zone anyway.
In situations where you are forced to utilise procedural controls, having a compliance monitoring system leads to less short cuts and greater safety.