Unidirectional Setup

The picture below shows the shearer leaving the TG and the shields starting to pull.

Half-Web Cycle – Step 1 – Cutting Tail to Head

When the shearer has traveled far enough and enough shields have advanced, the conveyor push will begin to follow from the tailgate toward the headgate. Some of the shields at the TG will push to completely so that the shearer can snake back in to a “full-web” cut when it re-enters the tailgate on the next pass. The number of shields that push completely is determined by SRB parameter “Snake push”. After that, the rest of the shields will only push to the stroke set by SRB parameter “T->H Push Stroke”.

SRB Parameters "Snake Push” “T->H Push Stroke”

This stroke setting determines how much of the web is cut when traveling back to the TG on the next pass. For evenly balanced half-web cutting, this should be set to 50%. It may be preferable to change this value depending upon the grade of the seam and the conveyor loading. The picture below shows the longwall state when the shearer reaches the headgate.

Half-Web Cycle – Step 2 – Shearer at HG

All shields except at the headgate have been advanced. The tailgate is fully pushed; across the face the conveyor has been partially pushed; in the headgate the conveyor has not yet been pushed. The conveyor has a double snake and the coal seam is straight (no snake).