screenman

A screenman operates vibrating screens or rotary screens at a coal preparation plant, controlling the separation of raw mined coal into commercial grades. The coal enters the screen at the top, and gravity combined with the screen's motion causes smaller particles and fines to fall through while larger lumps travel across and discharge at the lower end. This primary job is straightforward in principle but demands vigilance because screen performance directly affects product value and plant throughput.

Coal screens come in several types. Vibrating screens with rectangular decks use high-frequency oscillation (typically 1200 to 1800 vibrations per minute) and are common for medium-duty work, handling feed rates of 100 to 500 tonnes per hour depending on deck size and screen mesh opening. Rotary screens, which are large cylindrical drums inclined at a shallow angle, operate at lower speeds but suit high volumes and wet coal. The screenman monitors flow rate, adjusts feed distribution across the deck width, and watches for material bridging or moisture buildup that reduces separation efficiency.

The term reflects the coal trade's historical language. Before mechanized screening, manual labourers did the work with hand-held mesh; the machine operator inherited the job title. In modern collieries and coal washeries, the screenman often works alongside other preparation staff, coordinating with the jig operator and the product grader. Shifts are typically eight hours, and the work involves standing at control stations with clear sightlines to the active screen.

Screen mesh sizes range from coarse (say, 150 millimetres) at the primary stage down to fine (3 millimetres or less) for recovering slack coal. Choosing the right mesh opening and screen speed is crucial: too coarse and fines waste; too fine and the screen clogs with moisture or fine coal dust. The screenman must judge when to clean or replace a worn mesh, a task that usually requires stopping the plant and working with fitters.

Common problems include uneven feed distribution, causing one end of the deck to overload while the other starves, and material sticking to the deck due to moisture or oily coal. Worn deck surfaces or torn mesh allow product crossover, mixing grades and lowering saleable value. A competent screenman learns to read these failures from vibration patterns and material behaviour and calls for maintenance before quality degrades significantly.