Industrial Maintenance Solutions

Intermittent motion compressors, or non-continuous flow compressors, include screw compressors which are categorized as medium flow and medium pressure compressors when compared to other compressor types based on pressure/flow charts. The screw compressor gets its name from the two screws it contains, one of which is mounted with the prime mover (motor, turbine) and the other is driven. The screws are mounted together by gears and rotate in opposite directions to each other, squeezing the compressed air with oil in the compression zone to raise its pressure according to the direction of rotation of the driver (counter-clockwise). During operation, the compressed air is mixed with oil (flooded type) inside the compressor. The compressed oil and air are then separated in an oil separation unit, with the air being removed to the discharge line and the oil being returned to the oil filter for filtration before being returned to the suction of the compressor. This compressor type is kno...

BY AMIN ALMASI. Surge can be a major challenge for turbo compressors. Operation in the surge area will result in instability, exposing the machine to destructive stresses and forces, high vibration, and even serious damage. Surge during shutdown (trip) has been reported for many turbo-compressors. This is particularly possible if the machine operates at high head and low flow, immediately before the trip, when the operating point can move toward the surge line and even pass it during coast-down (when the turbo-compressor reduces flowrate). When a turbo-compressor experiences a serious alarm, an emergency shutdown is usually initiated. But an immediate shutdown could result in a surge. In this case, the surge happens shortly after the shutdown (trip) and at a high energy level. This could be a surge at a high head (operating point could pass the surge line at high head). In many cases, there are advantages to not removing the driving power from the turbocompressor (tripping) immediately...