Datian MLD1-50 mechanical line leak detector is a membrane slice selectable device of submersible pump to carry out the supervision to the oil pipelines between the conveying pressure 1.4～3.5KPa. it can automatically carry out the supervision to the flow speed over 11.4L/min or pressure les 0.6KPa pipelines. If existing leakage, through the internal piston valve and let the pipeline flowspeed limit at 11.4L/min and let the oiling users know the oil conveying pipeline exist leakage.