Hi,

I have an industrial gearbox which holds 440L of oil. The electronic level sensor is near the bottom and typically we need to drain the gearbox to replace the sensor. We trialed using a vacuum hoover in a hole at the top of the gearbox to suck out the air and create a vacuum inside the gearbox. When we removed the level sensor at the bottom, no oil escaped from the gearbox, not a drop. I would like to know which vacuum pressure is required to prevent the oil leaking out when the sensor is removed. Obviously if the hoover were to malfunction during this procedure the oil would start to flow from the sensor hole. I want to create a valve where I can lock off the valuum pressure and monitor with a gauge but I don't know what pressure we need to achieve to create a safe working environment.

Thanks

Glen