Liquid transfer compressor

To transfer liquid from one container to another, one can use a gas compressor to move the vapour that resides above the liquid.

The required compression ratio is usually low, since it only needs to overcome the difference in height and some pressure losses. The residual vapour may be flared off, but it is better to recover this gas by means of a vapour recovery unit.
This type of compressor is often used on chemical tankers, chemical trucks and railroad chemical loading bays.