A single-line lubrication system is a type of lubrication system in machinery and equipment that is used to provide a continuous supply of lubricant to various components.

A metering valve is mounted on the main line connected to the pump. The metering valve has a certain resistance to pressure shocks, after which the pressure is built up and the pressure delivers the established lubricant to the lubrication point. When the system is depressurised, a certain dose of lubricant is replenished in the metering valve for the next lubrication.