There are four outlet feeding ports of VSL4-KR of two line metering device, inlet ports are connected with supplying oil pipes, lubricant is transferred and powered by a lubrication pump. The change-over valve connects main line to the lubrication pump, thus pressurizing the lubricant in this main line. The control piston moves in the direction of channel near the indicator, displacing the lubricant ahead of the control piston into the relieved main line.
When the control piston uncovers the connecting passage, lubricant is transferred to the left end of the dispensing piston and displaces it to the right in the direction of channel in the vicinity of indicator. The lubricant ahead of the dispensing piston is transferred via the connecting passage to the lubrication point. With the dispensing piston in its terminal position, the pressure in main line will continue to rise to reach the preset change-over pressure of the two-line system. At this stage, the change-over valve will once again cause a pressure changing-over in main lines and the cycle will be repeated as described in stage, then two line metering device VSL4-KR finishes the completed working cycle.