Metering Cartridges precisely control the quantity of lubricating Oil going to the lubrication point. These are suitable for intermittent operation. They operate on the principal of a positive displacement piston pump. The design is such that each time the pump is put on the discharge fixed predetermined quantity of oil. The pressure relief valve allows the oil pressure in the system to drop to around 1 Kg/cm2 each times the pump is put off. This allows the piston in the cartridges to retract. Thus charging the cartridges for the next dosage. During the next ON time the oil pressure in the line forces the piston thus discharging the previously charged oil. A minimum pressure of around 8 Kg/cm2 is required for operating the piston in the metering cartridge.