Two-line centralized lubrication systems are chiefly used for the lubrication of machines and plant with a large numbers of lubrication points (up to over 2,000).
The lubrication system consists principally of the pump , one 4/2-way or two 3/2-way change-over valves , the two main feed lines, the distributors arranged close to the lubrication points, the lines leading to the lubrication points, switch gear at the line end, the pressure gauge unit and the controls. A pressure relief valve is required to protect the pump from over pressure.
It is used widely for Smelting plant, rolling mills, mining power stations, cement works, sugar refineries, breweries, construction machinery, etc.