Using Centralized Lubrication Systems

"What are the advantages and disadvantages of using a centralized lubrication system?"

The use of centralized lubrication systems for supplying either grease or circulating oil to components requiring lubrication is increasing dramatically. These types of systems are now used on mobile and stationary industrial equipment, on process and production line equipment, and on machine tools.

There are many advantages in using centralized lubrication systems, including:

• Improved machine reliability
• Reduced labor cost for lubricant application
• Reduced machinery downtime for lubricant application
• More efficient use of lubricants
• Reduced cost of lubricants due to efficient use
• Improved overall lubrication of machinery
• Reduced lubricant waste through controlled consumption
• Potentially cleaner plant facilities and machinery due to reduced spills

There are also some disadvantages, particularly if operations and maintenance personnel fall into the common trap of believing that a centralized lubrication system will solve all of their lubrication problems and cease to carefully inspect and properly maintain the system.

A second disadvantage is that a poorly designed or maintained system may cause some personnel to incorrectly adjust system components and create further malfunctions. The point to remember is that a centralized lubrication system is another machine component, and it must be periodically inspected and maintained like any other.

A basic centralized lubrication system consists of a reservoir (to hold the oil or grease), a pump (to provide flow to the system), a control valve (to direct lubricant through various lines), a metering valve or valves (to measure and direct the necessary lubricant to the lubricated components), and a relief valve or line (to allow excess lubricant to return to the supply reservoir).

In some systems, called direct systems, the pump serves to pressurize the lubricant and also to meter it to the application points. Others, called indirect systems, use a pump to provide pressurized lubricant but with metering valves at each application point.

There are two basic types of indirect systems: parallel or series. Parallel systems, also called “non-progressive” types, use metering valves that are actuated by a pumping system that brings the main distribution line up to operating pressure. The metering valves operate simultaneously.

Series or "progressive" systems contain metering valves in line. After the main line is brought up to its operating pressure, the first valve operates, and then lubricant flow passes to each succeeding valve in turn. In this system, if one valve fails, they all cease to operate.