The Positive Displacement Injector (PDI) lubrication delivery system was developed in 1937 by Lincoln Industrial Corporation (now part of SKF’s portfolio and known simply as “Lincoln Industrial”).The PDI (which can also be categorized as a Single Line Parallel system) was designed to accurately displace metered quantities of oil or grease in a cyclical manner in small- to medium-sized industrial equipment.
In contrast to Single Line Resistance (SLR) and Progressive divider-type systems, each metering valve—or point—of the PDI can be set independently, adjusted or easily changed without affecting the system design. This allows additional injectors (lube points) to be added into the system later, without the need to re-engineer the entire system.
How This System Works
The Pros & Cons
Because it can be used with oil and grease, does not require much system engineering and allows additional points to be added easily, the PDI system has long enjoyed a reputation as both a versatile and universal system.
PDI systems that use fixed injector-displacement caps are preferred over types that permit the user/operator to readily adjust the piston output via an external adjustment wheel or lever on the side of the injector. User/operator adjustable injectors are easily tampered with—and can lead to over- or under-lubrication conditions unless they are access-controlled.
Although a main open-line failure can be detected through a time-out switch located at the end, no secondary-line failure device has been available for these systems. Users must perform system-line integrity checks as part of their PM programs.
The July/August issue of LMT will feature Dual Line delivery systems. LMT